ATISTRACT

The hydraulic and anatomic principles underlying the design of a prosthetic valve have been discussed as Well ae the criteria for the choice of the best prosthetic material for its manufacture. The Vammeramith mitral prosthesis hes been described in detail and the results of 33 replacements performed innammeremith

Hospital were analysed.

The Fammeramith valve was tested in the pulse duplicator in order to evaluate both its hydraulic performance and its dynamic) characteristics.

Postoperative haemodynamic measurements were obtained in 12 patients by right end left catheteritiation and the performance of the valve in vivo was analysed. The pressure gradients corresponding to varying levels of fluid flow were measured with the VcrIllan pulse duplicator and pressure/flow curves constructed. The valve was found to offer little or no resist- ance at levels of flow neoessary for body needs during rest and ordinary activity. Turbulence was detected only with flows exceeding nine litres/ minute and vas =teal just dietal to the prosthetic trap-door. The hydraulic performance of the valve in the human body was analysed and vas found. to compare well with the experimental findings. The time necesaary for the valve to open and close was measured in the pulse duplicator as well as in human beings. The opening; time was found to be 5 to 10 minim:lends and the closing time 15 milliseconds. The sounds produced by the valve were recorded and correlated with valve action in the pulse duplicator. The effects of excision end replacerent of the mitre''valve anpara.. tus on the physioloc, of left ventricular oontraction uas examined. The movement of the atrio—ventricular ring and the first derivative of the leftvontricular pressure pulse were not altered by valve replacameat. 'The conclusion in, therefore, that the rammernmith prosthesis is hydraulically and mechanically adequate for mitral . The action of the Starr—Edwards aortic prosthesis was examined by high speed cine films in the pulse duplicator and' by phonocerdiography in conjunction with aortic pressure tracings. The brill of the valve was found to spin all through the opening phase and to bounce a variable number of times acainst the tip of the cage producing multiple opening sounds. A large number of extrasysteles did not open the prosthesis. It was therefore concluded that establishing regular anus rhythm is important in the postoperative period.

AT 3

The author wishes to express his deep gratitude and thanks to Professor J. P. Goodwin who supervised this work and gave invaluable advice and guidance throughout the period of study He also Mowed the author to use the facilitiee of the Department Ciinical'Cardiolocy, at Eammersmith Lospital and permitted the study of his patients. The author also gratefUlly acknowledges the help of Dr. E. D. Rsfiery, for providing the high speed tine camera, for helping in some haemodynamic studies, and for his useful criticisms during the preparation of the eoript. Thanks ore also due to Dr. D. G. Melrose for providing faoilities in his Deparimmt for some of the experiments, Dr. R for allowing the author to use his pulse duplicator, Dr. L. Prager and Dr. C. M. Oakley for their useful advice and criticisms during the writing of this thesis. The author is also indebted to Mrs. P. Sym, Mr. G. Rainbow and Mr. R. Fautley for their technical assistance. He would also like to thank Miss Venice Lubell for her patient typing and re-wing of this thesis. CONTENTS

Abstract

' Acknoiledgements

Chapter I The Natural History of Valyular Disease of the Heart

Prosthetics in the Surgery of Mitral, Aortic 16 and Tricuspid Valve Diseases

III Hydraulic Considerations in Prosthetic Valve Design

Anatomical Considerations in Valve Design and 55 Implantation

The Choice of Prosthetic Material for Artificial Valves

VI The Design of Prosthetic Valves 94.

VII The Hammersmith Prosthesis 100

VIII The Experimental Evaluation of Prosthetic Valves 118 Chapter Dal

Experimental Evaluation of Iammeremith Valve 127 Performance

Clinical, Haemitreamio and Iviceardiographic 15k Evaluation of Patients After Hammersmith Mitral Valve Replacement

Phonocardiography in Subjects with Artificial 186 Valves

Summary and Conclusion 227

References 234. caripm

THR NATURAL HI ST= OF VALVO EASE OF THE F'

It. is generally recognised that the definitive treatment of • valvular disease of the heart is surgery Medical treatment is of value in ameliorating symptoms and treating complications (e.g. heart failure, pulmonary oedema and bacteria/ endooarditis), but be curative. Before advising surgery, the risks of the disease, treated medically, must be weighed against the risks of the operation. Surgery can be indicated only if the operation is less hazardous than the disease. Thus, knowledge of the prognosis of valvular disease of the heart at a given stage of its natural history is essential. In this review, discussion will be restricted to the lesions that usually require prosthetic surgery for their correction.

INCOMPI=CEs The clinical course of patients with mitrel incompetence may be quite varied (Vander Veer, 1958). Mild degrees are usually associated with no symptoms or cardiac disability and may be consistent with a normal life span. However, even mild mitre' incompetence is apt to be complicated by bacterial endocerditis. T3Ven if this is successfully cured, it usually leaves the patient with a severe degree of mitre/ incompetence that may later be symptomatic. Levine and Harvey (1959) and Freidberg (1956) expressed the view that there are two groups of patients with mitral incompetence: one showing rapidly progressive severe symptoms whose prognosis is poor, and another with a prolonged, stable, and benign course and better prognosis. Wood (1956) estimated the period between the original attack of rheumatic fever and the time of onset of symptoms as a little more► than 19 years, Wilson and Lim (1957) in a follow-up of 392 patients with mitral incompetence with no symptoms found the overall average annual mortality rate over ages 20 to 52 to be 2.76 per thousand per annum, The annual mortality rate for the general population was calculated by these authors to be 3.1 per thousand per annum. It would therefore be expected that many patients with mitral incompetence would survive until old age. They also found that the survival rate for patients with mitral incompetence was 97% at the age of 30, 96% at 35 and 95% at 40; these values were similar to the observed survival rates of the same age groups in the general population. Bedford and Caird (1960) stated that the dominant haemodynamic lesion in the majority of elderly patients with mitral valve disease was mitral incompetence, and that at whatever age the incompetence developed, whether, in childhood or in middle age, it represented a benign form of rheumatic heart disease. The advent of symptoms changes this picture completely. Wood (1956) stated that once symptoms appeared in mitral incompetence, the patient needed 5.3 years on the average to reach the state of total incapacity. Wilson and Greenwood (1954) found that 77 of 85 patients with mitral valve disease and (91n and 91 of 100 patients with mitral-Walve disoase and heart failure (91'A is ire dead ti 5 yeans of the ontet-orincompetence.'

AORTIC lycUIPETEXCE: The prognosis of aortic incompetenr depends greatly on the stage or the disease, severity of the lesion and the age of the patient. Usually, tbere is a long latent period between the development of the lesion and the start of symptoms, but the length of this latentperiod depends on the severity of the pathological process. Segal et el (1956) estimated that if a patient suffers rheumatic, fever at the ago of 13, he may develop haemodynmnioally significant aortic incempetence by' the age of 20 and may remain oymptom-eree for up to 10 years. They found that the average patient with rheumatic aortic inoompetenco remained in the symptoomtic phase for 64 years before death. The average duration of the symptomatic phase for gyphilitic aortic incompetence was 2.5 Years. It should be emphasized that moderately severe aortic inoompetenoe may be present for many years with no evidence of cardiac decompensation or disability and in a few patients thin asymptomatic period may extend for as long as 20 to 30 years (Segal et al, 1956; Evans, 1964). Bland and Wheeler' (1957) followed up 87 awmptomaile young patients 'with severe aortic incompetence for 20 pars. They found that after 10'years, 35 of them were still well and 38:: were dead, and that after 20 years, 26;,44 of the group were still well and 5.1: were dead, tbod (1956) eatimated the average life expectancy of rheumatic aortic incompetence as 20 to 30 10 years from its development. Thin longasymptamatio phase may, however, be interrupted suddenly by ono of two hazards. rive per cent of patients with apvere aortic incompetence who are fairly well compensated die euddenly and unexpectedly, possibly as a. result of sudden arehythmias (Segal et al, 1956). Levine and Tlaryey (1959) stated that during follow-up of approxlePtely 500 patients with severe aortic incompetence (mostly rheumatic), sudden deatIveas as oommon an 25 (i.e. the same as its Presume, in aortic stenosie). Bacterial is another hazard and may. change a mild lesion into a severe one. It is generally agreed that once aortic incompetence starts to be symptomatic, the course is rapidly doenhill (Cabot, 1951; Segal et al, 1956). The association of angina and congestive heart failure bears a grave prognosis and usually occurs in severely incapacitated patients. Other signs of poor prognosis are prolonged circulation time, low diastolic pressure, long Nat interval and inverted T waves in the eleotrocardiogram (Segal et al, 1956). Tvo important Motors must, in addition, be considered in assessing the likely clinical course in an individual patients the age of the patient and the duration of the existing symptoms.

On the other hand, Bedford and Caird (1960) noticed a close oorres. pondence between the survival of 136 patients with isolated aortic incompetence above the age of 65 and of a comparable hospital control, group. Mart failure, however, greatly worsened the outlook. They concluded that isolated aortic incompetence in patients above 65 years of age carries no aftersapregnostio significance unless there is evidence of "hurt failure. It could be argued that these reaults re misleading and represent only dither very miltlrheumatio patients' surviving to old age or piAients with only. slight aortic Valve deformity from aortic dilatation or atherosolerosia of the valve cusps developing in old ago. Cases of non-rheumatio'aortio AnooMpeton c present spe problems. Syphilitio sortie incompetent* has a core serious progaosis than rheUm... atic aortic incoMpetenoe. The poorer outlook in luetic cortiiincotpet- once is largely dependent on the greater severity of the lesion, but in come measure it depends also on tbsextent'to which sorties involves the orifices of the coronary'arteries (Evan's, 1960: The prognotis ia also worse in tho cases due to bacterial endooarditis as great destruction usually occursbefere'the process can be halted by treatment. The prognosis is also serious after rupture or avulsion of a cuap has occurred. Complieations of aortic incompetence are practically li xite d to tacterial,endoearditis (rood, 1956).

41ORTIC STENOS18: .As in most other valvular diseases, even tight aortic stenosic can be present for a long time before apy amtmcs develop, but about 18 to 25;x' of the patients die abruptly without immediate warning, presumably from ventricular fibrillation and standstill, whether they are symptomatic or not (Mitehel et el, 19544 Levine and Harm, 1959). This means that aortic stenosic carries a Mortality at about Mr. and, •12 • on this account alone, it is worth surgical treatment. Once patients develop symptoms, the prognosis becomes even more gloomy. The average life span of a patiemt with aortic etenosis after development of heart failure, syncope, and angina is 2.0, 3.3 and 4.1 years respectively (Vitchel et al, 19541 Wood, 1956). Lowia (1951) found an average survival of only 14 months in 25 patients after the first symptoms had developed. Bergerson et al (1954) stated thats "within two years of the advent of any symptom, one-half of the patients had died. Less than one-fourth of the patients survived the onset of those manifestations by five years." Men atrial fibrillation occurred, the deterioration was much more rapid and only 25;"'; of such patients survived one year. Ellis et al, (1957) concluded that atrial fibrilla- tion was just as ominous a development as left vestriculmrfailure. They oemmented that when either left ventricular failure or atrial fib• rillation was accompanied by cerdiac pain, death followed Within weeks or months. Harken et el (1959) followed up 54 symptomatic patients who were advised to have surgery but refused for a variety of reasons, and found that six months later, 49 of them were dead. Hoy:ever, many of these were very advanced or terminal oases.

A less gloomy prognosis was given by Grant (1933) who found that 14 of 35 uncomplicated cases survived 10 years, 7 of them without nificant deterioration. Olsen and Warburg (1950) followed 42 patients with an averaco age of 53 years for 6 to 23 years. The mean survival after the first cardiac symptom was 8.8 years, but the range of survival vas vary great, being up to 12 years in some cases. Kump and Bean (194) .13. mentioned that a considerable proportion of their patients had either numerous episodes of congestive heart failure or chronic failure lasting up to 12 years.. Heart failure accounts for 30..to5C of the deaths (V'tood, 1956) and bacterial endocarditis used to account far,2Cof,the mortalities (Mitchel ©t al, 1954).':though its toll, must be much less now. Vood (1950 analysed. reports of 6k patients with aortic stenosis:not operated. upon for one reaswor'another and found. that at least 2$ dead at the end of the follow-up period of -I.:marsand 25ri; were unchanged. As the rest of the patients were lost to the follow-up. the Mortality could well be double this figure. :All these patients were eyeptomatio when first seen.. In a:study of survival figures of 129 patients with aortic stenosis above, the age of 65, Bedford and Caird (1960) found that their survival differed very little from the predicted survival for the same age group in a hospital population. without aortic stenosis, and that after the first year it was not.much greater than the,natural (i.e. general ,pop- ulation) expected survival.at this age. They,conoluded that aortic stenosis.per se does not carry any substantial mortality in the elderly end that its prognosis is good. If heart failure is present the cut- look was worse, but still differed little from that of heart failure in old age-due to ether causes. On the other hand. Dry and Uillius (1939) found that the total mortality of aortic etenosis increased in a linear manner from the third to the seventh decade, otter which it fell again; but there were no many deaths in the eighth decade as in the sixth. The average age of death in their, patients s 55 o' 65 ;years, with the females dying earlier than the males. COUCLUSION: Review of al history'of mitral incompetence, aortic, incompetence and aortic stenosis,suuesta that patientia remain'asymptom. atic- for relatively on,; periods of tins. In this phase of ems natural history the irmediate prognosis is generally good:and the patient can pursue a useful occupation. without much disability. The length of the asymptomatic, phase depends on several-footers; the most important of these are the severity or. haemodynamio-disturbanoo-reault. ing from the valvular pathology, and •the,funotional stato'of the mocardium. One exception to this general rule is aortic stenosis which carries a 2Crisk of sudden death even in the haymptodatio phase Ulan symptoms appear, the course becomes rapidly downhill-and the :Life, expectancy becomes poor. The length of the'-final stage also varies, but is usually between 2 • 5:years; ,beingshorter in aortic stenosis than in other lesions. Medical treatment does not appear... to be of value in the initial asymptomatic phase. In the advanced etageS, medical treatment is of treat help.in ameliorating cardiac failure, in revereing aoutepulmonary opdemavand,in preventing complications. However, there ia no definite • • evidence that medical -treatment prolongs life or prevent the flnal incepapity; ancialthough initial attacks of heart failure or—pulmenary oedema may respond well to therapy, subsequent attacks are usually more resistant to treatment and finally the pationt:m4y lapse into. irreversible 15 .- hurt failure and chronic pulmonrry oedema in spite of adequate therapy. Surgery. is at the preseht, ths only definitive form or treatment available. Owing to the high risk of the operations, surgery has not usually been advised e7;tept in the symptomatic phase. Eowever, this preetiee or delayed surgery. adds to th© rialcei' operation. as it entails operating in. patietto With advanced pulmonary vascular changes, and myocardial atrephy and fibrods. ' Aa Confidence in the, operative techniques grows and as tie operative resulta beteMs better, more ptients are divined to undergo Surgery at= earlier phase It is' ConelUded that patients thould'be advised to undergo, surgery When' their olinieal, cardiographic and radiological findings-shot' evidence of in- ore site, but before they have lapsed'into the rapidly down- hill' course. At thiS Steve the heart muidle is still in a good state and can cope with the effects of perfUsion 01 of aort periods of myocardial isehaemia that maY'oecur during the course of orration. In addition, the patients will he free from the electrolyte and metabolic disturbances which may follow prolonged and intensive therapy. — 16

Cl/AFTER 1;

tali .CIa' RI:" . AORTIC AIM Tiu spID DISNAITz

INCOMPETENO

fitperimentc i fork on valvularsurgerY'vas carried out n s far back an 1876 by Meat. ' Since then, and'until very recently, gery for mitral incompetence Wes directed along two main lines. first approach involved.the reduction -of the size of the patrol annulus (annuloplesty). The techniques used ,to achieve this, consisted of:encitclin the mitral ring with aligaturo:of silk (Cushing and nranoh,'1908) or umbliosl tapo:(Davila et al, 1954), or plicating the annulus at the site of the commiscdres'(Bail4 et al, 1954; Kay and. Ctoes, 1955; Nicola, 19571 dine and Brom. 1957; Lillehei et el, 1958). Start et al (1962) auggeatod in he with marked dilatation of the annulus and a large flexible aortic leaflet of the mitre' valve, annuloplasty might give excellent results, at least as a means to postpone the need for replacement of the valve in young people. The second main method used to correct mitral incompetence wss to supplement or replace deficient leaflet tissue. rost or these efforts were directed towards the posterior leaflet which is the usual site of maximal leak. IbEtending the cusp tissue was done either by - 17 -

the use of pericardial or vein grafts (Murray et al, 1938; empleton and Gibbon, 1949; Bailey et al, 1954; Cleland, 1966); or by the use of plastic materials like Ivalon (Effler 1958; =chat et al, 1958). Complete replacement of the posterior cusp was attempted by McKenzie (1960) using a silastic monocuep; and by Schimert et al (1961) using silastic covered Teflon felt with artificial chordal, of the name material. Replacement of the anterior cusp with its chordae by a mobile prosthesis was attempted by King et al (1960) using knitted. Teflon. In spite of few favourable reports, it is now generally recognised that not all diseased valves are suitable for plastic procedures. Patients with a calcified, deformed, rigid anterior cusp with shortened, fibrotic or even oalcified,ohordae defied attempts at correction' Any corrective procedure on the anterior cusp must start with a mobile cusp of reasonable shape than can be enlarged by the use of grafts or plastics. Those corrective procedures took a long time and involved a good deal of trauma during manipulation of the heart. It was difficult to judge the competence or the hydraulic performance of the corrected valve at the time of the operation and over- or under-correction were not uncommon. Another reason for failure was that commonly, the leaflets were too soft and friable to hold sutures. If they were strong and thick they were also too rigid to open and close properly. Problems of acceptance of foreign tissue and the occurrence of thrombosis all added to the already difficult situation and many workers started to search for a prefabricated valve that could be pre-tested for all the important characteristics and then inserted in a short time knowing beforehand what its performanoe - 1.9 polyurethane reinforced with dacron together with artificial ohordae made of Teflon. Key et al (1961) used a Teflon sleeve valve with Teflon chordae in human beings. 4 DALL..AND...CAGE PROSTHESES: Following the lead of Bafnagel et al (1954). Rerun et al (1957) experimenteO with a ball..end...cage valve in which Theban. was made of luoite and the cage of Teflon. Harken et al (1960) lore the first to Ulla abell.end-cage valve inhuman beings, composed Oa stainless steel cage and lucite or silastic ball. This design was greatly popes:4601 by Starr (1961) who after experimenting with several designs and using several materials, finally settled for a ball...and-cage prosthesis. It consisted of a highly polished cage of silicon-covered vitallium enclosing a solid silicon rubber ball. Fixation was achieved by means of a margin of knitted Teflon cloth. This prosthesis gained immOlate popularity.. Its mitral and aortic versions are probably the most commonly used. prosthetic valves nowadays. Several important modifications on the basic ball-and..cagn design have been attempted. Megovern and Cromie (1963) designed a self..retaiMngball..and-oage prosthesis. Multiple curved pins round the Titanium ring can be made to protrude and penetrate the mitral or aortic annulus, keeping the valve in position. The Magevern valve employs an 'Talon ring for fibrous tissue ingrowth and is made intirely of Titanium to eliminate problems associated withalloys (DeBakey et al, 1965). This design has greatly .20. simplified the technique of placement and fixation of the prosthesis and reduced the time during which a pump oxygenator is used. Both factors may be of crucial benefit to an already weak myocardium. If the position of the valve is unsatisfactory, thepins can, be retracted, ,and the procedure repeated* Additional advantages of thievalve are the elimination of the cloth fixation ring and of sutures, both of which are favourable sites ar formation, It also has a larger hydraulic orifice for the same external diameter, but is a good deal heavier than the Starr-Edwards valve* Magovern et al (1963; 1964) reported the successful use of this valve in 52 patient., undergoing aortic replacement and in 8 patients undergoing mitre replacement, There had been no migration of the prosthetic valve and good fixation had been achieved. Frequently, however, incompetence occurred from a leak around the pins, especially if the site of fixation was irregular. A thin silicon (surf was added to the outer circumference of the upper plate to overcome this difficulty (Magovern et el, 196th.). or the 8 mitral valve replacements attempted by Magovern et al, there were 2 operative and one hospital death. To overcome the problems of thrombosis, two modifications of the Starr Edwards valve have been made. Starr ax. Edwards (1961) noticed that thrombosis appears first on the atrial aspect of the none of fixation of the mitral prosthesis and then extends over the prosthesis by direct extension rather than by multicentric formation, It reached the valve inlet 2 - 3 days after implantation and produced occlusion of the valve orifice within a for days following insertion. They found that the ar4e4stration of antiooagulan did not prevent throMbna formation in the vest majority of patients. Working on the assumption that throm- bosis is favoured on the atrial side because of the exposed sifts* line and the irregular eurface, they devised the °Shielded Prosthesis" in ehich a silicon rubber shield attached: to the prosthetic valveving covers the atrial side of the suture linerna. the surrounding sone of injured endo- cardium. There are no reports of the use of this design in human beings. Cartwright et el (1963) noticed en area of turbulence that existed above the ball during . There appeared to be sufficient stasis in this locality to permit fibrin and other blood elements to cling to the struts of the cage. To reduce the amount of cage structure in.the area of turbulence and eliminate crossing struts which may serve as a lattice work for clot formation they devised a valve with en incomplete cage. Gott et el (1961; 1962) suggested coating the bell prosthesis with colloidal graphite in the belief that this substance would impart extra smoothness and water repellency to the surface of the prosthesis. It also carried a negative surface charge (Zeta potential), (see paseg7 ) whteni vas thought to discourage the occurrence ar throtbosis. Other workers could not confirm these claims (Mirkovitch and Akutsu, 1963). The results of mitral valve replacement by a ball.and-cage valve have varied in different centres. The mortality rat* has tended to become smaller with the increased experience gained bytime and now ranges between 3 and 50.7. (nfler and Groves, 1963; ugh, 1965; Lillehei et al, 1965; d et el, 1966). .. 22 ..

The use of the ball-and-cage valve has been attended by seeveral complications. Thrombus formation occurs frequently, especially on the atrial side of the valve suture line and extends into the left . In some eases the clot has involved the valve orifice .and/or the ball and resulted in its immobilisation (Garamellal others, pieces of thrombus have detached and escaped into the. circulation causing peripheral emboli.. The incidence of embolism is as high as 3 in 30124, series (Herr et al,-1965). Adequate anticoagulants:0 .0 7 days after operation does not usually prevent these emboli, although it reduces the.incidence (Davila, .1965).: Infection which can occur at the site of fixation is very difficult to treat and commonly fatat (Starr et al, 1961; Ftfler, 1963; Groves, 1963; Stein et al, 1960.. Disruption of the sutures is more common after replacement of a congenitally insufficient valve as it has hot been fibrosed and thickened by a chronic rheumatic process. Dislodgement of the valve was reportedly Groves (1963) after replacement of a congenitally incompetent mitral valve. Breakage ofJhe sutures has also occurred (DeBakey et al, 1965). Both complies'. tions are usually followed. by evidence of mitral incompetence. . Deform- ation of the ball has beeh recorded more than once (Ablaze, 1965; aerie et al, 1965.)* Disturbance of valve action has been caused by projection of papillary muscles and ohordae tendineae into the prosthesis, and in one instance, this caused death (Starr, 1965). Owing to the relations of the mitre). annulus,, inclusion of the coronary sinus, circumflex coronary artery or the great cardiac vein is possible during suturing, particularly following 23

extended excision of calcium fron annular tissue. Hugh (1965) reported a patient in whom the posterior aspect or the heart was perforated during suture with resultant severe intrathoracio bleeding postoperatively. Small gradients across the Starr.Mdwards mitral prosthesis were recorded by Morrow et al (1964) and Kosdi et al (1964). In same

patients gradients of 3 - 7 Ma It wore found. The inertia of the ball duritwopening and closure was calculated by Harken et al (1962) and found to be 0.015 to 0.02 sec. for closing end opening. They also found that a pressure gradient:or 042 mm Ng was needed to open the valve. Roberts and Memo, (1966) reported a patient in atom the wyocardium protruded into the cage of a Starr-Edwards prosthesis during ventricular contraction and interferred with the free movement of the bell Studies on the red cell survival showed no shortening of the life span of the red cells after replacement of the mitral valve by the Starr Edwards valve (Brodeur et al 1965). 5 • rils9cp pilpsTplisrst One big disadvantage of the bell.end-cage valve deal is the length of cam necessary for the ball to travel clear of the ring. he long cage protrudes into the outflow tract of the left . To overcome, this defect, Henagel et al (1965) and tilliams et al (1965) independently described a valve with a discoid mechanism that needed a relatively short cage for its movement. Eufnamel eta (1965) claimed the following advantaged for the discoid prosthesis, i) Ektromely light weight ii) Short travel distance iii) Vizarno, throstbus formation iv) Little protrusion in the ventricle or aortic root 1r) Low impact on opening and closing vi) Minimal trauma to blood elements On the other hand, Beeson and Burns (1965) studied the functional characteristics of the Itufwgel discoid velve in a pulse duplicator using variable volt= and rate. They found, that, at certain rates, the discoid valve failed to close; this failure vas as high as atee. at high pressures. 6 LETITIMMAAR lyitgliarnEris In an effort to combine the durabilitar, competence and f'aoilit, of implantation of the ball.and.eage valve with the favourable flow charao• teriatios of the lenflet prosthesis, four lentioular proathe2os have been devised. The first is the ITszvnermeith valve (Bente11 at al, 1963; Melrose et al, 1964.) which will be described in detail later (Chapter VII). Another is the Lillehoi valve (Crus et al, 1965) which consists of a free floating meniscus shaped Liao (concavo-convex) of Teflon or +Mastic which is boated upon a stainless steel or vitallium base. A cage Of striviless steel or vitallium struts holds the disc in place and permits it to open up to 80 • 85° while pivoting on one aide. cuff of woven Teflon for the fixation of sutures is attached to the motel base in a groove. The floating meniscus is free to rotate 360° round its central exit and does not possess a mechanical hinge, flexian crease or joint that can wear out. Experimental work has shown very small gradients across the prosthesis at physiological flow rates even in emaller sins. 25

This prosthesis ponaesses the advantages of competence, ty and simplicity of the ball-anal-cage valve, but its flow charaeteriatice are more like the leaflet valve (Grains et al, 1965). Creme and Jones (1965) have devised a Caged lens prosthesis for both aortic and mitral valve replacement: The cage is constructed of titanium with a silicon rubber lens. A croup of f3outh African workers ha trodueed a titular prosthetis mnsiating of a stainless steel ring to which attached a suspeaaiou bar (Bernard et al, 1962 and 29651 Beck et el, 1965). The ring and bar are mated with Teflon. The ring is pierced by many boles and before insertion, is covered with compressed polyvinyl sponge. The mobile segment is made or silastic end consists of a ball in the shape of a. lens,. a stem and a arose bar. Sir mitral valve replacements sere reported in 1962 with= mortality. 7 OTHER DESICEBis Cartwright et al (196‘) introdusOd the fAeleff-Cut double caged proethesis for both the mitral and aortic valves. Cooly et al (1965) used this prosthesis in 100 patients for both aortic: and mitral valve replacements with an overall mortality of 19i. COMM: The complicated structure of the mitral valve apparatus makes its surgical manipulation difficult and sometimes dangerous. In addition, the major part of the pathology commonly involves the eubvalvular apparatus making my form of repair or plastic correction diffieult. It is also difficult to fudge properly the competence or adequacy of the mitral' °rifles under the conditions prevailing in the :operating theatre at the end' of plastic repair. 'Consequentlyi plastic procedures are sUctoessful only in a restricted number of chosen 'oases. The oomplicated anatostr also mss saaii.t a al valve rePlacement with a graft Vary difficult, and the only 'prooedure that haspreyed practioable is total rePlemenent of the initial valver with a prefabricated and pre-tested prosthesis. Of the various designs available for a mitral proethe ie.- the cusp or Sleeve Vpcia of valie are by far the beet frail the hydraulic 'paint of vieir• They also have the advantage of act introducing. a foreign body into the Ventricular 'oavitzy'during linfortanately. no plaetic so far knotm an 'Stand repetitive foldinein the he for a long period and thane designs have. beci.abemdimed until meteriale with better mechanical qualities are discovered. The ether desigoi3 can be olassified into twot mss. Cele roup'. includes. the prostheses with a cage that remains in the ventricular cavity thrOughout the cardiac ctiele (e.g. Lillehei valve; Stair-Edwards valve; Eitfaagel valve; Saaeloff.Cutter valve; eta). The objeetions to this design are maro, and include irritation of the left ventricular eeptum• interferenoo with left ventricular contraction and the presence of a larva statienary surface on which thrombosis can occur. The other group at prostheses include those in which no pert remains in the left ventricular cavilor. during systole (e.g. Hammeromith "alive and University of Cape Town 'Valve). It is believed that these deeigns are superior to the others. .27.

...A 917 v , A . AMIN STMG$IS: Wrier (19U) made the, first deliberate surgical attack on .st stenosed aortic valve by invaginatingthe wall of the Frith the, finger in the hope or dilating the, patient surVivedat least for ,,ewhile, transventricular approach to theetenoaed, aortic valvelasfirst advocated by nuithyst“1, (1948)-anlwas used, by and ethers (1950). ',Glenn (1953) reported tho erperimental • Application of digital valvotoeci througha. divertieulum sutured directly to, the aortic wall. This method was used in patients'forthe first time by Bailey et al'(1953). Utilising korpotharmia, Lori t c 1. (1956) end S, a and 'torts (1956) aocomplishod aortic-velvotopy in patients under direct vision, Lillehei et al (1956) employed a pump oxygenator for the purpose of extending the operating. time indirect vision procedures. Mader et el (1960)

reported SU00030 rith subendothelial debridement ar calcium deposits and 000011leation.of the valve leaflets in alimited nuMber of patients, but follor.up studies sugzested theta residual beemmedYnamic abnormality was commen and that recurrence of the obstructlan was rapid. Calcium emboli after aortic valvoplasty tare reported by Kirklin (1963); Waage et al (1962); -Glotser et al 11962)., and several others, , .. Holley 0,81 (1963) reported calcium emboli in 61%ofhiapatdenWerter aortic vilvotomy.— B.taLcaa172USr..MPL1: Several years before a direct surgical approach vzac made on the

incompetent aortic valve, Tufnagel et al (1950 succeeded in partielly correcting the lesion by placing a prosthetic valve in the aorta distal to the left seclavian artery. PhysiolopAcal studies (Rose et al, 1954; Roahe et al, 1956) demonstrated that this prosthesis in the deaeending aorta controlled about 75`i of the reflux through the aortic valve. A reduction in pressure in the left atrium and the left ventricle followed, as well as en improvement in cardiac output. The diastolic pressure, however though increased distal to the prosthesis, was further decreased proximal to it and coronary blood flow Meinished. Tho number of Hufnagel valves used in patients was estimated to be at least several hundred (Lindtkog et al, 1962). However, this valve failed to correct aortic incompetence completely, did not allow simultaneous correction of coexisting aortic stenoais, and introduced complications such as thrombosis with peripheral edbolism„ red cell destruction aneurysmal dilatation and rupture of the aorta at the site of the artificial valve. As a result, its use has been abandoned. Attempts were mede to constrict the aortic annulus from outside the aorta (Bailey and Likoft, 1955; Taylor et al, 1958). Temporary success was achieved in a few patients but owing to the impossibility of holding the constricting ligature at the level of the annulus, this method too, was disoontinmed. A number of techniques utilising an obturator or flap placed above the valve to obstruct the aortic orifice duriag were attempted (Bailey and Likot't, 1955), but the technical problems were too groat, and these methods were not widely used. Pith the advent of open heart surgery, definitive reconstructive prooedures on the aortic valve became feasible. Debridemeat of the cusps has been performed in eases of combined aortic -stomas and inoom- peteaco, (Mulder et al) 1963) and the transformation of a -tricuspid, valve, into a bicuspid valve has been tried (C 'serene et a.1 1958t Bailfet AIM Zimmerman) 1959). C01111Firt

71.11e encouxaging results' ble incidence of postoperative survival. have been reported by .severel authors) in oorrecting both aortic ate/seas. and incompetence) ' it was. aeon recognized :that most lesions' in +. the'diseased valves consisted of extensive fibrous and/or ealoiferous depositt which very frequently, prevented commissurettety' from ecoomplishing more. than the .production of a "crook in the concrete" end .8150 preVentol any plastic procedure from fully or permanently correcting imootrietenee (Loa) 19614., rebridoment of the calcified aortic valve is extremely tedious and time consuming and. it invarially leaves. .the valve with s. roues surface which is niaus for fibrin deposits. Frequently) debride- sent cannot be accomplished without' extensive destruction of the valve. only , rarely does. the valvular structure lend itself to effective nation by simple incision, 'dilatation and suturing (Roe, 1960. .koP.T2C VATAT:E.P,Phit,cm,r(r,

Tio, main lines dominate the current work on aortic Ve replacement: graft replacement ana prosthetic replacement.- 041Arr REPietnirr. OF TIM AORTIC pprp

Three types of grafts have been used: (1) 1Weast3a: Operations using homormarts started with the experimental *cork of Yam et al (1952). Initially all efforts were directed to placing the hemograft in the descending aorta beyond the left subelatrian artery, like the }furnace val ye, leaving the diseased aortic valve untreated. In 1956 Murray reported what vas apparently the first successful perform- once of an aortic valve homograft In human b The patient was living and well 6 years later (Iferwin et al. 1962). Derain et el (1962) success- fully inserted 9 homograft valves in the desoending aorta. /Worn work on wave homoerafts hes involved removal. of the diseased aortic valve and placing the hanograft in its pine., i.e. below the coronary orifices. Ross (1962) reported the first eubooronory earths homograft replacement in a man of 43. Ile used the technique described by Arran and Owning (1962), for removing the aortic valve from cadavers, fashioning it and inserting it in the subooronary position. The patient survived the operation. Barre.t-Boyer (1963) reported a series of 44 causeentive sortie valve replacements by freese.dried homografta 'pith only 5 fatalities. Two of the homografts were examined at post mortem and. 4. months after insertion and in both the architecture of the cusps was normal. Etre recently (1965) Barrate.Boyes et el rvorted the results of 183 aortic valve replacements by Freese-dried ha:merlins with only 11 hospital deaths (C) and 12 lath deaths. One hundred and twenty two patients were followed up for period° of 6 ► 36 months. 'Mere mare no embolic phenomena in these patients duringthe followdop; and there were 5 incidences of homograft rupture. Three patients had permanent complete heart block and 2 had bacterial endocarditis. Reoe.theterisation after valve replcoement shoved minimal or no obstruction and the maximum gradient across the homograft at rest was 22 m flg. (2) Auteprefte: The first aortic valve autografts reported were mtde ricardium. Experimental lurk was done by. Templeton and Gibbon (1949) Prochaska et, al • (1964) sucoessfully placed a pericardial automaft valve in the desoending aorta of one patient. Cineangiogrephic• studies demonetrated that the valve vas functioning, normally, and pathological,examination 10 months atter implantation did not show any shrinkage or increased rigidity of the cusps. Several authors favour the use of rasa* late, tailored to the shape of aortic cusps (Swing, 1965; Cleland, 1966). The obvious advantages *film.' • of this technique are the use of autologous (as opposed to homologous) material with loss • whence of rejection, and its availabilith as opposed to the technical diffieulties of obtaining, storing end firing the very fragile, aortio valve homograft. An aortic, valve tailored from the fascia late sus implanted in. 2 patients with severe aortic ineampetenoe in Vemmersmith Hospital by Ur. 14 P. Cleland. These patients are living and veil up to the tine of writing. (3) vetarosrafts: Duran and Gunning (1964) transplanted a hethrologous aortic valve

into a very ill patient. The patient died Z. hours later for COMB unrelated to the hsterogzeft. Blast et al (1965) transplanted sortie valves from Anlmas to humans' This operation cos done in 5 patients; all of them survived masers reported to be well three months •after the operation. -52..

PROOTHETZ9 REPLACEMENT or TIC: AORTIC VALVE: Several types of replacement have been attempted: (1) Reelacementf a„SinFle Ouse: When one cusp vas found deformed while the other two were normal (a highly unusual finding) single cusp replacement was performed by Hufnagel et al (1958); Bahnton et al. (1960); LfoGoon (1961) end by several other workers. However, the flexible virtues of synthetic cloth cusps made of Teflon or Dacron and used by these workers and others were offset by the fact that fibrin deposits occurred on this cloth and by their inevitable replacement by scar tissue or calcium which was detrimental in the long run. HUfnagel et al (1958) used Dacron cusps which were coated with silastio or polyurethane to combine the strength of Dacron and Teflon with the excellent surface properties of silicon rUbber and polyurethane. (2) .enlacement of A11 Three Comm: Kay et al (1962) used silastic impregnated cusps made as a single tricuspid unit. Roe et al (1965) used a percioion moulded tricuspid leaflet aortic prosthesis made of silicon rubber fritha metal band and. Cloth suture jacket. It had three leaflets each 0.01 inch thick. An anti-thrombogenic coating (Gott et al, 1961) could be applied to the entire surface. It was tried in 15 patients between the years 1960 and 1962 with 5 long-term survivors, the longest survival being 5 years. Other workers used three separate valve cusps (Bahnson et al, 1960; 1965). All prosthetic valve cusps (whether single or triple) suffered from common disadvantages. Their attachment to the ventricle frequently - 33 became loose with partial or total avulsion from the annulus. Tissue ingrowth and fibrin &position together oaused them to become thick ant stiff awl calcium &Monition eventuallq 000urred leading to restenosis. In addition repeated folding at the crease line caused the valve to and tears were commonly found in the cusp e. In spite of these hasards, several patients who had their aortic valves replaced by prosthetic cusp valves between flhroh and October, 1958, by Hurcagels

NeecTorn, Harken, Muller. KAY McGoon and Rahman were still living in 1963 (Roe, 1960.

(3) nin Valve ePA0MPRRAI The story of aortic ball-end,oage valve motile:sin parallel* closely that of the mitral ball-and.camo prosthesis. The valve most commonly used is the aortic version or the Starr-Edwards valve. From 1962 to May let, 1965, 10,454. Starr-FA:wards aortae prostheses were !old by the manufacturer to centres al/ over the world (Pieria et al, 1965). This valve differs from the mitral valve only in the suturing ring design which is made to fit the anatomical peouliarities of the aortic annulus. The Negovern oiliNfetairdavvalve is also commonly used. Owing to the large visa of its cage, Lillobei (1965) suggested that it should be used only in patients with a dilated aorta. Pe felt that in patients with severe aortic incompetence and small aortae, results may be better with the Starr.sEdwards valve, as the, bulky cage at the Pagovern valve will consume a large proportion of the aortic lumen leaving only a tiny alit far the passage of blood.. on the other hand Waft and Mel (1966) reported obstruction of the aortic root by a comber 8 Starr-Edwards cis in a a a sortie st 0

Complete obetruetion of the is th the cage of the preetheeis led todeatheff the patient, al " aloe orifice and the action of the boll wire not abnorPal* ery the aurgeonaluat be' ire that the area of Clearanoe betwemT the valve ball axe theiaortio Bell & equal: ar exoCide the

apace preilded lumpeyStale betiien the boll MO thO'inuor Margin of the preathesis* This spacewas called the it taranee'cone7 by art/right et al 01963). Another valve used for aortic replagement is Oartwrightosmodificatioe'df.the tarra4Mwards valve. Several eapplicatiene have been reported e`ter sortie vale replace- with the bell-end Valve* Disruption of euturee 36134int to ineempetenoe, and infection of the eutares'were reported by several verkere. of blo flow past t e sor e valves the i.ricidenee of thrombus formation is wale= the. In the slow-flan mitre' valve* The increased velocity may also be the receen "Ay a shortened red blood survival is almost the rule after caged, bell 'valve roplacemmat or the aortie valve but is not seen when the same valve is 11311d in the mitral area (Predeur et alp 1965). Bkoessive haemolysis with signs of jaundice has frequently been reported, usually in patients in whom incompetence develops from a leak through or around the prosthetic valve ring (Stevenson and Barker, 19641 Brodeur et al, 1965)* Pieria et al (1965) examined 860 Starr»Bdwards aortic velves 'which

were returned to the manufacturer after being obtained at autopsy. Of 35 these, seven bills ahoted evt.r r se injury with a of the follow. ing abnormalities: loss or in in mass, change in our, consistency and shape, and comprossion'ma R1 from Rage struts or 'elite rings.. In toe instances death was related to ball dislocation. e et al (1965) were able to reproduce these abnormalities in bal bjected' to stress in the pulso duplicator by ohneging several t a. %bey also found that malposition or the prosthesis or =when damage to the highly polished °outset surface might predispose to ball inJury. Small change in valve eonfigmwdoe end in the ouringplecess of silicon rubber also influenced the margin or oafetY Inone of our atients, a creek was found in the lass eleven months after valve inse tion, Ablasa et al the complete extrusion of the deformed ball outside eleven months after valve insertion. The bell, after extrusion 1 ged in the bifuroation of tho aorta. Hxamination of the prosthesis shoved intact well-placed, ring and cage. The ball hwever, was irregular an0 smaller in else than normal balls for the name prosthetic valve sise. lawation of the Vegovern salfretsining valve has el o been reported. Peek gradients of 10 30 mm were found across t Bdwards prostheses by ;:oe (19a). (4) New PI:orkhesem Gott et al (1960 introduced a design in which the prosthetic valve orifice was closed by two winglike leaflets that were attaohsd by a binge to a central bar that extended across the middle of the valve cringe. :Theoretically, this v vc has :seversI disadvantages, The pree(mce of a form of =ohmic l'hinge increases the inertia ,of the valve during opriong and Closing and is, liable. to mechcnioalfailute and early weer. -The positienef the central bar in the middle:of•the stream increases turbulence. • In 'addition, the meniscus valve (Lineai valve); the lent .Dinar • valve of Cross ana4onas (1965); the double caged valve (Cartwright et el, 1964) ana the discoid valve (BUfnagel, 1965; Tilliams,-:065) ar all designed for use in both aortic end mitral valve replacement. IMOD Aortic valve replacement is newmost'commonly performed thball- cndoage valves. it is generally reclined that this is not tie ideal solution. Alarm-number of complicationa are co=on to ell:variet4eo of sortie prootheses. The continuous use of anticoagulants for Jade= finite periods of time, so far conaidered esontial by most workers, is a particularly serious disadvantage. Control ,of antiodegulent therapy by frequent prothrombin time estimation is difficult ead . meY1,e impossible. Life must be lived under c continuous threat of both embolism andtaam.. orrhage, ona many z,ationts have had embolic phenomana at times then the results of prothrombin time ettimatione were censiderea satisfactory. Autopsy examination shoved that two of our patients had. thrombosis extend- ing, from around the valve ring into one coronary artery, in vit. of adequate anticoagulant therapy. The use of thcse prostheses in ohildxen is even mono preblematical. In addition to ell the above mentioned disadvantages, the prosthesis has — 37 - to be small to fit the small aortic r the child. That the pros• thetio orifice maybe inadequate for the same person few yore later is self evident. fleet workers prefer to postpone the valve replacement re long as possible in Children with aortic velve disease. Graft surgery of the aortic valve seems to be a more re onal approach to the problem* Xt offers a valve that is neatly identical with the natural one. it is superior from the krirsulic and mechanical standpoints, to the caged bell valve. It may even grow with the aortic ring, though no evidence on this point is available yet ticoagglants have not becu found necessary in the postoperative period (Barrat-toyes et el, 1965). Of the various grafting materials, ze«dried homografts are the frequently used Large scale use of tt>is procedure is impracticable because of limited supply of suitable valves ona because of the difficult technique. Proper matching of else and conflagration of oacoath graft to the aortic ring maybe difficult. Tailoring= artificial valve from the patient's oesen times (e.g. or Paola iota) is another logical epproach The ccometric rules necessary for making a tricuspid valve from a flat piece or tissue are now Moan (Sewing, 1965). The grafting tissue is always available in sufficient quantity and there are no iffrimologicel prollems. ramie late seems to 1,e superior to pericardium as a crafting material* and is more abundant (;?,enning, 1965). ftperienee pith the use or the fa2cia late aft to too small, nna postoperative follow-up is too abort for adequate judgement. 38

It ie unlikely that the use .of heterolo s aortic valve te. will be of percinnent value as the immunological proble ie are, too t. SWIG j Sif Tirptiap VALVE Teo affections of the tricuspid vale call for surgical replecementst rheumatic tricuspid inoomp tence and stenoais and Ebstelles anomaly. In the case at rhealmetio tricuspid incompetence oonsiderable stutly clinical experience convinced neny 'porkers of the futility of' valvuloplasty for tricuspid lesions. Cicatricia scarring and retraction of the tricuspid leaflets appear to preclude satisfactary,plastie procedures in most cases wIth tricuspid incompetence (Miehei et al. 1966). tostheticacement the valve has been ettamptmi In oon,3unotion with mitral valve surgery. Lillehei et .1 (1966) reported euocessful replacement of the tricuspid valve with otarr-Dleards prostheses in 6 patients. All the patients had a mitral oomminsurotopy or replacement at the name time. Starr et al (1965) reported 19 tricuipid valve replacement prooedures: )4 with a single stage triple (tricuspid, sertie and mural) valve mit:cement, one with two-etagee triple replacement, and 4 with nitrel and tricuspid replacement. Sixteen of the patients sur- vived operation. There were no complications due to tricuspid replacement. /n Mateinos ennitol,y, plattio pro:mauves were performed on the displroed tricuspid valve by ITurter. and Lillehei (1958); and Bahne04 (1965). Nernard and Sohrire (1963) reForte6 the first excision and replacement at' the tricuspid valve in Ebsteines anomaly uaing a lenticular - 39 - prosthesis with a ()antral =speeding shaft (see men Cartwright et al (1960 reported dramatic improvement following the same procedure bUt using, insteadil the Smelofr4utter coucLustop..- Tee protedures seem to be ea t of advanced valvular disease of the t. So far, annuloplasty is suocessful only in a. limited number of carefully damn eases in whom the main: pathology ie simple anPoer dilctation

without gross deformity of the valve apparatus aib cases require total replaoement of the valve. Home. and cut aft replace. meet of the valve are at the present time succesef01 wily for the aortic valve. Owiue to the complicated anatomy of the mitral valve apparatus it ean:.tonly be replaped by a proat%aMs. The use ar these natural grmrts is limited, even in the aortic ar4, by the difficulty in Obtaining and handling the graft rid by the groat 41411 reauired in its gement. Thuii'most caeee of aortic replacement and all oases ormitral replaces. meat will continuo to beiiirfOrmed for many ors to come with prefab.• rioeted:proetheees. in view Of this • it mama important to review in detail #tea rules underlying the design and manUfacitUre of)roatheses for both aortic) and mitrel valves; with particular striae on the latter. te the essential function of a prosthetic valve is to allow adequate volume of blood to pass through-it easily in one direetion• an understanding of the physical principles of blood fles'ia important in the deaign and. shall be outlined

in Chapter III. As the prosthetic valve must be fitted in the cardiac trioular or aortic writ the enatogy or the heart chambers also be di eettesello COITSIDEkTIOTiS IN FR YAW

Several hydraulic principles are relevant to valve desk. ire artificial valve is required to allow the flow of a varisMAr volume of blood in one directions with a 041,13ffel pressure head and very little or no turbulence Several Outlast laws govern the flow or fluids in general end their flow through orifioes isparticular. These moat be tdken Into consideration during the design of any valve. the factors favouring the comment* or turbulence need to be biotin in order to be avoided. The ctatio end kinetic forces.that may be applied to the various parts or the valve during the phases of the cardiac crate owes be predicted. The exact megaitude of these form le important in order that en cppropriate material for the valve can be Ohosen• ?lint Mil

There ere two basic 013 eat (pito 1 ).

In laminar flow the fluid nevea in parallel as (summate. Men a fluid to flowing past a surfaces there exists a layer of fluid adjacent to the surface through which the variation of texas? between the fluid and the surftce is transmitted. This layer is Imo en the noundary layer, and the whole of the V1300113 or frictional realst.• once between the fluid and the suedes mourn in this layer. The layer no be imagined to consist of a Ember of thin parallel streenhands each

-4 0 c- , A7‘..\rif d 41,41, yo 47)4. at yid 14 t4kiii, ,ziGirt ••• z p 1,7,‘ 4t.vritie4 /;;;41-1,

STREAMLINED FLOW (a) TURBULENT FLOW (b) Fig. 1 Shows the stream lines of laminar flow (a) and the cross currents of turbulent flow (b)

Streamlined Turbulent Flow ; Flow

Fig. 2 DRIVING PRESSURE

Flow-pressure relationship during laminar and turbulent flow. having a slightly ger velocity than its inner neighbour. The band immediately adjaoant to the surface adheres to the surface sal has no velocity.Working outvote from the surface, the next band has en extremely email velocity; each eucceesive bond berm/ will have a slightly higher velocity than its inner neighbours until, finally a band 113 reached which has apprverimately the full velocity of the fluid. This last band in the outside of the boundary layer; no further fluid resistanos is Ireneraitted to the surface beyond this outer limit. The twoning holds it a body is moving in a stationery fluid. 7Cr flow in a circular pipe, the maximum velocity is twice the average velveui.ty. Turbulent tzar is a sr ^ecterissed by pulsator; crostwourrent velocities; eddies, and vortices. of the cross-eurrent velooittea of

turbulent flow is the formation of a more =irons velocity distribution. For turbulent floe the maims velocity is more of the order of 1425 the average veto:lily. The more uniform velocity found in turbulent fzow brought about by the inter.change of mormntue between fast moving particles near the centre and slower ones nearer the galls One of the most important practicel differences between laminar

turbulent flow is the muoh greater Oftergy loss in turbulent flow. kinetic energy which is required to produce the orose-ourront weeloci. and eddies must be supplied by the pump (e.g. the heart) but is of alp in transporting the fluid through the pipe (e.g. the blood vessels). t of turbulence may significantly reduce the delivery normally ved by a given pressure and a new law replaces Foiaeulles low (Fig, 2 ). The resistance to flow now depends on the density of the fluid rather than an The viscosity, sines. larattic ene &mit/ velocity (Tlurton. 1960). maelds*. Nipbert. Weems forces lend to hold the laminas in their relative positions, i.e. the ewe viscous the fluid, the less likely. 'is the °maven*. or turbulence is it. The likelihood of occurrence of :turbulent* increases with the increase of the • radius of the tube, the veloed.ty of 'flew and the density of the null. These *relationships leading to • osournaes of turbulent*, at a critical moment wlsre described by Remolds (1883) and are given by. Reynolde* waiter (R). Reynolds* Meter m peasttr j eltworAnadius Viscosity Turbulence is likely to occur whenReynolds* Nutter is 2000, or more. l*FF, OF MARS IV The tern *tube* is applied to a fluid pathway at which is sir tines creator then the diameter, (Rat e& et al 1963 The amount of flow of a liquid in teebee (9 is governed by the pressure head (P), visoosity of the fluid (u), the radius and length (L) of the tube. The relationehi beteeen all these footers is given by Ilagen.foiesuillels Law (839 • eO) s QmPrifr acz14 at Tr u It will be noted that the pressure head and flow Cory .th the fourth power of the' radius of the tube (II). Ilaten-Poiseuillets Iew applies only to laminar flow of fluids novella . (Newtonian) viscosity. In the human body the fluid is blood. 45

This has ous viscosity, so the visoosity factor is not ocmatent. However, it turns out that this is not a serious factor in the range of phyttiologioal blood flows (Burton, 1959). !mother oomplication in the case of the blood weasels is their distensibility, i.e. the radius varies 'frith the change of internal pressure. A third caplication is that blood flow in many parte of the is turbulent, not iervilivir. MY o Et•uX WAIT* is to a fluid psthwey of is h the greater the diameter compared to the e ppm& the ideal orifice (ItoIntooh al, 1963).

The flow fluid throe, an al pmt, avd

Ince the particles are jostled ab is considerable loss of eneriw and therefore of pressure. AS soon the flow becomes turbultat, the density of the fluid rather ts Plays the important part is determining the volume fl t al, 1963). Ciirtiffialik Or ca4V$04 4'Plz VP, 1131,4 00161 If an orifice has a sharp edge, the stream lines set up is the approach the orifice in ell directierus (F1.3.3 ), and the direction of flow of the particles of liquid, except very near the centre te not nom. to the plansof the orifice but oontrierging to produce a contracticm of the jet (11/11, 1940« .A.t a. small distance from the orifice, the stream linee become prao.. telly pr3rellel but the cross sectional area of the jet is considerably Fig. 3 The contraction of fluid jet after leaving the sharp edged orifice.

U Sharp edged orifice

Orifice with well rounded entry

Short Pipe

Short re-entrant mouthpiece

Long re-entrant mouthpiece

Divergent orifice Fig. 4. Types of orifices (Rao, 1962) 41

less than the area of the orifice. If al is the area of the jet at this section and a is the area of the orifice, then the ratio L is called the a Coefficient of Contraction and may be denoted by CO. For a circular orifice with sharp edges CO has a value of 0.62 (Rao, 1962). Velocity of Flow ThrouGh an 9rAficiss The theoretical velocity of flow v through any point at an orifice is proportional to the pressure head above this point Of the Prince i.e. 0N2g P, _mid g = acceleration of gravity P = Pressure head Coefficient of Velocity.for,a t9sarojilged Orifioes The theoretical velocity w fors, sharp edged orifiee was show to be = 2g P but the actual velocity wl is elightly less than this due to friction at the orifice. The ratio 71 which is celled Coefficient of Velocity

cw = Yi vl * cifir•P

pvantity of Flew inn a Share Mel Orificek TO CoefrApipat of Discharge: The quantity of discharge per second from an orifice (Q) is clearly the area of the jet at the contracted section multiplied by the mean velocity through this section and is therefore: = Co • Co • a 0V2g • P

Aga Q = flow through the orifice C = Coefficient of contraotion Cv = Coefficient of velooity cz area of the orifice g acceleration of gravity P = pressure head 2g.15 theoretical ve1ooity of the jet.

one value for C call it C i.e.' c c fiteient of

Q=C• 2g•P of the orifice OMbt tbt same

The values Co CT and. C for different type s of or a is given in ile2 (mss 1962).. (Ifig•4

GORLIN TOW/MA Goat% eM C (1951) equation, in reining the areas of the gli pr valves as 'ell as septa defects; rifirm re*Tir- 6 = 980 4023/••000. airiro 445 *• 6 4•5 stP Ana a = aro*. or the valve Q = valve flow is adiese P = pressure gradient across the valve C .= constant of discharge. to be derived everimentally• - 49

co C v

0.62 0•98 0.60 0.99 0.98 0.98

Short pipe, lllo 1..(X) 0.82 0.82 mouth-sue n.-surest mouthftpiooe (alert) 0.55 0.98 0.53 Re.entreat netith-piese (1 $) 0.72 0.98 0.7i Divergent (flared) winos 0.99 0.98 0.98 - 50 -

P oarz to obtained by oatheterisation• feline Corlin vrAd Carlin during operation on the aot valve (or Tern). Thar then derived the value for C which vac 0,7 for the ve end 1.0 for the aortic valve* So the

in formula used clinic alkv 1st e mitre valve a = 4415 *VP

ARTIFICIAL VALVES t The flew fluid (e.g. blood) across en artificial valve is governed by the same law i.e. Q sr C • a 428 P. In doing the eff'icieeco• 'ef the valve, values for C end a are required. C could be calculated if tbe effective valve area is known The efrectifre valve area in prosthetic valves *doh contain an obstacle in the mid.streata, e.g• caged valves, lenticular prostheses, and discoid prostheses, is evidently eamller than the actual area of the orifice (norm et al, 19641 Kesedi et al, 33%), So, *0 or of be determined simPitY by plazdentry of the valve orifice* roitcNk Aorrx qp man= wimp As blood flown through the valve a certain unt of force is applied by the flowing stream on its meohar,sme A knowledge of the magnitude of this force is of peat importance in defining the neoessary design and streegth of the oonnection needed to keep the mechanism in pleso• Calculation or this force is more important in the design of the aortic valve then in the mitrel valve, because much 51 larger forces are oppliod on the aortic vel during ejection. Tluid•Preksuro op a rlibmeriecl Bodzis (Lees,',1948) - • • • • '• • The force applied by, the •fluid- stream on a •body suspeinded, at'a•• riet•ingle to the direction of theth flewfl is a simmation•of the stutio pressure of the fluid ct•thiellipth plus . the kinetic energy. (4E.) at the flow and is .ven by the lia.rnotali. equations , . V = A • + dv2) tat P = force applied on the mil:merged body P, :3: the. etatic pressure. (o•g• like that aeured from the ' side hole of a catheter a = aproity. of fluid v velocity or flow (equal to N2g• Pressure gradisnt) It= "ea Or the adsorged body (0.8• valve trapadoor)• "?,ais equation gives the force applied on thedisc of e.g. Hufnagel valve which is at a right anee to the strews of blood flow when placed in either the aortic or mitral areas• If the valve mechanism submits asvanglo on the plane of the flow atream more 0r leas than 90° e.g. as in the cane of the Hemmerandth valve and the laillehei vats, then the force applied on the trap-door tiU bet P = A • (F. + dv2) • alai) lust 6 a the Mao between the trap-door and the axis of flu A area of the trap-door

Prt Rpticn p Pikosprac VATVZi• Pluitl flow around streamline objects does not result in turbulenee. If flow occurs around a blunt object. e•g• the boll of the caged ball valve, a broad, eddying eeke forma downstream (Fig. 5 ). Because or the blookeee of the main floe due to the space 000upied by the wing gave the flow patterns and with it the pressure distribution is disturbed. The pressure in the rearward part of the body is lower than in the format part due to los3 of eaerg7 moondary to turbulence and crossuiourrent velocities, This reeults in a net pressuro dreg the body away In the doinstremee

If a streamlined object is placed et an o ( 6)

the traps door of the Heamersmith vave, turd on the side of tha valve awey from the current. a this side

be lower than the pressure on the side facing Ire, 1961). -3CPAR: Several rules for the designs and evaluation or an valve combo conoluded from the above review: (1) The of feotive orifice of e.vulve is al. ya smaller than the aetual oritioe by a factor equal to the oce 'Y'icient of dies or tads CO. (2) The hydraulic performs as or o f icescon be opt. by ing their coefficients of discharge. best perfornme is achieved by roundwedged orifices (C Me). (3) A certain degree of turbulence is &moat invariable distal valve seachaniem which is placed in the middle of the flow stream. Censequently the natural valves as veil as the leaflet and sleeve valve designs are far 1eap likely to produoe turbulence than any design containing - 53 -

PATTERN OF FLOW AROUND A STATIONARY ROUNDED OBJECT.

Fig. 5

PATTERN OF FLOW AROUND AN OBLIQUE STATIONARY LENTICULAR OBJECT.

Fig. 6 or lentioular neelmniam, roe is enhanced b the increase ill

More turbulence thus produced in the sortie then in areas. The design of an aortic prosthesis calls ftr more earn in ATOiding factors that may ed to textulenoe than a desigi for a mites. prosthesis. (5) lie forces applied on the valve are ,a oombination of static pressure in the omits* @lumbers and thy Icinetio energy of flow. This kinetic energy is proportional to half the square of the flow welocity• The terms applied to an aortic prosthesis ere thus much more, than those applied to the mitre prosthesis.

(6) The floe through the valve is not afros:tee tsy in viscosity of fluid; thus the valve can be tested in a medium of rater stead .of blood without affecting results of the Usti. — 55 -

aIAPUlt rV

ONICA C0,1117PF.RATIOT , AWE D ciI VP

Proper underst anding of the detailed ens the ,17t »ear aparatus of the human heart and the related strutrturesi.a imptertent for several reasons. The prosthetic valve ring must be designed so as to fit snugly in the cardiac skeleton and boo= en integral part of it, causing minimal or no alteration in its =at m,. The design of a preathetic Valve raeohaniem must take into consideration the spas* available in the ventricle or aorta amine Arstoie exd diastole and the amount of t pecmitted twat be related to the length d disaster or the left ventricular cavity. The pr oathetio Valve orifice must be in lire with the normal inflow pathway of blood. As far as poneible the valve must not obstruct the left ventricular outflow path.. way during ejection. A knowledge of the important structures lying in relation to the valve annuli is eseential for the surgeon performing the valve replaoement in order to avoid Injury of any important structure during suturing.

'FM CAC tae cardiac skeleton is mainly oomposed of two pairs of fibrous rings s a pair of venous annuli that serve to separate the atria from the ventricles, and a pair of arterial annuli separating the Great arterial trunks from the ventricles (rig. 7 ), The farmer fort an almost complete partition of noromuscular time encircling the waist -56-

PULMONARY LEFT ARTERY --ATRIUM AORTA--- RIGHT ATRIUM---- eft'. '01

FIBROUS SKELETON-=

AORTIC vAt..vq PULMONARY TRICUSPID --6VALVE. VALVE,

Of"' MITRAL 1/7 VALVE RIGHT LEFT VENTRICLE ( /// //q1 --VENTRICLE

Fig. 7

The components of the human heart (from Rushmer, 1961)

U. 57

of the, heart and ova:wetting the atrie3 from the ventricles s it thus only physiological connection between the atria and the ventricles ie the atria t iculnr conducting. bundle. The cardiao museulature and eortio oonal outlet:: is separated frau the smooth muscle con d in the walls of their respective arterial trunks by fibrous rings making the trunco-oonal Junction (Ideate, 1959). In addition to these anandii the skeleton maiden condemnation brow, tissue between mitral end lalicuapid valve ri called the brous triton° and it also inoludes the mewnbraneous part of the ventricular septum. The cardiac skeleton gives origin and insertion all cardiac musoulatvre. The general description of the anatomy the various oomponents of this skeleton will now be given. ii‘SyKliii/ICULArt The JAW and tricuspid valve rings arise frae o triton°. atrio.ventricular annuli lie nearly in the sagit p th the atria towards the right and the ventricles towerds the left 7)• The 14.traliAnnuluqs The annulus of the mite eve ls b into parts for descriptive purpones: the antercoimedial onc-►thirod and the ataro.- lateral two thirds (Davila, 1961). (a) The Antero•oldital gie.thirat Thin is the fibrous tri, r of the cardiac skeleton. The base of the anterior leaflet of the mitral valve is attached along this part to the annulus. The relation of this leaflet with the non-coronary cusp and the left coronary cusp of the aortic valve is surgically isoortant. 58

The two aortic °tape aro attached at their bailee to the aorticannulus eh in this region is interlaced with the nitral =Lulus, the bases the anterior mitral leaflet the root of the aorta and the left etriel myocardium (Davila, 1941) (b) Pemainina rite-tlyirdea The remaining two.thirds of the a=lulus le not a well-d a tomicel struettav„ being about the eisa of a pieoe of heavy suture material.:The base of the posterior leaflet is attached to the endscarSal side of the annulus.

The "1104514-9. acs tricuspid •annul= also arisesthe fibrous trigone. As the name implies, it gives rise to three i.caf ets, i.e. anterior, medial ni posterior leaflets anterior leaflet arises from the etcrnvooctal soffitthe e nrsulus. In this region the anuelus is reinforoed inferiorly by the pariethl band of the orista illipraventrioularis. Tile anterior leaflet forms a well•devoloped modbrane that part:3.011y partitions the ventricular =wit/ in a fashion etimilar to its counterpart in the left; cavity. The chorine tendineae sowing to anchor the leaflet in position arise mostl,y from the anterior papillary mimic. Me base of the medial cusp takes its origin from a line or attach. ment rhioh is directly related to the Eleenbreneouo The precise line of attachment of the valve to the fibroua septum is exceedingly variable. It lies at a level come chat lover than the attachment of the anterior cusp cr the mitre." valve. Meet of the chordate teedinoae - 59 -

csh.oring the medial amp arises from tho eeptal papillary e• , anterior and medial leaflete form an archway so that the venous turn muat curve in order to enter the outflow portion or tho right trials*

The poeterier leaflet leas etrongly cloveloped the ther tsar eefl.eta and arlecs fram that part,,or the annulus t to the atrial floor. The hordes tendialeae hox le normally arise from a number of timpll papillary mus situated along the ventricular floor* ltt addition to the three ma.in leaflets desczolbods ernumerary Lem at;a occur frequently :at The inter-valvular spa F

tee 8.

Both i.t tricuspid annuli are terior3y to the

valve, aria the bundle of Ilis lie between the two cumuli, Ex Y• tricuepid valve cumulus ie related to the right coronary artery; witral annulus is, related to the circumflex coronary artery. the treat cardiac vein at the coronary sinus. te r, Teo such otions mists one at the emmancement aorta from the left ventricle; and the other at the level of cement of the pulmonary trunk from the menus of the.right ventricle* agiblia=rimanistall Below the level of Ike) mama:47 valve, Vie canal us . very thin as it lion against the aorta, In arose section the well of the con= -60-

Pulmonary Annulus Aortic Annulus

Right Coronary Artery

Left Coronary Artery Tricuspid Annulus Left Fibrous Right Fibrous Trigone Trigone Mitral Annulus Bundle of His Great Cardiac Vein Coronary Sinus Venous channels Mitral Valve Arterial channels Cardiac Skeleton Heart muscle Fig. 8

The relations of the cardiac valves and the fibrous skeleton of the heart has a crescentic oonfi tion with its thin segment farming the fl oor of the infundibultas while its more musoular Dement forme the free well lying anteriorly. Slip: of may bo found extending wards for some distance to pass into the adventitia of the tau* Meat% 1959). The lortiq trziaus end Valyet The three aortic valve leaflets in effect supported between two fibrous rings (Cross et al, 190.) (Pig. 9 The first end most important is the true fibrous annulus at the base of the aorta. The second ring is above this at the upper limit of the sinuses of alva =I is formed by a s1id3 thickening in the aortic we3.1. The upper rentefus has, diameter which is slightly smeller then the lover The lower tumulus is the atronger st imcturo and has three fibrous struts projecting upwards 4ch terminate at the upper ring. Met rgfts of the valve leaflets are attached to the lower l inns and its projecting 'struts. The free edge of each lea.flet is suspended from the upper

annulus in such a way that the centre point of closure of the leaflets during diastole is at a point one-third of the evere.13. height of the valve. This results in a basket or sling effect by means of thich the forces applied. to the cusp by the aortic pressure head during diastole are distributed tos and. absorbed by, the fibrous struts at the ccateissures and by the upper aortic rin. Each cusp is shaped like a e1ight1y flattened sphere, the diameter of which is about three-qua. tars of the diameter of the aorta at the annulus. liva cajor cir ar mce of the cusps in below the lip of leaflet so tha y the circumference at tba r ergn is cliche:7 restricted

-62.

Wall of Aorta Upper Ring

Struts

446 is"• Sinuses of Valsalva Lower Ring Aortic Valve Cusps Fig. 9 The structure of the aorta-a—Wave and the root of the aorta (From Cross et al, 1961)

c.

A. 1. Left atrium D. 2. Aorta 3. Right ventricle 4.. Left ventricle 5. a.

F iK. 10

The plane of the mitral and aortic valves in normal heart (A), mitral .stenosis (B), left ventricular hypertrophy (C) and left ventricular dilatation (D) (From Grant, 1953) - 63 -

This gives a ballooning effect that allows each leaflet to cent itself an the nei&houring lea/lets hen the valve le closed (Cross et el, 1961). The leaflets sac below the level of the annulus giving a smoothly roundel base to the cusps. The nodules at the centre of the free edge or ozob leaflet (the noduli arr til) funotion to Goal the residual tee ar opening at the point of apposition of this three leaflo tu. Below the level of the upper aortio ring, the aortic wall thins d expands outs ards to form the sinuses of lre3.telva which terminate below, at the level of, the true aortic annulus. This expansion at the base of the aorta forms what is essentially a spherical chamber within %hi& the aortic valve leaflets function. During eystole the valve leafiete do not becoae flattened against the sinus pail as they Mould if the aorta were a aimplo cylinder. They awing into a neutral position about mida hetet) the centre point of the =lulus and the wall of the aortic sinus. The leaflets retract partially by elastic raced and Partially by Gentle Maine« Me wall oft anuses of Valealva bumi.ges cutlasses well 'beyond the Unita or the aortic annulus, A richt entarior dilatation projects into the thin veiled Initnaibulua rhoroce a poi:LW/tor dilatation cratonda bac% over the intor..ventricular septum and touches the medial w.11 of ridit etrit=. A left =tett daatation is directed agninfit the . n structums around the cortio valve cD well as the position of its corrissures and the pita o'2 origin of coronary arteries is °horn inFig.

e.tto.n 'heft aortic valve is

ort t. Of the first 16 aortic valve ropleo cents pa car by el (1%5) Z. had chronic complete heart block postaperatively, further investigation, those corker found closo rolati hip town the ,adjecont portions of the itte%t and peaterior (nonwocronari) op of the aortic valve on one; 1.1.1nd end the hula° or Fais'on the other, Sri TRTG9ir

The fibrous trigene, lies obit between the atriaaortic teal

triourpid valves (rs.c. 8 )6 tnter it ilea in relation to the circumflex branch of the left ooronary artery and tet'the great cardiac vein. Posterlorkv„ It calends to the region where, the :middle Cardiac vein beoomom the coronary 'sinus at the junction Of the interatrial same, posterior longitudinal =lout) and the atztomventimieulor grooves' sRw right fibrous trig= lies po te3,ocedially between' the mitral and' tab:cuspid valves encl is the thickest and the strongest part. The left fibrous trigons lies between the left minus of Valcalve and the. anterior leaflet of the mitre/ valve. LTRASIN pyo OP Tip-7 u 1,PiLVE: CalriCES AM AMUR: (1) ?arm. vgVTI Rusted (1952) estimated the circumference of the ate rralve rind as 7•5 .104 ems in the female and 86 —11,0 en. in the ce e, 110 found, that the, intorea=issural diameter to 1.5 300 ens in the female

and 1,9 307 on. in the males The width of the oomMissuren'were, according to the came author, 447 0.8 ems The area of the normal - 05 -

c1 ire orifice is .0 3CI•

(2) yr,I;vgs =Lulus ha s a circumference of 114 1960). This mesas that the annas, diameter the annular area. is 11,5 13•0 aq o MVP,:

:The eircumeercnco of pulmonary valve bus is 7.0 as.

1164;1.• 4.92l). This suns that the iwriuler diameter 54 2.2 and the area of the pulmonary annulus is 3.9 sq. as, VALV: twain (1929) estimated the cross sectional area of the as about 5.3 sq• cm. Due to the =atm, of the the sic valve orifice is triangular* M.tlaix (1955) est tothe of the tricuspid aortic orifice as 2.6 3.5 sq• tra. IS OP 1,1=';1, vAirlppyps,pstBrxqp ,7 itra virriaCtlitAR crarr

The plane end spatial reiat'3.on bip of the ratral va3v rY importaatin prosthetic aesisn 33 they deter:Line the direction of the lie or the prosthetic trap..door,. octge or leaflet in the' left ventricular cavity, whether it mill obstruct the pathway of Wootton and *ether it can interfere ulAh ventricular ace:traction.' If the long axis of the prosthetic lacchenirm is parallel to the lent axis or the left vent.. ricles it trill offer los obstructlen'to the blood flowana rtill be less Likely to interfere with loft irontricular contnactian than if it is at a right angle to the long axis of the ventriouler weir. - 66 -

It must be borne in mind that although the left ventricle is dilated or hypertrophied (or both) at the time of prosthetic replcoement due to valvular dysfunction, yeto after replacement it gr2dually shrinkm to normal else. The prosthesis must be aAnpted not only the spe 03trrnsienn of loft ventricular cavity at the time of operation, but also to the chan;2..e, in ventricular sine and shape expected to develop in the immodiato late pootoperative po The plane the mitre/ valve is mar right angle to that of theoortto Tel e. grant (1953) studied the position of the mitral valve in normol heartno in mitral stenosin, in left ventricular per- trophy,y, and in loft ventricular dilatation (1i .10 ). fie found that in hearts with mitral stenosin„ the 'Tatra ring is tilted so as to cone more in lino with the lonc axis of the left ventricle and ao making a more acute nc1e with the plane of the aortic valve. The reverse occurs in eases with loft ventricularhypertrephy. In this condition, the plane of the mitral vslvo is tilted BO 00 to maks it more nearly parallel with the plane of thoacrtic valve. The difference can occasionally be seen fluorosoopically when the valve is calcrif led. In left ventricular dilatation (a .c. in oases with mitral or aortic incompetence) the plane of the mitral valve is tho same as in the normal hearts. In thin study trtvince were made of the left ventricular cavity silhouette from the lateral view of onglocerdlograms in patients with mitral atenosis, left ventricular hypertrophy, cud left ventricular dilatation. These tracin,s confirm the earlier concluoions made by Grant (Fig. u ).

I'brIt by Davila rr his colleagues (1961) :bowed that during systole, - 67 -

M• C - M.S.

H•F• H•0•C•M•

J•F•

Fig. 11 the relation between the plane of the mitrel and aortic valves and the long axis of the left ventricular cavity (LV) in mitral stenosis (MS) hypertrophic obstructive cardiomyopathy (HOCM) and in mitral incompetence with left ventricular dilatation (MI) the normal left ventricle &sauteed the aape or a r 12) with the core° valve at one candor the cylinder. una the oloscasmilaeal valve (the anterior aflet) acting like a curtain window at ore vides

While the ri ventricular blood flow is unl ctional 018.13) in the left ventricleit in bidirectional. So. While in the right' ventricle the blood enters at oao orifioe and leaves at another, in the left ventricle blood enters ana leaves fram almost the'sene orifioe, which is divided into parts the anterior, leaflet of the mitral valve (Greet. 19G2). Stood flows in on one side of this Curtain ana out on the othor side. This partition is ri red with the ezoiaioia of the mitral valve prior to ropaacement and tae beim and the outflow tracts become osaentially ono confluent pools This means that the ideal deeiga far the new mitral prosthesie must incorporate a IMMO of directing the blood towards the aortic valve. The inflow and outflow orifices of the right rrentriele. separated by musculature. This is the crista supraventricularis. CoyCLIXION: This review shoos that the left ventricular cavity the chape of a cylinder during contraction and that the plane of .04 zaitial velvo annulus Jo =ore or less parallel with the long axis of this czeurdor.-. The dooign of a valve prosthesis with a rigid meohanism calls for careful coneideration of these anatomical feats, Thus a mechanism will be bettor suited to the anatauy if it3 long axis is parallel with the loug axis of the ventricle. i.e. parallel with its -69-

Aortic Valve Struts Aortic Annulus

Anterior Leaflet of Mitral Valve

Fig. 12

Left ventricular cavity during early systole (Davila, 1961)

FLOW PATHWAYS FLOW PATHWAYS: IN THE IN THE LEFT VENTRICLE RIGHT ANO LEFT VENTRICLES (Lateral view ) (Antero-posterior view) ovn valvering. In the aortic area, the long axis of the flor pathvay is perpans dicular to the plane of the valve annulus. Amami= for an. crtifioici aortic vulva will be more suitable if its long exis is parallel pith the long axle or the aorta, i.e. porpeadioularto its one ring. Ths area of the aortic root vas shorn to be 5.3 cm 4. The vmkhanism of sql prosthotiovalve rill occupy part of this area. it must be small in order to leave enough spaoe around it to allow the passage of blood.

In choosing a mater .a1 for the ae pro the

valve, several factors must be taken int t conai teria3. must be bioloGically and oally inert It must not induce throiaboeis or allot ttmotbue to *recd. over ts surface. It must not excite excessive foreign body reaction or haemelys e. It must be easily =nide& pod easy to sterilise by thermal or chemical means. Another important consideration is the ability of the valve to tithstand the repetitive mechanical insults it Maven during olvninS

and closing. At pealt ventricular pressure, the let s the normal titrel valve as'a thole is subjected to tIvz equivalent of 2 pounds4quare inch,. in normal human adults (Davila, 1961) because: 3.20 ma i!g, = 156 ort/cu 093.56 gra/ins2 a 1,95 lb/ins The pressure load can reach up to mare than double this value tith high ventricular systolic pressures (e.g. tith aortic stenosis or systemic hypertension). This force is distributed over the entire area of the valve but is borne in the last analysis by the structures which support or restrain the leaflets, i.e. the chord= tend/nese, Ito assmmo that the leaflet area is 1 ins2 (101e. 5.76 am ) and that the cum of the cross sectional areas at the points of chordal attachment is 0.1 =2, - 7 than agreed distributed among the. sites of chordal attachment is normally 2 lb/0.1 cm2 or 20 lb/an rtbieh oguala 215.2 p square inch.. 2irithor. . caloulz#043 mu3t bo oarriOa out for on.Y.Prceopod valve design and the force Lich the valve must bear should be =pared rith the known tensile and impact strength. of the materials. Leaflet or sleeve valves are subjected to another type 'of etressa s, namely folding, at ratan varying. from 60/minute or leas, to 160As3nuto or core. The rketer-ltucle of this atrees will be recognised if ie remember that at a rate of 70/minute, the t>esurt boats about 36,288,000 times per year. It is thusY important to know the main physical, chemical arml biological props:it:Lea of differmit suitable materials and the methods available for their evaluation. yountss A•polymer iz a large molecule built up by the repetition of smal simple chemical units. In cam cases the repetition is linear, i.e. aa a ohen. In other oaso the chef= ane'branohed or inter-oonn to form a throe dimensional network. The length of the polymer -chain is specified by the numbotr c repeat units in the chain. This in .called the mgr of Po3,grusrisation. The molecular relight of a polymer is the produot or the molecular idst of the repeat unit (monomer) cad the de a of pAymerisatton. The decree of ,0 -arisation b determined by purely random events, end meg roach several thousand or more. The polymeric product oontftins molecules having different chain lengths. Since the distribution -?3 -

of molecular weightexists in any finit sample of polymers the erserisy mental mecsurement of molecular weight can give only an average value. F;CTORS tw.EXIXRIZaPISICAL PROMTM 0_ POIXVERS: / auwalaatia= As the molecular voight increases, the physical state cr the com- pound change from E s to liquid to solid, ea happens, for example, in the cenufacturo of polyethylene from ethylene (Carside and Fhyllips,

1962). Crystallinity depends partly on molecular weight. The leas the molecular reidit, the higher the crystallinity becomes. ttlt viccosity cnd impact strength aro directly proportional to the molecular weight. 2 - Crystallinity: The major factor determinin whether a polymer can crystallize is the occurrence of euccessIve units in fete chain in a configuration of geometrical regularity. iiatta (1955) discovered a technique by which it is possible to synthetical a Otero-re compound with a special pattern of arrangement of atoms and molecules, rift hence control crystallinity. Ctiffness„ tono5.10 strength and eoftoning point are all increased with on increcsinc decree of crystallinity. relationship between crystallinity? moleoular weight anl physical proportlos car' any polymer is shown phically in Pig. 14 (Billmoyer, 1962 A • 21121414C 1-MitILMUSZZaL The. phyacal chnracteristics of polynora can be discussed under

the following headince: Propertieot The definition of the differentmechani properties of polymera which are of importance for a synthetics valve and the methods of their evaluation am es follows: (i) Stress-,trqin Prp: tiess Men a tensile (pulling) stress d (i.e. stretched). At first, the strain will be proportional stress (Hooke's Law). then the elastic limita or the materiel are exceeded, sudden increase in the rate of strain occurs without further increase in stress (Fig. 1 point at which this occurs is called the Yield Point. If the continued (or increased) furhter stretching of the material occurs rapidly until it breaks Both tho stress necessary to produce sudden elongation of the material (Yield Stress) and that necessary to break it (Tensile Strength) are used as criteria of the material's elasticity en trexigth. Adequate tensile strength is of utmost importance to all rosthet-_ los used in the vascular system an] the boort It is also important for the suture material According DeBekey et al (1965), tie en« casement of the suture lino in collagen and fibrOblaate derived from the host is never sufficien4y strong to rithatand the continuing pulsatile thrust in the heart. The strength of attachment will. depend, according to these authors, almost entirely upon the continued strength of the prosthesis and its suture lines. It is important to realize that several materials lose part of their tensile strength after implantation for a period of time. Typical of these are Ivalon, silk and pylon

-75-

z HARD HARD 2 BRITTLE STRONG —J NON- POLYMER — SOFT 13( HARD 8, cr WAXY BRITTLE U 0

1000 1000-10,000 10,000

Fig. 1k MOLECULAR WEIGHT

The relation between the molecular weight, and crystallinity and the properties of polymeric substances

(From Billmeyer, 1962)

Elongation at Break

Ultimate

Yeild Strength Stress

V Fig. 15 STRAIN The theoretical stress-strain curve for polymers -76..

(Deekey at al, 1965; Timm and Essig, 2959; Harrison, 1958). Denalsay of ci (1965) have seen a number .ef patients tith lmks through sutures several yearn after implantation of vascular t3e These workers favour the use of p1antic suture materiel of sisuilo composition to tileprosthetic material used in the construetion of the artificia' valve. (2) • This if, the abilit, or thasUbstance to resist impact e,o, the impact of the trep.dcor on the ring of the Hammerstaitialmlve, It is comic •meestmed - by calculating the amount of energy required to cause a break in material tested* (3) Hardness: This is composite propert, coabinin 'concepts of resistance penetration, corate!zinc, marring- otos The majority of hardness tests are bated on rosintcncc to penetration by an indentor paszed into the plastic unbor a constant load. CL 3 .Tear Resietoancot This .s an important chareeterintic in the leaflet valves and•in prosthetic cusps. It is estimated by r asuring do force needed to ocatinue a tear that has•alreaki started in a. material, (5) rolgin? F ranee: This is also important in leaflet valves anti in prosthetic cusps. It is tested 1:y the number of times the mater4^ 11s to be- folded lefore i;rasang. -77-

Mena 1,roDe p (1) Vt9WW! Tomileratues This is tho tenporature at uhloh the materiel starts to become plastio in ebaractor. rouldinc or tho valve can only be reLthinc this tenvorataro.

(2) 1.42447-1) 11140 .Ais also is desirablo9 otherniso, chemical ste-ilisation 1111/ be essential. /II - quercalroportiest (1) rloot%ricast Some materiels r vo a nsturelly cc athor surraco thau others e.c. mot4y1 methaorylato 10 ) end polye 1 ,i4r1Inviteh, 1963). nmoothaoss any be or irportanee prevantion.or -thronbosis. (2) rettrpilltft This is as importzmt chnrsoteriotie in =Intim to the sin or thrombosis and its provocation eroand too valve (see pa,„ 87 It is dotermined thy* an opticel method.(lass at al, 39G1). (3)22.411VadaDD Thin is nn index of the ability. of the toot surface to attract ions presont in the conductive fluid adjacent to it. It TaID determined by noes et el (1961) by tbs oVeamW, potential technique, Fluid V= °rood throuch a cop177h r tdbo (04)0 ..int Ion constructed of tho test matorlal and the elsctrionl potential beftwn the ends of tho onpillar,y tuba sere measured.- This neasurement sad possiblo tho Oalculation cf tto Ects Potential by uz n the equatickofEelMholts. - 78 -

T e i portcnao. of . ZetQ. Potential in the initiation of thrombosis in blood vitt be discussed 3..ater (see page (4) Porositr: Prosthetic Elf.delliala fall into two large Groups (Pate, 1964):

(a) Mn-porous: In which the .function of the prosthesis depends up on tho inteceity, of the material itself, e.g. silicon rubber, and V.M2: in which irVowth of tissue into the pores of the material affects tho function and durability of the prosthesis, e.g. fabrics. The unknown relationalp between porosity and fibrous ingrowth, neo-intina formation, fizasUon to adjacent structures, thrombosis and othor factors may &Aerial= the success oz' failure of a Given prosthesis. Tv proper fabrioatton, it should be possible to produce a prosthesis with a controlled ingrowth of tissue so that the desired biologic function coar be obtained. tresolowaikt et al (1960) attempted to correlate the "water porosity" with the fate of the implant, but as porosity may be conoidered,f'roa the biolor;14 standpoint, to represent epeces through which fibrous tissue and capillaries may invade the graft, simple "rater porosity') does not. adequately define the property. A material can be highly permeable to water, but with pores so weal that cellular infiltration is impossible. Porosity is a double-edged weapon in the case of vascular prosthetic.

According to Daraboy et el (1965), it would appear desirable to have a non-porous graft at the tune of tation to prevent blood loss imiediately after operation, but if .12'graft is woven sufficiently tightly to provent blood loss at tho time of ixaplentaidon, it will al - d. be constructed ss ti bhtki that inGroath of fibrohla,to thvouGh tho intorstices of taa Jft to bind the inner (ondothelial) outer layers of cellular inGroath viii be very scanty. Ana result, separa... tion of portions of the or cO.:i °our, rosultinGin ulceration or cOin formAion. In the trio of heart valves, it woad scam poranzts r is c denim: Use property in the construction or the mane ring in order to eller tho maximum cellul inathand fibrous union beteon valvo and the body. On the other hande porosity maybe undesirablo in the construction or artificial valve leaflets and cusps ttloro tiscue r oe,th till load to thi end Lark, or the leef_' ets with atibsoquont rigidity and stenoain. Anothor factor of Importance relative to poroatty is the diffusion -one =one the prosthesin and the consequent for, tion cif' curfaee Go, (Leflakey et al, 1965). It Nu; been sugGentoa by Saryer and Foto (1953) that tho porous Graft alio= tho tramport or ions across the prosthesis end thin provonts the acemlulation of c lame olootrioci potential on tho inner surface batmen the prosthesis and blood arca°. Thin is supported by t fcot that thrombosio occurs coca commalv if the proethesis Jo total, impermeable to ions. The solid piaz tio stTuctaro has bean considered an electrical condenser thioh till eller A e built?-asp or Lone thich at times coy produco a positive charm and load to thronbosio. The dogroo of porosity which must =Int to allow diffusion of ions has not boon detormined. (vIrsvAt PROPTRMA

(1) LatlaaaaligiO An artificial volvo in immersed in blood continuously. If tho ranteri'al from vhich it is construoted absorbs water to oven e meal de5mes this z*,, Iva to ooneiderable Juana= zathe va3.ve vo12 treidat after aevenal years. The amount of- aquoue media absorbed by the poi or after -Itfrweion for specified time :la eedto rmastwe this (2) Chemicea ,t9tivitvt Chemical in rtnoss to all compounds that aro likely to be prosont the blood (inaludinz common• drugs) must• be tested, as well to solubilitt of thc polymer is the common inormio and organic solvent:. (3) Raitit iAlatt It is also esm-intial Wknoo the effect of urn irra nation on the polymer. Toe effects Lire possible after exposure of a poloser to irradiation: crops 1 and scission. A polymer can be th simphost case to consist of very ?orb; nolccul

Cross 1 ad have ihe effeot of joining adjacent o3veirt5 by lateral lirdw o. valeney bonds. Soistions on the other hands rxtraa the. bre re, of the lone cholas into mg/or-Guess the comequent' reduotion of, the molecular veicht of the pokfmer• This rasults. as evlained. beforos in • cleterioration' of the 'mechanical proNertioa Of the mat,erig araIRRAL • APPI4 atta Oil CV PZAAST/CS •Plastics aro used in the• heart in mace three forms: (1) noulded *end Cest Artkilsass • Mere include thole valves e.g. The Farnemith vc..1.ve and ballet of the caged bell valves. (2) Mums entl nments: no n fored in valve cusps

in constractinZ amine riaza of most valves.

(3) renaa ,Agents: Plastics areoo ionly ur3ed to impreGaate a varieV of porous m :ter-ir.131, or even other plasti'es. Thus we combine the strenzth or ono materiel and we it as a skeleton) trith the exoellent surface properties of another. Polyurethane and silicon rubber are commonly used as improgaatinz agents bemuse they are believed to be less likely to excite thrombosis. To date, at least tori different plastic materials have been used in the eynthesis of tzrtifioiel valves. Table I/ ) gives the chary. terist3.cs ofthese tribute:30es. Table (iii) shows the aomman epp1ioatioas of some or these vm.teriols. THE IIIOLORCAL 3,MLAVIO PROMILTECii Three types ofbiologicalcomplications are WOy to follow the place:wilt of a tie material. in the heart. use ere: foreiga body reaction, thrombosis a the blood, and deatruction of the red blood

T;CS311E =PTA= or rtArICSI Tihen a plastic material is used as a bislocal 3m .emt spouses comm.,/ mar (Colman. 1961): i) It may cause en acute inflammatory episode and be rejected ii) Rejection moy be delved for several months or years iii) It may be removed. piecemeal by the body's own phagocytes iv) It may boom eneysted by fibrous tissue and Main in situ In the last altuations the inpiant has become virtually eaetraoorporeal. Au additiant1 type of response was noted by Canon 1961 lie implanted TABU Il

Pt= CaVIVIES .OF PROSTIMC tiATER/AIS

Subetanoe Specific Tensile Impact Hardness Water Softening Zeta Wetting Gravity Strength Rockwall AbeOz tics Temperature Potential Angle P#ib in R ° F Art • V.

P .V60 • Rigid 1.38 8000 5 120 0.23 280.325 Pleidble 1.24 5000 350 85 0.45 300.375 t PabositOrl 1.17.1.2 700a41000 3.10 U 85.105 0.3-0.4 300.450 MN .methaeryl Polyethylene H. Delimit" 0.94.0.97 00.5500 15.100 1.542 D 41-46 0.01 1100C -13 0 L. Delight' 0.91-0.93 1000-.2300 90.650 16 0.015 110 C

Polyurethane 1.14.3 4000-8000 400.700 AP' Pol,ypropylese 0.91 5000 500.700 1.02 R 85.95 0.03 330 Teflon 24.2.2 2000.6000 100.350 4.0 R 70 620 90 Door= 1.38 0.4 81

Referencee Simonds (1961) 13111meyer (1962) Simonds and Churoh (1963) Mier (1958) bussbuttress =Abel. et a. (1965) Mitre/ valve Beak et al (1965) ring Valve Iktrassel i t al (195) Mem et el (1960)

et al (19614 ra w Polytetraflue Valve ring Beck et (1965) ethylene coating val, RAy •it 09a.) leaflets Braummla et al (1961) Sahlaert et al (1961) _Aortic valve Babas= et el (1960) leaflets

XV *. PORMER.1 Terylene r Aortic leaf• Schisert et al (3.961) Doman lets *ler Patrol valve • Itster & Ellis (1961)

TABLE III-(oon ed)

Author

..,POIngitriAMS a et al (1961)

Aortic leaf t l (1959) lets Isspressa et a3. (1962)

Silastio Valve wards (1961) Valve Crus et al (1965) miaow Valve lens Beek et el (1965) IsPregastion Sehisiert et al (1961) — 85 sheets of poly—tetraflueroethylene (Teflon) in the place of peritoneua and muscle of the internal abdominal wall of rata an found that they booame incorporated in the tissues, covered with peritoneum and permeated by normal /coking blood vessels. Heconcluded that living matter is able to invade the diecontinuoua structure of Teflon, and in doing so, open up this structure to make it readily porous. In general, the degree of tissue ingrowth depends on the porosity of the implant (DeBahey et al, 1965). Dellakay et al (1965) described the tissue reaction to the implan., Cation of artificial valves. Fibrin was laid down in the interstices of the sewing ring hollered by infiltration by fibroblasts towards the internal orifice of the valve. There was evidence that complete healing of the surface was extremely prolonged, if it ever occurs, and that the central area of granulation tissue remained as a potential site for thrombosis, Another important aspect is the possibility of exciting cancer.

A report by Hueper (1960) suggested that implants made of polyurethane may be carcinogenic in the experimental anleels. On the other hand, Harris (1961) reported the results of 16,600 implants uith no single case of en_ignanoy, These data were collected from 184 different surgeons. However, it maybe that moat of these implants were recent and that carcinogenic effect takes a long tie 'to appear. ix 4.1HROMOrria: There is no doubt that plastics excite thrombotis. In a conference on the artificial valves (Yerendino, 1961), in almost every instance, .66. dogs that survived operation died won af as a result of throabosio and the proothetic. valve °Psi end valve not eee=1,to alter these results. floss et al (2961) •studied clotting in pla3tio probes in the superior.vena eaves or doco.ona• founal4at plastics tested were the site of tlusombue. formation within 30 minutes.. Prater aria Mlle (1961) found that oil types vOl vec constructed. fra3 several plastics. owned. clotting after insertion in ocoriine hearts. .Clotting seared to occur even with prolonged nation. Kialf et al (1960) found thrombosis on several Ines of plastics even while systemic fibrinolysiewo used. Although it is. agreed that formation of clot on pros.. .thetic valves is not as serious a factor in the human heart as in the dog's heart, the aeveritj of the problem in the cosine heart has made it very difficult, to evaluate adequately valve design prior to clinical

Ito following factors maybo important in the initiation clotting.

Roy 11001 tile tom Purf./19.1 anootimoss of the intim was considered. to be the most important quality for the prevention cf thromboeis under plvsiologioal conditions* but clotting is only slidatly more /*alone:4 on emooth surfodes (e.g. oleos, Detbyl.methaorylate. polyethlene) than on plastics with a rough surface (e.g. Teflon). 'Also oarly thrombosis has been observed in ti yr lined. experimental vasou3.cir prostheses of polyethylene, po ion, polyurethano end methyl meth/tor/late (Uirknvitoh, 1963) ettabi; it/ i tbn-wettabilitur vas =other attribute of the int which tea Considered to be essozatiel for the greVention of 'ntravaecalor bleed elottinz. It toe elm believed that a meter repellent surraee would necessarily be blood repellent (ttirkotitchs: 1963); Rase and ',wide. (1954) tested bleoa. 'clotting on intravasoulez plastic probes and found that a Clot ceneraky adhered to the =Peep of the wettable plastics but in the case of the less vsettable substances lubber; the clot formed in the centre of the atream. On the other boa, the elOttinc time in test tubes of Various otibstozces could not be ted to vettabilitt as =aura by the biro of the contact angles; between the tater and the surface of the Also experimen_l yaw:1144r prostheses ma2e (es rester repellent material° were mauled by thrombi after their implentetion into the unit body (tarkoritch, 1963). puregpe (77,a) 3 otentiol It has lour; boon hnovn that elite blood cellos red blood mils, fibrinoom and other proteins are vocatively charged at the normal. pi! of the blood (Gott et alp 1961). libreeson (1925) vas able to demonstrate that the white blood cella end shod platelets climate to the positive pole of an ebootrto cell. In 1953 laver and Pate demonat ratod that the normal potential difference across a blood vessel wall was 1 - 5 m. volts, oath the blood or intim relatively neiptIve with respect to adventitia. Thej reported that injury to the intim altered the nor ml potential differenoe and don the tronaaurel polarity was reversed the ietieapositivo with respect to the advent tie, throdboeis freepent.. ly occurred. Recent'. data about the 'Origin of electric phenomena• on blood vesstasindicete that metabald processes inn .tie intim or in the vessel wall nay. be directly responsible for electro.negativity'of the intima, the exiotence.of potential difference and.fnr changes following trauma. The or .gin the negative charge on the turfece of the rod blood ce11 1$ not ci The negative charge on the white blood cella mey be one of the enplanettons far the : cation cf polymeepbs. towards eleotropcsitiveloci of inj inf1emm t ion, anoxia, *to. Mirkovitoh, 1963). ?he negative Charge on the latdleta La of the same.magnitade as that on white blood cells: Valli= and Carey (1959) demo trated that if negatively and pod:timely charged. platinum eleetrodee ware placed externally on opposite sides of the rum4 n boiler vein, a moderate clo 4 developed on the vein wall nearest to the podtive electrode; they concluded that tiosue damage from the ourrent,.rather than electropositively, caused the thremboeis. Sthearts (1959) iaa a similar etudy observed that'elotting occurred in en 000luded femoral vein enolosed in .a positively charged platinum alrmth. but not in vein unclosed in a negatively charged platinum aheath. Ieparin prevented Glutting from ni•th. the • positive field. ricoumarol did not offer this protection. 'The differenoe in effectt of the drugs was partially attributed to taros .largo negative charge of heparin. en the other h Rocs et al (1961) believed that no single physical property of t:le. surface of a compound determines its coagulant effect, cnd that the concept that the clot-promoting effeot of a foreign substance is inversely related to its wettdbility or its positive surface potential, is not justified, He thinks that a specific chemical reaction, rather than a general surface property such as wettability or charge, is responsible for the coagulant action of a plastic. alleoflinamio Factors: Haemodynamio factors are very important in the genesis of thrombosis of blood, especially after intraoardiao implantation or plastics (Mirkovitoh, 1963). Damage of the endothelium by sutures or the sutures themselves, in some instances, appear to be the site of origin of thrombosis. Starr and Edwards (1961) introduced a modification of their valve which excluded the atrial side of the suture line from the circulation by means of a retractable silastic shield. This has resulted in diminution of clot formation on the prosthesis and prolonged survival of dogs even without anticoagulants. The same principle was used in the mitral valve devised by Malowney and Paton (1965). On the other hand, techniques devised to bury the suture knots do not significantly influenoe the incidence of throdboembolio phenomena (Maker et al, 1965). III • HAEMOLYS/S: Anaemia following the insertion of prosthetic material was first described by Rose et al (1950 in patients in whom a HUfnagel valve was implanted in the aorta for the correction of aortic incompetence. Later, anaemia was found to be due to meohanioal destruction of the red cells by the prosthesis and the haemodynamic changes produced by the artificial larnoff and.Cesii 1955; ' Stnbatrum et ci, 1956). `rayed at al (1961) described•6:patient iathialtussolyticanabeia. followed the usa.af a Teflon graft to repair 06 atrial °opts' defect, InAravaa. culor bee:Daly:dab hoemoglobinUrea and haessiglotinaamie were atiiibuted la this case to the collision of t: rod blood cells with tho enact:Ian/alined parts of the graft be se covering the raw surface of the Teflon at a second operation corrected the -anaemia. "iClor otO1' (1963) end Veruden eta (1963) have described similar blots of I analytic anaemia fallowing the surgical correction of condo cushion defect ° with Teflon amens. CherAcally.inducod haamolysis. is Sines Teflon and'other plastics used in the prosthesis inert ana incubation of e t tea tith Teflon does not result in haemolycis orclorphologicel ohanije of cello (:'ilex: ct alb 1963). The collision o tea Td the rigid prostheais seams lil oller to rodu niztion and haemelysis than the surf"oo characteriotios of the prosthesis Stevenson and Parker* 1964.). Brodeur et al (1965) studied the problom of hat a3, to before and after aortic ale mitral valve replacement. They fault that the majority of their patients with aortic valvular dime° had a dlidetly Shortened red blood ccl1 survival time, bane were ranarm% but one patient had findinge oompatible with compensated tic anaemia. Th47 felt that it toe poseible for patients with aortic valvular disease to beoome tnnacni on the basis or traumatic haemolysis of the erythrovios. Men those totter- studied patients 'who had had prosthetic rep ace- meet of tho aortic `Val t's , found th!:.t the ma cell survival was • dh rtened on amount strilLr to those patients ulth Lortio valvulSr Ecorse. It el as if turbulence prduced. by lc diseased aortie vaiw haa been repancea by anothor. equal turbulaaoc in tic posLoperative re loa due to the artificia valve, so that the tame mechanical Soros :ere, bo amlied to the red cell mectsac to cause. Jaen :lased destruotien. Underthean coalitions of a pre-existini„ chortmea erythrocyte survienl, :the :addition of a minor traucatic aisturance or the occurrence crow° turbulelee would o expected to ineroaso the destruotion or hrooytes. If tra:ma or turbulent° were severe enough the bongo 'germ:evil/A not , o al:lo to cope W. tho rodeo/2 deficiency ad anaemia reuld beeomo evident, Development of rezurcitation around the vol.ve could bo ootot to cause additteAal turbulence Lnd rythrocyta des. '..ruction. prodeur et /96)) found that tho insertion mitral ana trio- mid wave rrostheses dV7, not decre,se tho ellithrecyto uurvital as comarod vie ntients tith aortic prosthosoc oraortiOtalVe diseases The Mau aeven the nitral cna to.ic pia valves a--1 1c; di<ole occurs under.lower. press. .e than the flea auxins ,thc ciortat valve. They emoludea th.t th tmobulonee produced by rattrt.2. tua tricuspid proethecea in ler.n than th rrolmea by cort1 c proathet;et aa, th the to produced by elc low pre3oure 47yotcms or the triaas?id Lad mitral pros. theca 5a not serioictt to aria aicfican y to the raw: of destruction oryerecytes. On the other rezvraitation around the Lit:- valve prosthesis

— 92 • occurs under hill's. preseure durin gyatole. m5ula beempeoted to increase irehmacardiao turbulence crea shorten the red cell aurvival time. couguiciqs Three sat; • of criteria serve to guide the choice of the proper prosthetic materiel for an artificial valve: Ayala/as ohemioal and biolocieal. be physical properties the ee-iest to estimate experimentally; yet oxperionoe has shwa that the behaviour of Prosthetic reeteri:2., c in the heart is it to their'behaviour expected on theoretical and experiJaentel creunan' 41 This discrepancy' became clear only a short 'chile efter the use of leaflet or sleeve valves.. It me soon realised that all the prosthetic mater's used mere sitareV unable to vithstand the repetitive fold". Strom'. d opening closure of leaflet Tel= under the normal left ventricUlarpreeture vithoUt &maturation& a4iffcninr and te inc. East of these valves performed 0110M derinei; torte in. pulee ioatora desigeed to imitatethe ae strozaess but all. e. them failed in the human body. The rade= for this mey lie in the off is of the arsvironment of the valve in the heart, i.e. blood and tissue fluids. In spite of thielimitation, proper kncvledge of the phyzicel propertiea prosthetic materiel Serves an. a resins guide to'its fitness for valve cenureeture• The cherdeal cr3.ter4 cro • the easiest to comply eith, as most of - the materiels available for valve genthaele ere Chol call,y inert and =cite little or no effect on the body fluide. the tiseues. Dielocical behaviour of prosthetics, calico in so far as — - induetion ia =Owned, difficiat to 'zealot and 30 unr,t1/y• -the' caueo- oS.'- their i'ailure. • The biol.° cal properties. cannot be aeterzined. by in vitro eve tal 'oven aay.o. oxperizonte am -oft= dinc, -ovinc; the variable alottLn -rxehaniemalu clIVelvat,epoeicz. . The Pinal • ezeitraation: of the catitabIlity or mtertal fo sez .r.:•Irroethatio valyc iz 11. bohaviour..in - the oty, FIAPT'rit. vx,

In desinning an ideal prosthetic valve several aspects of valve function runt be ceneiC.croa, I 1. vUTII0 001ZIMPI.10;75: Prot the hydreulic stnapoint, the valvemuet allow as uueh blood to flow as is needed by the body. and it must be.,competent The normal cardiac output is on the averace five litaes per minute,•but as the flow period (diaatolic poriod for the atrio-ventricular valves awl the ejection period for the oo -truncal valves) constitute only a part of the cardiac vole, the actual flow rates though each valve per unit time then the valve is open, to much more than the cardiac output* In a resting humen, the diastolic fillinz phase constitutes about C0el' the cardiac cycle at a heart rate of 70 per minute Lombard end. Cope, 1919). Thic means that the flow rate through the mitrel valve aurin dtootolo is about 9 litres/minute (Lewis et el, 1952 Durin; severe exorcise th • mrdiao output of en untrained mammy rise up to 25 litres/minute (in athletes it may rise up to 35 litres/minute ). The heart accelerates at the same time* Lodberd and Cope found that co the heart rates increased, the period occupied by diaetolo relative to the total cycle lenzth aininiehea procreeeively to 25,7" the cycle lonzth at a aeart rate of 115/minute„ lath a eardiao output of 20 litasee minute end die.: tole oely. 2r ownof the cardiac cycle, the blood flow across the mitral valve durin the opening phase is about 80 litres/minute. The flow rates across the aortic and p valves during the ejection phasie croearen higher than those calculated for the mitrel valve because the ejection phase constitutes a smeller percentage of the cardiao cycle than It003 the diastelie • filling period. Arcial valves must; be designed to alloy flows corresponding to the normal mitral and aortic blood flow Burin : rest and else during moderate eaderaise with little or no gradient. In desi r a prosthetic valve that offers minimal resistance to blood fJ.oe two aspects mod to be eonsidareds the orifice and the mechanism. UT hydraulic efficiency of orifices of different shapes can be judged by comparin their inefficient of discharep (ceo Chapter Orifices with sharp edema behave rather poorly mainly because of their high contraction coefficient (CD about 0.60). In addition they favour edkving, stasis ana wide boundary layer formation on the distal side of the orifi Orifices with rounded entry and everted. egos offer less reaiotnnoe to floe and are leas likel, to produce turbulence (CD = 0.90. In addition, the beet meohanies is obviously that which is complotnly removed from the flow pathway of blood. Both conditions are met with in the normal witrel valve. The ideal proem llamas is the ono that copies exactly this ideal design, i.e. deadened au a =mei valve. Such a prosthesis had been used by several workers e.g. Prarawald et al, 1961; Bahnoon et el, 1965) both in mangle and in humene. Bowover, un spite of the asoollent hydraulic characteristics of these valves, they uniformly failed because of the poor fati gue rosiatanco and inatlosuato folding endurance of the materials uses in their manufactures The blood has to pass notenly.thraugh the, or5.fico (or orff'i000 ) of .the Jroothotio valve rinL14 but alto th:.-ough the left ventriculnr Outflow traot olvits the Lorta. If he outflov trot or the Aortic root.ars oeesplea partly by the valve mechanisms the remaining :fres areamot be sufficient to allow the passage of the cardiac output.

C41 the other hands it B kno7n that the aortic orifi must be reduced to an.aroa or less.t, ono svarecm. before haemotrna.ni, cally ale- nificant obstruction can occur Luisada Lius 1959)0 It can thus be ox;)coted thr;.t.LI:lima encroachment on the loft vontrioulnr outfl ow tract or the luzon of the ace endin aorta must occur before physio10.- • gically nicnificant Obstruction can ':o observed. The vnlvo runt caum the to'- at ponsible turbulence or di,,,turbancte o blood stmaml,nos. St must eauno a small ^y layer andlittlo or no oche zori so Tt:oriments by Davila (1961) shoved that valve zones ani'boun3pri :layers are usuall,the pito of thrombus formation. •

ILEUMELE.P7rDnnAkAM71 From the moo., nionl standpoints the valve mgt open cu close vith

the least llossible resist:Too. Any ros.stnnoo to c •C war dol'y attnInment of full orifice lortcn cZcetion cr the disotolic filling periods. Re intent:8 to closure may cauco tho mitra prosthesis to rem in open etor 11.1:c loft v-n•4T1oulerprosent15 ricea above the loft atrial rrossuros and. mitrol incompetence rmyftlIvr. similar meoh

,induoo- aortio motor= in the ease aortic prosthesis*

-97-

Three. factorG contra 'the closing and opening limas

(i) 9i-filk(7-r(m1A-7 419444 bVi'103 objeot in fluffq stroa/, trmas uith 4 voloaity inve proportional spoolfio gravity. Objects hoavioz. than the fluid in which they travel aro delayed by their Imrtia. is caloa• the ,t4e,a dna can be oaloolutod are follows Davila' 1961)1 Velocity' or Fltild "V" as Faorm al` Mass or Velocity. or Objeat "f" i.C.SS O. Inertial lag = V 'hurl the higher the speoific gravity o the pros tho trap-door (or bcfl or leaflet)* t :e care'resistance till It offer to ihe blood +stream during openings:Id cloware. Therefore, tho - ideal prosthetic =must the dame specific gravity as that or the blood. (2) Octant!) the '1oche,91aFi1lak to riol:

color ger diatoms is, the lonGor 1 the needed for closing acv opn; valve. In addition tibia distance is

tor long, tho Ma nay impinco the oPDcaite toll of the vont.

riole and (ley imitao the ilyoo:rdi (n the other hand, tr this dame° too short, the valve-twins:0 may be restricto4 and a high Drossurc orLdient aoroas the alveV may reault. s.,r =UV, a valve ring with a toloscopic ca o,vri;;~, it al (l%3) deterolnnd the ralnimni cave length oonaiatent vit:1 optimal hydraulic re"ore aco in tho bell- -edge valves. Thia length wad fo to be 2 3 tits tho bail dirzoter. t.n;..pevirr.te on the tail valvez sore

perforcza auring..this sib • and.repulte ttU be e3.ven in a eubsequen ecotion .Chapter.;X

e into aro olUineted.:Oota,pleteVf440 bon.veiven$ liormerznith valve' Lentieu4TIrelvesiseoia velyeeoprthe Lillchei ominous, pros.hecia. • . Other 4etligna, fug* Cottto butterfly yaw. Peres laonocusr4 valve 12ave•n joint with finite resistalace• The jointleoo

docigno are definitely superior* both :beesoae4?.ey stvlity the otrueture

• I , aril bemuse they aro far lees liable to break dew. (rdn;

FrOL, the anat ,rale4-1 sandpoints the 31 proothesis taunt oocupy 17 13ttle epico thc left ventricular cavity-- ona must not interfere with the bloc.? :r.1oz1 1-42.:47.or the left ventrieuler centraetiuns, The mitral.valve plane 4.0 =ray p rt 11 wit't that of the lens axie of the left, ven•rlole &ulna Rystele$ any makoo nearly: a siert ei with the plane of the Oortia:ittave. ..The:•4ileal-raitral..proethecie rautit ve the long: curia of ita mohnnism t; el with tie TIone o ito rings .p bet: i4.1.4‘.12 the lonz er the left; ventricular cavity, roothesee with their mechwnt ;43 bulEinl; ridtt onclop to the piano ,cis their rills t3 interfere t io cannel oontrootion oru the bleed elm in the

outflow tract on t.ho lay t wntriole, On the other hand, " ideol•

aortic proothosiz should. hnve...the .10ne azie of .ite•Peafa'anial yr1th- the lenc a.nis the occonaing nor pIOLCGICAL COMID, of

The main biological oo re' ions n design of a prosthetic valve are thoso pertinent to induction or thrombosis c haemolyeis of the blood. Test of the necessary factors in the design that are required to minimise thrombosie E-4,0 else important from the hydraulic standpoint and have already been discusced. For the sevention or haemolysie. minimal maohnntoel trauma is essential. Redrcing the areas of impact beton= the various perta of the valve on avoiding turbulence =7 help In this respect. c(INwsions In summary. the desirable a o s It rust offer rtivArri resistance to bl,ocd flcre. It Duet cause ninical turbulenoe, wake areas and 1.1) eyer. must be conpotant. It cruse t be easily star3lisvas thout denaturation or deterior.. ati*n of its mechanical characteristics. (5) It must be chemimil inert end cause no ti.asuo aetion.

(6) It must be able to withstand the type tresses

to which it will be subjected in life for an to period of tire.

(7) It must offer no interference to ventri ontract3.an or to blood flow in the outflow tract of' the ventricle. (8) It must be easilg and rapidly fixed in the human heart. (9) It must be as light as possible. (10) It must occupy a small space in the ventricular cavity.

:TIAralMaTft"- *,)

Throe .v tiez of tho riammeremith valve have been • rted into human Werta s hove been funotioning for riods ranging from a few days to 20 months*

Th..) first valve (rig.16 original Ben tall and tiara s° (1%3), consictod of a ring of ulrir 'shape and a self retaining, flattened lenticular trap c mechanism)* Thia tree-door IMO suspended frac) the ring by throe curved legs* T.he depiza vas .pz :3.1y intended to dispense with the cog° used in the balli.ond...caDe valves* I coposvity in tho ring cocoa:iodated the sewing

collar which eonsisted of two steel wires on which U13.3 mune a poly.. tettlafluorettqlene (commercially kamea as Teflon or 'Mum) tape. This 3 surrounded by a piece or polytetrefluoroethylons mesh* which me sutured in place by a throe made of the ears material* 'he Mark XI rammerstp.mith valve (rig.16 mas inft"oduced by tho conjoint tor ce .7, Mem and Aiverez-Diaz (Melrose et al, 1904). it consisted of a circular ring on which there were two projections sep- arated by a distance or about om-pthird of the oirc=fcrancs of the ring* reechoni= consisted of flaUened lenticular trap.door that °lightly lnrgor than the orifice and ran suspended Vron tho ring by two -101-

Mark I Mark II Mark III

Fig. 16 The Hammersmith Valve 102a.

curved legs whose movement were restricted, by the two projections on the ring. The two legs were eccentrically situated on the lenticular trap-door so that after suspension, the trapidoor fell may from the ring at the aide opposite to the legs and the valve trine° was mainly directed to one side Actually, this valve when considered outside the heart, had. two orifices (Fig. 17 ): the inlet orifice, ipe, the orifice bounded by the ring sinus the areas occupied by the two pro- jectione and the two legs; and the orifice of the outlet which was orescentric in shape and eccentric in position and situated on the side of the valve opposite to the site of suspension of the mechanism. This eccentricity of the orifice was deliberate and was made on the assumption that it would, when put in the proper place in the heart, "direct" the bulk of the blood to the area of the ventricle most able to accommodate it; namely the area next to the septum below the outflow tract (Melrose et al, 1960. Two different sires of this valve were used and are working in human hearts: 2.00 om. and 2,25 cm. internal orifice diameter. An additional sisal, 1.75 cm, internal orifice diameter, was used in animal experiments but not in human hearts. The ring of this valve had a concavity which contained a sewing 'collar similar to that of the Mark I valve. The Hammersmith Mark III valve was developed by D. G. Melrose. The purpose of the modification was twofold: firstly, to improve the hydraulic performance of the valve orifice, and secondly to dispense with the two cheaking projections on the inner side of the ring, which, being stationary protrusions in the blood stream, could invite clotting.

- 103 -

Fig. 17

The three orifices of the Hammersmith valve in the heart during systole

a.

(a) Left ventricular systole (b) Left ventricular systole after after Hammersmith mitral valve ball-and.,cage mitral valve replacement. No mechanism remains replacement. The cage persists in the ventricular cavity during in the left ventricular outflow ejection. tract during ejection .1011.e

The Hark III valve consists there is a narrow lone- ituit4eta protrusion occupying about ter of the total circum'. Terence of the internal orifice and abou in breadth. From this ring a lenticular trap-door is suspended by three curved lege, unequal in size, Two or these legs are longer than the third one, so that the discoid maahanism is suspended obliquely from the ring and the outlet orifice la larger on one aide than on the other. Here again we have to consider two orifices for the ieolated valves an inlet orifice consisting of the area of the intert orifice minus the area of the three legs; and an exit orifioe, eccentric in shape and situated between the ring and the trap-doar. However, with any of these valves inside the heart third orifice has also to be oonsidered and is perhaps the most important one, This is the one formed between the edges of the trap-400r and the inner walls of the ventriole ). This orifice varies in size during the various phases of the cardiac cycle owing to the change in the internal dimensions of the ventricular cavity, In all the Haerarsmith valves, the exit orifice of the valve has an area which is equal to, or larger than, the area of the inlet orifice. With the advent of the Hark III Hamwramith valve, a new type orso enz collar loused, This consists of a polypropylene ring surrounded by a few layers of polypropylene, mesh which are stitched in place by polytetrafluoroethylene thread. Two rises of the Mark III valve are made and implanted. in human hearts. Time had internal orifice diameters of 2.26 om. and 2,5 an. - 105

Table IV 'gives the exact measurements of the oomponents of the different varieties and 81506 of the HeAraeremith valves. It vial be noted that the moat importarit anasuremmt or the valve from the surgical point of 11817 is the external diameter of the valve ring, as this diameter must be equal to, or slightly loss than the hum= mitral valve annulus in which the prosthesis is to be fixed. This external diameter wan found to be 2.7, 342 end 4.0 ea. for the 240, *25 and 2.50 on. valves respeetive3y. 'The more important oriltos from the fano Lionel point of view is the internal diameter of the ring or the lo orifice. The ratio between the external 'and internal diameter:: inlicates how much of the external diameter is wasted from the bydroulic standpoint. This'ratio was found to be 1.011 in the rark I valve (2.25 co. internal diameter), 1.511 in the Mark II end Vark III (2.25 internal diameter) 1.64 in the Bark XII valve (2.50 cm. internal diameter). Another irportont measurement is the maximal distance between

the trap-door end the ring, because it is a measure of the protrusion of the valve mechanism into the cavity and the outflow tract of the left ventricle during diastole. This distance vas found to be 3-13,rems in the largest 'rark III valve. VALVE: y.1.191Tat She valves were weighed bye Mettler wet e (A. Ilett3.er3 Zurich, Switserlaryl , which has a sensitivity of 040005 gm. Table V givea the weights of the ring, is door and the total weight of the different sigma of the throe ilaciaermnith valves. Character Mark 1/2 2.25!e 2.26 em 2,5 cm aternal ring diameter. 3.4 40 Internal ring diameter ma 22.5. 3.7.5 .5 22.6 25 (twaratd.ic orifice) Inlet on arc a (aa2) 2•4 4.00 4.9 Exit orifice area (cm2) 3.0 5.3 5.45 Trap-door diameter (um) 21 25.5 28 Angle between meohanism and ring 28° 2 25° 12 Ring thiolaiese (m) 6 6 7 7 7 Ring breadth (cm) 5 5 6 6 6 tkr., distance bet:men ring 13 13 10 " e ft 0 0 0 3 San. p-door c erect (mm) 13 5 7 10 55 Average leg length 9 8 9 10 31+1146 3.3+13+10 Dimensions of the protrusion (wrz) 3 4 2 14 107 •

Valve 't7e ght of the. the tat Vireight Trap.daor gm. gm. gm. Mark I° (2.20 343 o.747 4.58 ark I (1.75) 1.79 0.86 2.65 (2.00) 2.25 0.91 346 !Jerk II (245) 3427 1.37 4.65 Mark xxx 4.20 2.86 1.00 3.86 k XII 2.50) - 3.25 2.26 3.0

It will be noted that: dues to the excludon of the metallic elements from the valve and to the ow specific gravity' of polypropylene ( .W1 is the lidateat plat tie known) the valve has a very low weiOht* This is a distinct advantage because theatre" • ring moves up in each diastele and down in each systole carrying the weight of the valve. with it. V*91pUMN OP TRE

Table la Gives the volt s of the three different valves* This is a the degree or on the left ventricular volume produced by the meehanism* volu of the trap-door of the largeat valve now in use (the Marklils 240 am* internal diameter), vas eniy:303'mny, :This is negligible in relation to the average end-diastelio volume.of the left- ventricular cavity' 100 ml. Arvidescno 1961)0 Uoreover, in patients With atral inoan- tenee*.thichAs the commonest indication for mitral valve replament, the voluma of the loft ventricular cavity is increased, so that the volume of the trop-door•beoames less then Vol' the /eft ventricular cavity volume RPRCEITP.10tED 1 pOOks

In the Hammersmith velvets, the trap-door• diameter wasfound to be 2,3; 2.55; and 2.8 on. for valves of internal orifice diameter of 2.00; 2.25 and 2.5 ore. roalloOtivolar0 The areas of the trap4loors CL these valves wore 442; 5.1; and 6.15Ae reapectivaly.. The total force applied on the tTep-door during .a peak left ventricular systolic pressure of 120 rsa Hgtms calculated and found to be .1.5; - 1094.

Vans

tbrk 2.25) 3*9

MarkU (1.75) 1.0

Nark U (2.00) 2.3

Mark (2.25) 3.3 mark m (2.26) 1.1

lbrk m (2.50) Jay 0 •

1.8 and 2.2 110n2, for the three v, mines (see page 71 This force must be borne, in t final analysis, by the somas of contact. between the trap-doors and the rings.. The areas of the contact zones, were found to be 0.19, 0.21 end 0.23 inch2 fer the three valve eiees. Consequent1y, them contact sows snot bear a force of 7.95. 8,65 end 9115 lb/ie, in the three valve etees, &wing ventricular systole*

- CapIESTST PP MUNE* Polypropylene IS ma po ...nation of propylene at temperatures and pressures a little above atffiaephertorwith the aid. of certain cembimations:Of metal alkyl complexee and transition metal halide© ae:ca, ts This methodmas first described 17 R. 4081ar (1955) and O. Iatta (3.955) :The sUbetance is produced.= a large scale in the United gingdom by the-I.0,1. Companyunder the,patent aeIeropenthene (I Ca., 1962),, Propylene itself is a co1ourless. 3.s whose ohental formula is 1341,14I3a Its molecular weight 3.s'42*08* It belongs:to the Group of olefins hydrocarbons and is a by-productof alkylate gas- oline reining (11471meyer l962). Nolecular ,7tvuoture:' Polyprppylene, like many other polymeric plaatice, is not a cinglo Chemical. entity. . Durtng polymerisation propylene molecules join each other in three different ways to produoe any of threeptruotures with a different arrangement of-molecules in space depending on the conditions of polymerization 1962). Natty (1955) give these -111 ..'

tbree the·MJ!lOfl of Atactio.. Isota.ct1olUld~d1otact1c.. Their $truotures are aa follows ~ BRH H ,II n H I I I II I I Ieota6tic: ... C ... 0 .... C, "",c ... c .... c - c .. ' I II I I ./ I' II ClJ.,H m, JI. OJ) U \, ~ '~ ~ ~ 'l '" 1 \ "i'\ ... c-c-c-c-c""c .... c. \ , ~oA, f~ ~ !L C1~ J

Atactic,'·,' H Oft, .. H m:~ n H' H c~ .... cI ... cII.... c .. cII... c .. cII... cr -eI •. I I II ,I I I I .' n n en, n ca,H n H

• , f " t llladep~ ~ AoompoUDd. . fIom fmG th•• three"ohaiJla nre17, it tmn".ez1ata. ,The a'faUable pol1Prcw1ene sa actua11~a. ~,ot tbe.... 'lh~ pl\Ya1ea1 propvtlea or the three•..,0UD48 "farT . . ,',' . ocma1dembly., tmd u 4U'.teren\, batobes or po'lypl"OP71GDe oonW:a. .. . "'.', ' ~ propori1OD80t eaob of' tbeee aubetaDoea, brei. appreo1ab1e 'fariabni\y in their exact ohedc81 ana. plwdoal propert1ea. ,The 'ba.ic 4it1'erence between these struotures u hot _hUe 1M Ieotaotio an4 _ot&otio' VPes are ,higbJ.y' orystallln8 aublteDoes1d.th

!deb mel t1ns po1l1t8, Ataot1~ polyproPylene 18 an 8UlO1',Phoua rubb.,. non-o:r,ysta11SDe subatance nth e. 1011 melting point. flO the .... Ataotio we:in the m'''', the less iB the Ol78taU1n1ty. 'lbiB trill 1~ the 't'lta1 qualities or the plastio, 1.e. loWer ~ point, le.8 atlffnesso less a stren„ 053. lea of polypropylene cal be affected by the o ns of Sem ton process itself. Thus the p peasti.e cs£ .a mein polypropylene contorts only apnrozi.mt y to the data given or elostftre.

ropy r has a spa ter 11 0405 end i.t is, the lidutest piastiO Imorni Its is 285 •325°1?

(about 138C). Its re or 165 75°C).

The high malting point shows well to be sterilised ea allows the plastic to retain its ea oelient me easel qualities et Mai temperaturc,s (lillsoyero 1962). t!eohenioel, Pray ertiss: The velues of the mochzmi oht r cteri.s ene are given in Tolle VII. Chemio9. Prone7sties: (a) 17ate r b PoUprozdene extremereels at to eater. It absorbs leas than 0.5% of 11103t: acpous reedia of storage for six months at 60°C. It absorts 0.0V rater tailoring immersion for 24 hours at room temper.. tura. (b) et en ,ic exul inccermaio tileatAt Polypropylene ie highly resistant to concentrated acids argil It 1.3 °Aso highly resietP.-nt to most Organic and inorganio solvents,

(o) rakt....1.11. a ons There is little oross4inieing when this material is =posed to 313

Yield Arose Mukalla* at yield Towne strata* (ultimata strew) El tic* a►t bra& (uit imato elongation) t strews (IND) Hardneas (Roe:) 85400 ray irradiation. The dominant efteot is that es sei the molecules with conseementreduclime of the mo This is followed by deterioration of the mechanical properties polymer (U.K. Atomics Energy tnthority Research Group, 1964 (a) (.arria04? PotentApls

Polypropylene has a negative surface t of about -13 (Ross eta* 1961). .22EgaZ It is relati to design a good orif ce but very difficult to design a mechanism which is ocmpetent takes imn1 space in the ventricle, does not interfere with ventricular contraction* has short opening and closing times, causes little or no interference with the flow stream and can stand the stresses in the heart for an indefinite period of time. All these criteria, with the exception of the last, are met by the flap or sleeve valves. However, these valves are not durable; and until a prosthetic material with very superior folding endurance and Chemical resistance is devised, soma of the hydraulic and mechanical ideals must be sacrificed, A self-retaining mechtuaism is very important* for this type can "disappear* from the left ventricular cavity and become a pert of its wall when space is most needed, i.e. during eystole. With a self retaining mechanism, the outflow tract is completely free during ejection (118.18 ). During diastole, the outflow tract is occupied by the mechanism, but this is not important as there is no blood flow at that time through the outflow tract. This type of mechanism does not need any mechanical hinges, and in free obvious Badman.. ges associated with them. The present design of the Hammer natural outcome

of these oonsiderations. It is not an iii rOS but it is the best farm of design available at the present time for the slow flow conditions at the mitre' valve. It is important to understand the disadvantages of the various types of this valve. (1) With the Mark II valve, the orifice vas de wed to opeit nowimelly in the direction of the outflow traot and a great t of der hydraulic performance depended on the proper orientation of th r valve. This vas not always ideal. The distorted anatomy of the tral valve at

the time of valve replacement led to plccemen ri lave with its maximum critic* directed away from the out mot in one patient. This seriously impaired the hydraulic performance of the vial (see Chaptarx). The Mark III valve overcame this difficulty by offering an adequate orifice all around the valve. Still the merimel orifice la placed in the direction of the outflow tract, but with the near design,. errors in place ment are not of vital imporienoe in anterminingperformanee. (2) To reduce the resistance cf the valve fluid flow, the valve orifioe vas enlarged at the expenoe of the ring breadth. This in turn, neoessi- tated enlarging the diameter of the trapdoor in ardor to elope the large orifice properly. It soon became clear that this had been achieved. at the =pence of the area of clearance between the trap-door and the X 3.6

ventricular wall. In the Nark III deaig this was avoic by in- creesing the breadth of the ring and so reducing the diameter of the tTaleidocr needed emd alloz.ing enough space between the edges of the trap-door. ana the ventricular well for blood flow. It is difficult to calculate the clearance area inside the heart. The assumption was male that the ventricle isdicped like a cylinder (Davila, 1961) and that the oircumferentlal area between the edge of the trep400r and the edges of the valve ring munt at least be equal to the area of the inlet orifice. However, the ventricle can aezume the shape of a oone during contraction and so the mall my come sommhat nearer to the edges or the trap-door than the breadth of the ring end ccnacquently the clearance cone area may become less than the calculated one. This can be compensated only by further increasing the breadth of the ring.

(3) Another diaadventego the Hammersmith valve design is the presence Of a tharp-edged ring. The poor flow characteristics of sharp edged orifioes have previously bean discussed (see page 95 ). The sharp edge of the trap-door adds to this disadvantage, and also favours the occurrence of turbulence behind it (i.e. on the back or the trap. door) at high flow rates. , In addition, the lenticular design make?' the trap-door thinnest (and consequently weakest) at the place where strength is most needed (i.e. the area of.contact between the ring and trap-door) It is believed that rounding the internal edges of the hydraulic orifice and the edges of the trov-docr will improve the valve's hydraulic performanoe. 317

e mechanism can be also changed 'licm a shorP rounded edged disc, thereby molting the trap-door in the contact

tween the ring trap-door thioker and stronger in the exitsting &magas.

'Idle choice ci prosthetic: may of materiaal must stand the e heart conditions, be inert, excite no foreign tissue scion, be cater repellent, d and sterilise and have a gravity near that of bl 1 other known material. is 5000 psi, lightest plastic knoun, h of 0.91 an ta

Po tial of .13 It is accapletely inort reaction. It suffers from one &soft the ease with lah its molecules undergo mansion tam exposed to irradiation (e.g. repeated angiocardiography). This difficultly could be overcome by choosing the rieit grade of propylene. ,.118 ."

EppRIMENTAL A,LR AT 0 ozpittolmm c v

yea t tasted for their hydraulic and wet propertdes in a pulse duplicator. If their behaviour then proves satisfactory, experiments are then oarried out in the anima laboratory store in addition to the above :mentioned tec aspects, the biological oharacteristios of the valves are also tested. I. ON ME PULSE IMPZICATION

Testing the hydrau110 valves the estimation of the resistance it offers to rear fluid flow, the degree of turbulence oaused it and its

(1) 110Pd tepee to Flows This is usually estimated by msasruing the pressure gradient across the prosthesis at various rates of fluldflow. Curves can then be oonetruoted describing the pressure flow relationshipfor the valve. Continuous (Xesdi et al, 1964) and interrupted (i.e. pulsatile) flow (Harken et al, 1961; Lillehei et al 1963) sere used. If pass. tile flow is used, the volume of flow, the length of flow period and the mean pressure gradient during the period of flow must all be knosn. In order to arrive at the valve resistance to flow one must again calculate the flow rate per unit time and then correlate it with the mean pressure gradient, i.e. to render the results obtained from pulsatile 119 flow comprehensible from hydraulic point of tier, they mus t transformed mathematically into continuous flow. In addition, no single puleatLle pattern or a limited number of patterns can be of any value in simulating the heart. The heart changes its rate oon- tinuously in relation t the bo8y needs (and in cases with atrial fibrillation it chan es its rate from beat to beat) The change in rate is accompanied by change in the endoliastelic volume, strength of contraction, rate of pressure rise (dp/dt) duration of ejection, duration of diastolic filling phase, and stroke volume. pressure on both sides of the valve also changes aaeording4. No pulee duplicator can change ell these parameters. In all the available designs only pulse rate and duration of systolic ejection can be varied Needless to soy, these are only two ascpec of immensely physiological situation. It can thus be concluded that pulsatile ow can never sieelete the dynamic physiology of the heart. B were used as a media for valve testing: water and 42% u in water. The vast ma4crity of workers in this field used water, because it is much easier to work with water, an only a small driving power is neoeasary to circulate ler volisses (Timis et alb, 1964.). Ca,ycerol solution was used because it has nearly the same viscosity as blood. Sample and his colleague claimed that the results of testing obtained by the use of glycerol are more accurate. • Cu the other hand it has been shore that the visoosity of a fluid has no effect on its flow in orifioes (53intooh et al, 1963); therefore 120

tests using water should give the same results Isolation or blood, Kesdi et al (196) eattme Starr-Edwards prosthesis in the pulse duplicator using waterthe touting medium. They also estimated the resistance of the same valve in humans by catheterisation studies after valve replacement, The

valve resistance in both vas closely similar*, These findings further prove that the resultsof testing prostheses in the pulse duplicator using water as the testing medium are applicable to the

ow volumes o be tested must he rate of blood flow across t valve iu the heart rmoderate exercise. cardiao valve is a function of both cardiac output and the fin period (i*e. ejection phase or diastolic, tilling phase). Tbus the mitre' valve flow ranges between 9 litres/min during rest and 80 litres/Min* during mrimAne0 exercise* Similar calculations for the aortic valve give flows ranging frma18, litres/min* during rest to 30 litles/ein ebarin.g soden, exercise (2) Turbullece: oessive turbulence reduoea the forward flow, ate3 inc ses red cell destruetion (resulting in haemolysis, anaemia and jaundice). In addition, the fluid la nearly stagnant in areas of severe tmxbulence„ so tMrembosis is liable to occur (Cartwright et al, 1903), Turbulence is tested by observing the behaviour of multiple tiny particles in the flow stream* The methods usually used tires (1)- Five Methods: Various materials* mast commonly indian inlet sere proxi. imal.tothe-valve and their behaviour-studied either by ttue naked eye or by high speed cinematographic: recording. Temple et 1964 used this method and noted. that if the Mammas laminar, tie`ilyemoved as one mass but if it was turbulent, cross currents paused the dye to diffuse•rapidly throughout the circumference of the. stream. (2) Air DubbleJletho4: This method consists of observingthe behaviour of small air bubbles introltUced in the flow stem proximal to thevalveo The bubbles caw be observed -either. visually or by pine film. Each bubble iss - a distinct entity and the method is much easier anti:more informalive than the dye - method (3)%tun]. votkloasi

Leyse et al (1961) Injected' latez particl.ea preximal to the valve and then exposed the particles to birefringent ligit. pith the use of a polaroid screen they ware able to show patterns of particle movement. A similar method was used by Davey et al (1966) for testing the pulsatile flow pattern in the asellof.•Cutter valve. These methods are very useful but need specialisedapparatus and personnel.

Two things must be noted by each method: the site of turbulence and i.ts degree, The prosthetic valve designs can be altered and turbulence tests repeated in order to arrive at a desi& that causes little or no turbulenoso 122

(3) Comaetelcel Cempetenoe is beet tested in nnimo experimental, It ate, however, be tested in the pulse duplicator by collecting any back.mflow and measuring it or by injecting a dye distal to the valve and observing whether it escapes to the proximal alio efithe valve,

19FWVCAL giAllhq1WSTICSI (1) Ommdpalad Several methods were used to estimate t* `opg and el stag time: (a) l'rsssus;eAaaurementt

Measurement of pressure proximal and distal to the vs simulated ventricular action may give an idea of the valve movement.

Delay in valve closure may be manifested by trent:Ansi= or a pressure rise from the s4mnlated ventricle to the simulated atrium during early Delay in valve opening may be movofested by the drop of pressure in the simulated ventricular chamber below that in the simulated atrial ahamter during early diastole,. The exaot time of opening and classing of the valve can be monitored simultaneously by means of reword. ing the valve opening and closing sounds by a phonocardiograms The period of time between crossing of the simulated atrial and ventricular pressure curves and the inscription of the sounds of valve closure or opening is the mechanical lags (b) CtnematopFtehio Methqd: Consists of high speed eine recording of the valve in ac on in the pulse duplicator (1500 exposures/minute were used by Sarnoft). Viith this method the time of the valve opening and Closure can be ccl

colated with au accuracy ire Mai

The above two metluxis are .ou The velocity of movem t of the mechanism will depeni in the On thr footers s the driving fem, the forterd resistance and the inertial

i) The driving force (i*ei the ventricular force) dope on

the total energy output .and. the 'rate of pr seure rise, both of which, in turn depend on the norocartlial strength and the enaktiastolic fume. it) The forward resistance depends on the diastolic pressure in the ease of.aortic prosthesis) and the visoosity se the Iner is very changeable and depezde on the heart rate and various other things* iii) The inertial lag ty of the rmohanism and that cif the 1)1

West of these fasters are highly changeable in the no heart

under physiological oonditions (ancl in the patients with a L fib- on, they change from beat to beat),

however sophisticated, can ohange all these parameters in way that

they change in the human heart beat way to test the, valve Imement is in Anhui, or human he er

(2) Jamiclullar The heart rate lies between 60 90 beats per minute, Efre* about 40 million beats/year* If the valve is designed to stani 20 years use, then it must stand much more than 800 million beats as the heart rate frequently rises over the average of 70/minute* Quinton et al (i981) estimated the minimum requirenamts as 2 billion beats.

-124 ..

The strength or materie .a under fatigue atrarns often both on the mpenitude of the stress and Via rate its devd2.opaant (dp/dt) (Marx et el 1959), For ball.and-oage valves an acoelerated fatigue pump (1800 3600 croles/Minute) vas doeigned by nenY authors (Quinton et al, 1961; ler, ,1901). In this devise the ball was fixed, to a reeriprooatin made to hit a ring vith a specified,

hat the testing glade the -win to full-cloeedpositions at a rapid cal without imposing oempletaly unrealistic easea on the t 1963)« 11s t ball oft t rrEanarde and spins at stresa be distributed on the whole of its area, In the test theball is rived ana the area receiving e pressure is always the This (seating area) vas calcul tad =around to be

1/7 e total surfaoe area of the tell So, a test that lasts the equivalent of one year will equal normal etre& in the heart for 7 years. fay these two methods (sooelengatea fatigue te tins and rimed seating) it was possible to test the ball of Starr4Idwards valve the equivalent of 42 years of body action and it showed ensigns of wear (Lillehei, 1963). Yet, in human beings the same ball Showed Changes of gear after only 513: months of use (Masa 1965). This egein stresses the fact that the nature of the surrounatagmedium cud the rate of pressure change in the heart oar, be of critical importance in determining the endurance of the mechanism. In testing discoid, meniscus or Dammeremith velvets, in which the mechanisms do not spin l25 or move at random a much longer rice teat Testing the flap and sleeve much the changing flex pattern and varying a of the cardiac valves preclude oorrelation between stress pattern and the durability expect- anc7 even it the flex life of various materials are known (arx et al, 1959).

Valves rted in en3le. Dogs and calves are us The resistance of the valve to blood flow a be tes ted rising the netee, and measuring the cardiac output the period and the pressure grsdient across the Frtifioie1 valve. This an be repeated after exercising the animal. The lag phase during valve opening and closure can be determine& by one of three metheass (1) Phonocardiorrphic Method s

In the case of the aortic pros the valve op be detected by the ejection Clicks and in the case of ritral prosthesis by the opening snap. The artificial mitral valve closure is seen as the first heart sound (s1) ana artificial aortic valve closure is seen as the second heart sound. The intervals Q.4, SI to ejection click, and emend sound to valve opening click depend part],y on the valve inertia and can be taken to measure it. (2) Ansiocar#ioerachic Methqk High speed tine film of the ar tifi.cial valve action lead to A1;

12640 visualisation or the valve movement. This onn be done either injec Ling a radio-opaque material or by using a valve with a radio- opaque medn.anims (there in a Stere*Edeards valve available with a radio- opaque ball), The speed e film determines the limits of error al' this method (3) Ultrasonic This is the ideal m of an ultrasonio beam one soon tocote the valve cusp o its aocoustio impedance is different from that.. of the surrounding gauss)# The movement of the mechanism can be easily seen and its extent meaeured, Tho time needed for the valve to reach the full-open or full-closed position can be found In addition, this method will detect whether there is nay hindrance to the full movo:ent of the mechanism. Ultrasonic testing techniques sere applied to the Starr Edwards valve by Gimenes et el (1945). -127 •

or ITAMP2SLT,r11 VALVE .PERFORL.

to Caere deni a tics of the different varieties of the Ituemmanith velvet (1) To test the hydraulic characteristics of the valves (2) To test the hytraulic performanoe of the ringalcme and to estimate the resistance offered by the trap-door to fluid flow. (3) To test the efteot of varying e distexioe between the trap-door and the ring on the hydraulic performance of the valve.

CO To test tlm,effoot of Changing bete° the trap- door and tie ring on the hydraulic perfor nce the valve. (5) To determine the inertia of the valve during opening end closing.

(6) To test the degree and pattern of in the fluid

stream produeed by passage through at different flow rates. : (7) To study the sequence of valve opening and elosing by l speed cinematography. GPMAL EXPERIMNT4 Ur: Yelves: All aims of the three varieties of the traerneranith valve 'Jere used. 128

Testpr Gaper es of testing chamber wore u moan yes strai th a uniform diameter, end expanding (FSg. . Both 19 tubes were made of pol,ymethyl methmerylate (Perspex). The valves wore placed in the expanding tube no that the ampamsitiness on the distal side of the valve, in order to simulate the expansion of the left ventricular outflow tract which is supposed to receive blood from the valve. Pressure was recorded from the centre ef the stream prom-. imal and distal to the valve by means of curved side tubes which reacled to the centre of the tube. Their curvature wits adjusted 80 that their orifices faced the direction of the stream, Pressure ?Vaadrem!=nt: The aide tubes were come means cf lon pressure tubing to two "U.E.P." transducers and from these "N.E.P ft amplifiers. Then the amplified pressure signals were monitored on an oscilloscope and recorded on photographic paper at speeds of 25 or 80 mm/Second. Valve ViountinN. The artificial valves were placed in the apace betcoc n the narrow and expanded parts of the testing chamber, using interchangeable silicon rubber mountinepieoes. The valves were changed by unscrewing the two parts of the tube from each other and inserting another valve with its mounting piece. Pulse Dynlicationt

Use was ma's of the pulse duplicator designed by W. I. K. R. Manillan (1955) by his kind. permission. The general plan of the pulse - 129 -

Fig. 19 The Testing Chamber

dupLi.cator is given in

A large tank containing water or any o uid le continuous now pump and this leads to two maguetie sole valves which control the pulsatile flow. use valves lead to thet Meeting chamber and. to the valves to be tested, after passing thrrPael a flaw irol regulator Fluid owning from The testing chamber is allowed. to go to a system composed of an elastic tube and an air clamber (described by Knowlton and Starling 1912)0 *Lich emulates the peri. pheral resistance Finally the fluid returns to the tank via a rot emeter Whirl measures the rate of fluid flow. A control panel ellows variation of the continuous flow rate from 0 to 27 Litres/minute and the interrupted 0 to 3.2 litres/minute The pulse rate ova the duration of watole and Oiantole eau be by the mametio solenoid valves. mow PP pffintaum, CO To Test Iralw The testing chamber which the pressure vas measured proximal a distal tv thevalves were

on the 1302130 level in relction to the horizontal plane and a IMO level as the transducers. ( using the expanded tube, it found that there was a pressure difference between the prozeima3. and distal pcx'ts of the chamber even before placing my valves in it, because of the varying velocity of the fluid in the narrow and thc expanded, parts.

To test this, the pressure gradient across the tube at rater flow rates -131-

Peripheral Resistance Control

Testing Flowmeter Chamber Flow Control Solenoidl Valves x

Continuous Flow Pump Water Tank Fig. 20 The McMillan Pulse Duplicator .132 .

frem 1 to 27 litres/minute were measured at one litre increments and a curve of the flow pressure relationship of the tube was constructed (Fib;. 21 ). The valve was then mounted in the teating.efiamber'and the water was allowed to flow through the valves at rates starting from one litre/minute and increasing by one litre per minute increments until a flow rate of 27 litres/minute was reached. The pressure gradient across the valve was measured at each level of water flow. The gradient across the tube was then subtracted from the gradient across the tube With the valies the difference being the true gradient caused by the resistance of the prosthesis alone. (2) To '.hest the lydraulieTerformarpe of the Rinqk Alone:and:to BetliRate the Resistance of the 'rap-doors

M attempt was made to demonstrate the resistance ,to flow offered by the valve ring alone, and that offered by the trap-door alone, and, to 404"Inime.the 'relative importance of each in creating the pressure gradient.40004.thelmlve. :Per this the traP.doore:were*moved from all the:yelves and the rings alone ware tested for their hydraulic characteristics in the same way' as in the case of the assembled pros• theeett and over a range of fluid flow from 1 to 27 litres/tinute. 13) To Test the Effeot of Varying the Distance between the Trapdoor and the Ring on Resistance to Acid Flow: Valve rings of 1.75. and 2.00 cm. internal diameter were used.

These:two rings were chosen becaufle of the high resistance they offered to flow, therefore any change induced in the resistance by a change in the distance between the ring and the mechanism sins-- easily -133-

10

NMI

9

Hg 8 7 MIR /mm

NT 6 IE 5 RAD

=In

G 4 RE U

2 Imn RESS P 1 !lilt 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 FLOW IN LITRES /min. Fig . 21

The flow—pressure relationship of the testing chamber without the valve me m another one everiment. consisted of a lenticular trap-door with three equidistant holes drilled in it. Into theee were fitted three to wires whose ends were bent outwards and which acted as the "legs for suspemling the

troll*Ado (Fie.22 ) method it was possible to the distance between no the ring IsisagY by Nabin wires in either direction thrau their hulas. =de to flow through the valve and the distance between the disc a the ringwas increased by increments of one millimetre while the pressure gradient across the valve was measured at each distant*. A constant rate or water flow of 25 litres/minute was used.

(Zr) NA Th° Mtet or ,vet t /PM Ixt.%mil um Pim a the TrEP216V Pn theleilAPten92 of the V471 V .ens The prosthesis with the modified mechanism (described above) ens used as in the previous experiment, but one side of the trapodoor was kept at a constant position and the other was moved away from the ring by means of lengthening the wires that suspend this side from the ring. Tater was then allowed to flow through the valve at a constant rate of 25 litres/blunt° end the angle vas varied (5) To Study the Ifortl.a of tht Valve Nriptt ta,oeure,ant Ooenipes The following hydraulics system was designed for this purpose. A tank full of water (u) was placed at a heidat of 150 on. above the level of the valve and connected by tubing to one side (the venttioultm'side) of the testing chamber (V) which oontained the valve. The other -135-

Fig. 22 Modified Hammersmith valve with a telescopic mechanism

Testing Chamber

Three Fig. 23 Way Tap hydrailic system for measuring the Hammersmith valve inertia during opening and closing U - high water tank L.- low water tank A - simulated atrial side of the testing chamber V - simulated ventricular side of the testing chamber

trial) sift of cheeber (A) vas oanneoted to another smal con- tainer that was kept at a height of 15 om ale valve Pressure

tracings were recorded from the proeiltal sides of the valve.

A three my tap interrupted the pathway betslee higher water cans.

tainer and the testing chamber. By turning a water pressure of nearly 110 mm Hs was suddenly transmitted the ventricular

Bide of the valve, and the valve vas imTedistely close turning

the tap off, the pressure in the simulated ventrioular r dropped .imcediately and the pressure transmitted to theatrial chamberfrom the lower reservoirliper sated unopposed on the atriel,side of the valve and opened it. i my delay in the closure or the .valve was recorded on the pulse wave as a rise in the simulated atrial pressure simultaneous with, and equal to the rift in the emeleted ventricular pressUre. if atrial the valve closed, . immediately,,, .. no ....pressure vas transmitted to the side* The duration and the degree of the rise of the simulated vent.. riou ran pressure van a measure of the inertia of valve closure, is rrlp, if the prosoure dropped in the ventricular side, for any period of tins, below that in the proximal (atrial) aide, it meant that during this period the valve failed to open in spite of the pressure drop. This pressure drop and the period of tine during which it occurred were a manure or the inertia of valve opening. This experiment vas per. forced on two wives: nark II, 2.25 cm. and nark III, 2.5 cm. internal diameter. (6) To Est the plivr ana Vie' Pattern of Turbulence Auld StrIsmm Artier Passing Throu.sh the Valves Igor this purpose two methods were useds ,. 137 -

{a) Iindisin,D*11 In this case the valve was in a transparent tins ohs:Ober and fluid was allowed to flow thrau it in either a continuous or interrupted stream. The ohm positioned vertically so that the fluid flow was directly upwards The rats of continuous flow varied. from one, to 25 litres/minute A oval amount of indica ink emulsion was introduced into the centre of the Ube below the valve by a special tube and allowed, to ascend with the fluid. Ita behaviour was then observed by the naked eye both above end below the valve. (b) Dupble Vethode It was soon discovered that t gave tan dea of the turbulence, was ter a new method was devised to it the precision enoe could be assessed. The pulse duplicator in the previous emp laenta with the fluid flowing in the tube t the valve vertically upwards at rate varying from 1 to 25 litres/minute of con. us flow and 1 to 12 litres/Minute peak interrupted flow.. A of smell air bubTles vas introduced in the centre of the etre below the valve at a constant rate and the behaviour of the bubbles both above and below the valve was recorded on a pine film. The air bubbles tended to pass upwards due to their low speoific gravity and, any interference or deviation from this straight upward *puree was coneldered abnormal and induoed by the valve itself. The advantage of this method was that each bubble was alveys distinctly seen as a separate entity, varied to test their effect on valve movements The films sea projected on Tage-Arno 35 taxa projeoter t variable rates in order the details of valve movements each frame porsieted fc cocoa, the time of valvo movement vas calculated and compared vith those Obtol

Piga 24 tO30 dive the pressure gradiont se thea rent s of the three varieties of :be' lammer a at various levela of fluid flews Andkvaise following.

(1) The hydraulic performance.e the t'a II valve vas better than that of the nark Is Thate the nark m vas better than nark 11s (Fig. 30). (2) The improvement of performance ve :ore apparent at high flov rates. This is due to the parabolic relation iip'betveen floe and the pressure gradients (3) The Lwaraulic characteristics of the three prosthetic valVes oonformed to those expected from a typical orifice, Les flew- pressure curves were parabolic,

00 The pressure gradients cessary for effecting comparable - 139 -

22 \MI 20 Mark 12.25 cm I.D.

r

18

Hg. 16 /mm

NT 14

DIE 12 GRA

E 10 R

1=0

SSU 8 E R P 6 MM. 4

II I III 2 6 10 14 18 22 26 30 Fig. 24 FLOW IN LITRES /MINUTE The flow-pressure relationship of the Mark I Hammersmith valve (internal orifice diameter 2.25 cm) The flow-pressurerelationship oftheMarkIIHammersmithvalve T

(internal orifice diameter1.75 cm) IEN PRESSURE GRAD /mm Hg. 2 . 1 44 24 30 40 20 36 28 16 12 8 MEM Mark II1.75cmI.O. 6 1014182226 30 1 FLOW INLITRES /MINUTE

- 140 1

1

1

1

.

i

1 20 18 _ Mark II 200 cm. I.D.

E 16 E. N 14 a 12 Fig. 26 10 The flow-pressure relationship of the a u, u Mark II Hammersmith LW valve (2.00 am. EE 6 internal orifice diameter) 4 2

2 6 10 14 18 22 26 30 FLOW IN LITRES/MINUTE 20 Mark II 2.25 cm. I.D. 18 16 14

12 Fig. 27 , 52 10 The flow-pressure CC relationship of the CO 8 Mark II Hammersmith ac valve (2.25 am. C.f) Cf, 6 internal orifice LLI diameter) 1:1- 4 2

11111111 2 6 10 14 18 22 26 30 FLOW IN LITRES /MINUTE

- 14.2 -

14 — Mark III 2.26 cm.1.0. m. 12 10 8 .. 6 “.1 cc 4 - Cn W CC 2 — III 0 1 III 2 6 10 14 18 22 26 30 Fig. 28 FLOW IN LITRES /MINUTE The flow pressure relationship of the Mark III Hammersmith valve (2.26 cm internal orifice diameter)

10

9 Hg

7 T/rnm N 6 • IE D 5 - MARK In Man. I.D. • RA • 6

4 • RE

U 3 SS

E 2

PR • 1 II I 2 4 6 810 1214,16 .18 20.22 24 .26 28 30 Fig. 29 FLOW IN LITRES/min. Tbe flowzpressure relationship of the Mark III Hammersmith valve cm Internal orifice diameter)

- 143 -

22 20 • Mark 1 215 cm. ID. o " II 225cm. ID. 18 • III 2.26 cm. I.D. ten = 16 g E 14

W 12

CC 10

CC (1 cr4 Cr) 6 4

6 10 14 18 22 26 30

Fig. 30 FLOW IN LITRES /MINUTE

Comparison between the hydraulic performance of Mark I, II and III Hammersmith valves to those occurring across the no in the intact human heart in the state and after Oise are given in Table VIII. (5) There was virtually no differenoe in gdratxlic3 perforaanoe between sizes 2.00 and 2.25 of the Mark II valve. The reeults of testing the hydraulic performance of the valve rings alone allowed that with the flow rates used, tbe valve rings of the sloes 2.00, 2.25 and 2.5 cm. internal orifice diameter offered no resist.. awe whatever, to the fluid flow and it was deduced that whatever resist- ance was offered by the whole valve to the flow, was oeuse4 only by the trep400r. Only valve rings of 1.75 am internal orifice diameter offered some resistance to flow, The flovwpressure relation of this ring is shown by the curve in rig. 31. The results of testing the effect of the variation f the distance can the ring and the dire are shown in Pigs,32a and b Analysis he results shows that with the trapoloor very close to the ring

C tanee 2 mm), any increase in this distance caused a crriond drop in the pressure gradient across the valve. This drop became less marked as the trap-door was moved further from the ring. Increasing the dis- tance above 6 mms caused only ama13.changes in the preseure gradient. Practically the some results were obtained with the two valve sixes tested. The experiment testing the effect of varying the angle submitted by the discoid mechanism on the ring showed that increasing this angle caused a small ciango in the pressure gradient.

145

PRRSSIM c114/21T laittrS rAnigcfn_ Itstasurrn YAW* SPLogethr, 117*Xvis

gradient with oast, flow cardiac output) alga Ng.

Narkx (2.25 3.5 /ant II (1.75) 6.0

mark tr (2.00) 3.0 1

mark rt (2.25) 3.0 17•5

Mark XII (2.26) 2.5 124

Mark In (2.5) 1.5 9.5 - 11+6 -

5

Hg 4. m. m in

T 3 N IE D

RA 2_

URE G 1 SS

E • PR 0 10 15 20 25 30 FLOW in LITRES/ MIN. Fig. 31 The flow-pressure relationship of the Mark II Hammersmith valve orifice without trap-door (1.75 cm. internal orifice diameter) 114-7 -

SO. 40.

TO. 35. so. 0 5 50. 25. G

40. 620.

CD 30. CD M.

2°- tai 10. 0. s.

0 I 2 3 4 6 6 7 2 9 10 1 2 3 4 5 6 7 A 9 10 DISTANCE BETWEEN TRAPDOOR AND RING in mm. DISTANCE BETWEEN TRAPDOOR AND RING in mm.

Fig. 32 The effect of change of orifice trap—door distance on the hydraulic performance of (a). 1.75 cm. internal orifice diameter (b) 2.00 cm. internal orifice diameter for a period of about 10 m. 6 n t prassuress separated;

meant that the valve was completely d in a period of 10 m• deo. sure recording for the ?lark valve showed that the inertia of closure was so short as to be considered negligible• The de

0 nine of the Mark II anti III valves V98 neargible• This wan shown that the simulated atrial pressure and the simulated ventric- point where the vent.. and that there was no lag

showed that the air bubbles ascended directly up- wards both below the valve and after passing through it. This was true for flow rates, between one and nine litres/Minute At higher rates it was found that the water and the bubbles were ejected so forcibly from the valve oxit orifice that they first travelled obliquely f'or a short distance hitting the tube wall at the testing chadber end then moved upwards to their destination, At floe rates higher than 15 litres/minute, air bub-bles persistea above the valve for some time indicating the presence of oonsiderable turbulence, The duration or — 149 —

HAMMERSMITH VALVE MOVEMENT

Mark II Mark III

Stimulated Left Ventricular and Left Atrial Pressures On Pulse Duplicator To show that the delay in Hammersmith valve closure is less than 10 M. sec. and the delay in its opening is negligble

Fib. 33 persistence of the air bubble above the valve was directly proportional to thu flow rate above 15 litres/Minute. Repetition of the same experiment on the Mark II 2025 cm valve yielded results similar to these of the Mark II valve. The only difference was that air bubBles started to hit the wall of the testing chamber at a flow of 7 litreatminUte and persistence of the bubbles above the valve started at a'flow rate of 14. Titres/minute, Sequence of Valve Movement; In Wile films* the'- valve opened in two stages (Pig. 34.)4# The first was an:upward'movement of the trap-door as a whole until the legO touched the under surface LT the ring,' The nett. was an oblique movement at the end of which the valve opened ecoentrioally and part of the edge of the trap.door came into contact with the valve ring This sequenoe produces two opening sat ndav one due to the contact, between the lege and the ringo'and the other due to the contact between the trap-door the ring, closure consisted of a single movement (Fig. 54.) in which the trap-door pivoted on the part in contact with the ring and please in one smooth movement One sound resulted. from valve closure as a result of the final contact between the trap-door and the COMMENT: The hydraUlio testing of the Hammersmith prosthesis has shown - that sizes 2.0, 2,25 and 2,5 are all adequate for handling the volumes of blood necessary for the body during rest and moderate exeroises It hem also that the final designs now used are better than the previous

-151. -

I II Immo' P11'7, p

III

IV Fig. 34 V The opening and closure of the Hammersmith valve 4.152 0. ones, fact that there no dii farance be een the performance or the 2.00 and 245 make° it preferable to use the smaller else in the human body, even if' the mitral annulus con aocommodate the larger one, as its small trap-dm:rein maks it better tolerated by the vent- ricle twos due

try er and the Variations of the obliquityof the had. little performance, e appeared distal to the pro8 small flow volumes. However, in these experiments water Accords, ing to Reynolds' Number, turbulence is less likely to occur with fluids of higher viscosity. In addition, the velocity of flow across the mitrel valve during diastole is thought to be slower than the velocity at flow in the testingtemmher in the pulse duplicator. It is thus prdbable that turbeasnoeldll be less pronounced in the heart than in the pulse duplicator, However, it is believed that the degree of turbulence produced by the Hammersmith prosthesis (or by aey eimilar design) mest become too great unaer the high velocity conditions of the aortic valve area. Thus the 1b3meeramith valve is unsuitable for use in aortic) replammeat. The mechanical characteristics of the valve were exoellen Ex* perimaata have shown that both the time and the force required to effect opening or olosure of the prosthesis were very small. The valve took less than 10 milliseoonds to close and. a negligible period of time to 353 opeci, This was significantly Shorter than, figures obtained by experiments on, the balland-cage valve in the pulse duplicator (15 - 20 milliseoondsollarken et al, 1960). It must be realised,: however, that wing to differences of viaoosity between water and blood and also differences between the oharaoteristion of the pulse ' duplicator pump and the left ventricle '(especially in kala 4p/at) tlyp time intervals obtained experimentally may not apply to the valve action in the heart (see page 123). -1540.

and twelve patients were dated postoperatively grit e following ob3eotives inminds ) To analyse the causes postoperative complications. (2) analyse the causes and po to eviate them. examine the hydraulic performance Hammersmith Wheats in the hum heart and compare this performanoe with that obtained on (4.) To measure the inertia of the valve in the he (5) To investigate the effects or .on of the natural mitre" valve apparatus on the moments of the flirt*.

ventrimlar ring. To measure the degree of Improvement in cardiovascular physiology subsequent to valve replacement. To discover the cause of deterioration in three patients after mitral valve replacement. SUBJECTS* alp to the time of writing this thesis 35 patients have had mitre' valve replacement parried out at Harmersmith Hospital. In the first X55 three patients, the - Starvadwardei valve was used, and in the next 32 patients, the Hammersmith mitral prosthesis was.used. Tablet."' gives the details of_the:pa4ants who underwent Hammersmith mitral valve replacement,..,. Fifteen patients are, still alive._ Fourteen living patients had had one•type or other of the Hammersmith-valve. MpRTALITre Two 'of the three patients who hadStarri.Edwardet-mitral valve re-- placement died.. Eighteen patients died afterr- Hammeramith mitral halve replacement. The vast Majority. of. these deaths occurred-in the immediate postoperative periodand-before the patients were discharged from the hospital. Only three patients died later.- So, if the patient escaped- the initial postoperative complications he had a very good ohanoe of prolonged survival. POSTOPERATIVE COURSE: Three patients died on the operating table. In one (B.L) the heart never recovered sufficiently to support the circulation after discontinuing perfusion despite 5,5 hours of intensive resuseitation. In the second (I.F.) haemorrhage from multiple sites resulted in left ventricular failure and death. In the third patient (IOW the heart resumed function after cessation of perfUsion, with good cardiac output for a short while, but soon after, the heart began to fail. Cardiac massage was performed but the manipulation resulted in tears of the inferior vena came, left atrium, aorta and finally right atrium. Attempts at controlling the bleeding were unsuccessful and death ensued. In twelve patients death occurred between 36 hours and 15 days 156 •• TABLE /X =Ira AsszesEsT

Valve Es Myths eltaleal assess*

G.0*

A•P• Rh, , 51. A•to At. ? TS. . .F. Rh.. Mt* MS, A/ XI b De C. 46.11. Oat 64. A.F. 13 T. 15 P NOT 64 b 8.R. F« L. 50 10 Deo a I Ita A•P Mad. MS S.M. 26 P Nov 64 II Et b A Pip • Its Gt ‘F Jan 65 lU II b • SSE* AI Z 49 F Feb 65 UI raiin A.F. W.G. 26. F, Pik 65 xrt min A.F. Se,' MS. 51. MI•Mild At Lao 48 I Farb 65 III lb SA' Pap« easels syndrome L,Jo 43 P. Feb 65 I/I /X b Sem Rho la S el« 38.1. Mar 65 ra It b A .F. Sen. AI, TI• JeCo 53.1 air 65 XX/ 32 a A 0F0 seer. IC At Salo 4 IP Mar 65 In U1/E A•F. UV la • TI. AI. II 14 F Apr 65 m U b A.F. Rupt.chords* B.B. 57 F May 65 DI la a A.?. Rupt. °bards*

157 TABLE

Date Valve Rhythm ClknioPI assess. use

- ,A.410 ken. TI. A44 43,P 5 In II b A.F. NITRE (ms) TI. Vii,Eff 41 Juno 65 ill xx a solo Ries4 NSA. MI D.N. 43 ,M Oot 65 I1r II 0 p.c., 43,11 Oot 65 II lb A.A. Nev. 1.8 P Oot 65 A.!. Se* 1110 TI .

,143,t 53 P Nov 65 b AO NI:t NS' TI 50 Nov 65 II a AO, Nov. mr.lioa. AI

Nov 65 In

A 17 ,131 Deo 65 III S.R.

581, rob 66 III ♦ shoran. after the operation. (M.G.) hepatic failure, and severe haemorrhage ftrom incidental peptic ulcer were responsible for death. Another patios) had a satisfactory course for four days after the operation; then gulden loss of oonaeousnees and con. vasions occurred, end cerebral embolism vae diagnosed« This tins followed by two. attacks of ventricular fibrillation an death. The rest of the patieata had a progreseive drop in cardiac; output preaeure postoperatively resulting in poor urine output and patienta complete Snuggle. h. variable degree of haemolytic and jalmdice tailored. Progresaive deteccioration of their aonditione continued despite resuscitative measures. In tee patiente (La and 3..C.) the peripheral circulation woe so poor that gangrene or the extremities ooeurred. Analyes of blood electrolytes use Lin acidosis QC the three late deaths patient died 16 months after valve

memento from maasive cerebral 6mboliapa: The second patient from left sided heart failure Oa pulmonazy oedemas lio data are available regarding the mode of death of the third patient.

POST MORTEST nDIMS Thirteen of the deoeased were suWooted to poet mortars examination. A summary of the findings is given in Table X. It will be noted that at autopsy the prosthesis vas almost alegys found to be properly placed and free to open and dose. Only one patient had faulty valve insertion that could account. for the fatal 1'leIIIe •. Death val... foIIltda ~a1a!a ot.her Yal.. J1eu't ft. P..n RaIol. - ~at..GP. aDI.wJ.\V Left Atr.ltII· les101Ja 8U. ' s.n. , ....,. - 620 __.ftbft8ia Per.lWl1~ - D.C .. 11 .S8S D1ft&1 4ebls08llOll - L.P. n lfonIr4 811gbt AS I..? 11 1'IeftIa1 VesetaUoDa - .'aorta :r.P. Table Bezrra1 - ,- A~ ••G. , 1foIa1. - QtO HoJsia1. -:LB. 2 1foma1 - '. 480 JfoftIa1 L.J. 7 Sa1wa1",.ahe1e Pl'8_' - 485 lfoJrlla1 B.L 6 JforML fNt*'It 775 1mbl bN!Jd.Dg 5Jl..LV &.,_ 1l.L 'rabl. !kmDB1 • £ .1fGl'ma1 A." 3 E'oJ:'Id - AS.AI.TI Aboess LV 1J811 B.Jt. 15 lJor.m81 - 745 1fOftIB1 D.N~ 5 JlcmII1 750 I(vo. w. - septum. lbto. fllbro81s

• ~"" •

outcome. .tint (1•440 th the proper place tha trap•ftor was ern:awed be valve and a eurgioan iniuoed shelf of tissue tmderneath which measured 2.6 cm. in length. The trap-door could be fermi outside the 0410 by pressure Troduoin a °lick .So the orifice of the valve (and tonsequentiy the nit ra blood f Lawn most have been severely limited. AntemorteM thrombus was found in tho left atrium and exterul4ng to the valve ring in cpatients. In one patient (D.C.) two very all. deli s to re detected be teem the sewing cellar of the pro valve annulus. another patient (DA.) an infarction o the interventrictilar septum the anterior wall.Of the right ventricle was deteeted. 0 LLOWAR:

patients we up teem

a few weeks 20 months. Clin cal improvement and in in the raise tolerenoe was notioed in all but 3 patients of these a dehiscence between the valve sewing oollarand the mitral ulus was diagnosed and later repaired. Their haemodynamie end angioeardiegraphio findings will be described later. The third patient (raft) Id persistent symptoms and signs of high left atrial pressure and pulmonary venous eengestion. Investigations showed faulty positioning or the valve. Her haemodynamic and eine- angiocardiographic findimzs will be discussed later. Peripheral embolic phenomena were noted inii:spatients. IMEMODYTIAMIC tiram$ t"

All the patients were submittod to patheterieetion before the

operation and twelve un t haer studies after the vel replacement. The postoperative investications wore performed from 2 . 25 months after the operation. Ali twelve patients were submitted to right heart catheterisation. -In ,air patients trans-coital catheter- isation was peeformad with direct measurement of the pressure in the loft atrium. The loot ventr'.touler diastolic( pressure was measure in seven patients by retroLwade left ventricular oath terisatione In order to estieate the hydraulio pertor woo of the ranmersmith valves in the hem heart, thefollowing procedure tee planned. The mean pressure gradient across the tral prosthesis was estimated

y p try of tie area enclosed betmeen the loft atrlal pressure curv-n and the left ventrioular pressure curios dvrine diautole. The cardiac output wtvi measie-ed simult neously eitla immediately after the measurement of the ant by means of dye dilution ourvez. The diastolic flow period was measured from he phonocardloGrams recorded at the same time az the inscription of the dye curves. This . period seas taken as the interval between the opening sound of Jin mitral prosthesis and the next proethetio valve &enure round. (i.e. eon component or the first hoart sound). The true flow through the procthesio during clientele was oaiculated from the formula: Nitral blood flow in litreskin. Ca ciao output -In litres min 7 Diastolic flow period in Beaonds -162 4.

These measurements sated,whenever possible, after provoking an increase in the cardiac output either by exercise or in venous isoprensline drip.

Owing to technical the above could not be performed in each patient and the following alterations could not be avoided

(1) In the first two patients (C.s. cod D.0 ) phonoc were not token simultaneously with the cardiac output eatin anon. Therefore, the nitre, diastolic filling period was estimated from the femoral arfariel pulse Neils and Oarlin• 1951), as the time interval between the dietetic notch of the femoral puim and the start of the pressure rise in the next beat. This period averaged O.62.7 se oo ds in the two patients i.e. 76Z of the wale length. The diastolic period measured by this method inoluded the interval between the second heart sound and the opening click of the prosthesis, during which the prosthesis was closed. The true diastolic flow period for the mitre' prosthesis was probably shorter than the measured one. In the other tens. patients, the mitral diastolic flog period was estimated from the phonocardiograms reoorded simultaneously with the carding) output estimation as described. before. (2) In five patients the average diastolic left ventricular pressure was estimated as 5 en 1Tig (Gorlin and Gorlin, 1951) because their 'left ventricular diastolic pressure oould not be measured. lf, however, there had been any =premise of the left ventricular function in these five patients then the diastolic pressure might have been muoh higher -163 ,. than the predicted value. (3) In sir patients the pulmonary capillary prear, a wasAaken as representative of the true left atrial pressure. (4) In 'ten patients, one of: the catheters useiTormeasuring the pressure gradients awes!) the valves MS als0 uaed for injeoting the indocyanine green dye for the purpose of estimating cardiac output. It wpm there.. fore impossible to measure the mitre' velve'gradient,and.the cardiac output at the same time. 'in these patients the gradient ma measured immediately before end after each dye curve.

(5) in two patients (LB. end1613.)4rOss'leakage around , t e prosthetic valve ring was suepected On clinical grounds and. on catheter data and was proved on angigoardiography and at operation. In both, no attempt was made to calculate the mitrel blood flew. In one patient (?1.B..), whole signs of savers mitre. inoompetence after the operation, the catheter Was introducedfrom the aorta to the left ventricle, to further advancing.the catheter, it passed through a dehiscence between the prosthetic valve ring and the mitral annulus and the tip.enterel the left atriums' This procedure was repeated several tunes rind a wif.hdrawal tracing from:the left atrium to the left ventricle through the dehisoence las obtained each time (rig. 36). The first derivative of the left ventricular pressure pulses was measured mathematically in five patients. OFFIOCitatls in two patients 85% Wimp° was injeoted into the pulmonary artery in doses up to 1.5 ml/kgm body weight. Serial biplane picturee were taken b the II ger 4-ray equipment.. The =pommel; were pro at a rate of 6/aeo. fox, two moot:des then 1,/see for 6 8 *vents The left aide at the heart vas visualised sf ter the Aye had circulated in the lungs► In cam patient the dye injected in..the left atrium through a irens.00ptal catheter. In sip patientL the injection vas redo in the left ventricle and a eine angiocardiogram van made at a speed of 38 f'rivaes/seo. in five of them and 100 frames/deo. in the sixth. The high speed eine angiocardiegsvea was performed in order to ensure a higher degree of aceuraw in the timing of the valve movement aid to determine the inertia of the valve closure and opening. The width of the 'left ventricular outflow tract in the lateral view wan measured in all OUgiocarttiograms in *Jo adequate Ore ifioation at the left ventricle was found.

Cine ang.locardiogrems vertu analysed by making into of sueoessive frame and. analysing the poeition of the valve trep..door in each tracing. Any evident:* of mitral incompetence wan noted and the ate, direction end degree of the rvurgitent stream was reeorded. The orientation of the nemertsvith valve and the direction of its maximal opening was else observed in relation to outflow tract of' the left ventricle. The direction at flow of undiluted blood coating from the left atrium during diastole was also noted. The time needed by the valve to open or close vas calculated by counVxng the number of frames taken during the change from the fulli•open to the full-closed positions end vice versa. ?101MIIIITS OP TIM 7111%1 wings

The movements of the mitrel valve tumulus in eight patients with an . .M 165

intact mitrel valve as ll as in seven patients Whomeet excision

cud replacement of the mitre' valve epparatuo std by‘angtai• cardiography. The patients with intact mitral valved were investigated for heart diseases which wore not expected ts change the mitral valve action or the sequence of ventricular excitation. Vona of the.patients had heart block:or bunille branch bloc& at the time of study. In both e"ttp the movements of the mitral valve' ring wee analysed frame by frame. the case of the eine films, tracings of the whole cardiac &mi,ow es de from each frame and several cardiac males depiotea 'my and later analysed In the case of roll films, to urementa wore made directly from the film. In both cases, the extent and direction of the movement of the rmal or prosthetic valve vines was measured from ftmeavererence points. The tent posterior 'position occupied by the valve rive was taken as tho roforonoe position, and movemente from this position were measured in vtirtimetres.' The atrioventrioular ring movements were than plotted on grap .paperta. gethervath the stmultoneoudky recorded elootrooardiogran By this means, it was possible to analyse the atoloventrioular ring movement , to relate it to tho various stages) of the cardiac cricle. In all measurements, all cardiac cycles produoed by extrasystoles end the first two beats-after the extrawatele mere excluded from the measurements in ardor to avoid any possible effect of the abnormal ventricular contraction or enoitation on the movements of the atria. ventricular ring. RESULTSs Haemodynamio neatness - 166 -

The resultss rf the pre~ and p a ale elrOn in Tables XI and XII.

The reap pulmonary: artery pros ea front au av of

38 mm fig. to an : average of 30 mm ng dge pressure dropped from an noose or 23.2 mm Ng to an average of 20 mm Hs. The cardiac) output increassc from a moon cf 4.7 litres/minute to a noon of 54.uties/ minute The pulmonary arteriolar resietance dropped from a trim to of 3.4 units to-a mean of 2,6 units, 'The mean left atrial pressure vies 14.2 I. g. after the operation. Pig. 35)•

in nine postoperative tracings, the, pulmonary vedge pram VMS norrol (Pig« 41 )4, In two patients olio had alinical and baemodynamio evidenoe moderately severe mitred. incompetenco !dab *vt laves vore found in the let atrivi tracings together with rapid spent CP16.36 &37 One patient (I1,1,.) had a hiel loft atrial pressure and a large end•• diastolic gradient bets een the left at and the lert ventricle (p4,84)4.2). The restate of analysis of the hydraulic function of the nammeasssith valve in humus beings (TableXIII) had been superimposed on the valve performanoe ourvea in t pulses duplicator (Figs,38 and 39 and 40). The namnerasith valve closure sound was inscribd about 10 rdili- seoonds after the crossing of the left atria and left ventricular

64 pressure elmves, so the delay in prosthetic valve closure was al out /0 m. Geo, The openin, sound of the valve was inscribed about 5 10 m. sec after the crossing of the left atrial and left ventricular preeauro curves. This mcmls eat the lag phase in valve opening vas less than

10 El. see. (Pig. La). .~.tLt 1f@I!2t"4f~rgc Bi£-S D pABs !Il9J!LBJ.'lWt YALB ~ Pati-.t RA ~ .RVpN8SUI'e PA p....e:sure PCP presSUN .LV pNsau:re PAR. co mm Frs ,. US m liB - Bg milt IIg tmlts l1tres/uda Pbaaio' aIen Huud.o Jrean PhNd.o flerm B.B. 12/; 8)/&42 15IJS 5' 65/20 32 340/0-30 4.7 4.7 Ln. 18IJ4 16 1OS/J., 110/10. 80 - 42 - 8.2 4.6 D.C. G/2 4 110/01\. 45/29 28/22 23 15017/5 2.1 4.8 F.D. ... 12 3O/G") 20/10 ." .. 10 143/19 1.5 S.1 J.P., 8/S , SOl' 50/20 l'30 'All? 19 1'210 3.4- '.2 La.. 13/8; 12 481b/1 53/22 ",. :JtIiJ 20 ~, 2.8 5.0 P.L. • 12 .s2/0/i.2 62/)0. 39. 3J/J4 19 100/5/20 l,.., 4.7 S.Rl - 14 S6/J.o S6/2S 37 38!J.S· 20 ~7 2.' '.7 c.s. u/S 7 40/1 38/27 2S 22tI4 .. 120/10 1.5 s L.W. 7/' 6 "/5-7 3St~ IS 2O/JJ 16 .. 2.' '.5 v.w. nl3 5 6S/01s $/27 ",.. J1,I.I4 31 90/.1.&/27 3J.. ,.8

Av. meaD .9.7 37.9 0.2 ,.1,. 4.7

I .....~ • TABLE XII

litiEMOD=AMIC FINDINGS IN PATIENTS AFTER_ M/TRAL VALVE REPIACENEET

Patient BA pressure RV pressure PA pros PCP pressure LV pressuze PAR Lk pressure CO tin Hg ein lig . sin fig me fig ins Fig units inn fig L/M Moon Mean Phasic Mean Phasic 'Moan B.B. 12 es/05 55 42/25 31 345/0/17 6.1 :r. - 3.9 13 95/5/15 60 70/5 37 105/5/0 4,450:45 30 .5.2 D.C. 38/6/8 30 2040 15 i 2.9 , 5.1 F.D. 22 1.1 . 18/9 12 9.4 J.F. 12 . . 'I4-19/10-3512 4.1 I4 45/5/8 35 30/21 1.9 4.6 F.L. 7.5 50/5/10 25 27/19 . 22 ' 1294 2 146 . 10 30"// 20 15-20/8-1012 .. . ,2.3 12.5 3315 C. 7 35/2/7 20 18/%0 ' 21 . 1.5 5.7 A.T. 3 35/0/$ 22 114/0/1.0 Z.5 10/6 II 7.4 7 37/0/7 27 97/3/10. 2.6 - 1140- 13 5.5 V.L. 13 8/6 7 105/0/5 1.5 7/3 5 4.0 Av, Mean 10.1 30 20 2.6 14.2 5.1

TABLE pill HAIR SMITH VALVE HYDRAULICS

Patient Heart rate Cycle 1 tone period C.O. LA (a) Mitral blood Valve a.aect 111.1100 % P.C.P. flow 3 gradient

D.C. 80 750 610 81 5.16 15 (Pa) 6.9 10 II 2.25 R.G. 160 380 125 33 7.04 27 (PCP) 20.5 22 111 2.5 L.P. 91 660 229 34.5 4.1 12 (LA) 11.9 3.3 ix 2.00 F.L. 102 500 176 35.05 3.55 22 (PCP) 10.05 28 I/ 2.25 S.M. 64 940 380 4.0.5 3.47 12.5 (LA) 8.5 7.5 ix 2.25 C. S. 65 920 625 68 6.1 . 11 (PCP) 9 6 rE 2.25 80 750 345 4.6 4.0 8.7 1.9 ix 2.25 P.D. 98 611 260 45.5 9.4 12 (LA) 20.5 III 20.6 12.0 4.6 xxx 2.00 N.WO 81 740 340 46 5.5 81 740 345 46.5 8.4 18.2 10.7 128 470 235 50 3D.2 20.14. 12.8 III 2.00 A.T. 88 681 ,277 42 7.4 17.6 5.4 127 4.72 208 44 31.5 26.1 8.0 114 528 236 45 Z.5 23.2 7.8

- 170 -

PULMONARY CAPILLARY WEDGE PRESSURE CARDIAC OUTPUT mmH945,_ (mean) LITRES/MINUTE 7 - 40

6 35

30

25

20

2 15

1 10

5 - PRE-OPERATIVE POST-OPERATIVE PRE-OPERATIVE POST-OPERATIVE

PULMONARY ARTERIAL RESISTANCE PULMONARY ARTERY PRESSURE (MEAN) UNITS mm Hg. 9 - BO 8

70 7

60 6 • • 50 - 5

40 4 30 3

20 - 2

10 - 1

PRE-OPERATIVE POST-OPERATIVE PRE-OPERATIVE POST-OPERATIVE e c .Lange in pulmonary artery pressure, pulmonary capillary wedge pressure, cardiac output and pulmonary arteriolar resistance after mitral valve replacement

- 171 -

M • 13-

(

2* m•m•Hg

1#"*.m4,144Falsa**44,414.14#4'444****J"." Fig. 36 ' A withdrawal tracing from the left atrium to the left ventricle through a dehiscence between the sewing collar of the Hammersmith valve and the mitral valve annulus. The left atrial pressure pulse shows high 'v' waves and rapid 'y' descents.

B • B •

M • A• M-F•

L• V •

P•C•P•

Pig. 37 , 1\t

Simultaneous left atrial and left ventricular pressure tracings in a patient with postoperative mitral incompetence. Note the pansystolic murmur in the . 'Hammersmith valve(2.25cm. internal orificediameter) Fig. 39 Thehaemodynamic andhydraulic findingsinthe MarkII • c0 10 00 = 16 • LLI • CC W E —• PRESSUREGR ADIENT/ mm Hg. • 20 —MarkII2.25cmI.D. 12 14 18 18 20 16 14 12 10 4 Q 2 6 1)1 6 8 4 _ MarkII2.00cm1.0. 2 6101418222630 2 610141822 2630 I

I FLOW INLITRES/MINUTE FLOW INLITRES/MINUTE e 0

Findings inPatients 0 0 0 I

0 - 172 I o Findings in Patients (2.00 Fig. 38 diameter). The haemodynamicand hydraulic findingsinthe Mark IIHammersmithvalve am. internal orifice Pig. 4 A PRESSURE GR D1ENT/mm.Hg. 0

The haemodynamicandhydraulicfindings intheMarkIII Hammersmith valve(2.5cm.internalorifice diameter) 22 10 20 6 4 2 MOM

Mark III25cm.ID. oFindings in Patient. 10 1418222630 FLOW INLITRES/MINUTE - 173 • • -174-

V.W.

M.A. M.F.

S2 L.V.

mm Hg L.A.

1\1•401~444***""Vreovwayorontro

Fig. 4.].

Simultaneous left ventricular and left atrial pressure tracings ,and phonocardiogram to show the relation between the sound and pressure waves

irat derivative of the 1 tr p a pulse (dp/dt) was M ed in five patients and 34.5 trim Reno« to 2200 mm lig/seo• with a mean of' 1755

AnfrigverliPtvalkArl In all eases with the Mark II I1 err th valve, the stmt wire placed in the conaavity of the valve ring was clearly eoen in the X-ray and anglocardiograms and gave a good indication of the place of the Ilearzeramith valve and its orientation. In addition, the plastic valve also shoved as a circular translucency around the steel wire in most of the anglocardiograms. In the case of the Lbrk III valve, the eteel wire was replaced by a polypropylene ring which was radio-tranaluoen In the patients who had !ark III Miumneramith valve zeplaoement, only the translucency produced by the valve ring was evident in the angio- cardiogram. The position of the /tamer th valve relative to the eft vent- rioular cavity was best shorn in the lateral views in both the angle- cardiograms and eine films. In these, the Zang azie of' the valve was seen to be nearly vertica with slight forward inclination and nearly parallel to the long axis of the chest (Pig.18 ). The trap-door when properly orientated was only slightly outside the long axis of the left ventrioular. cavity. Its upper tip was =ally directed towards the aortic valve. In the !.P view the valve appeared to be almost parallel with the frontal plane. The width of the left ventricular outflow tract in the lateral view of the angiocardiograms was found to be 3.0

4.5 cra. (mean 3.5 04 in the patients with mitral inoompetence and,

Ite direct was examined in the oine film3« It eas found to be ne rly pointing towards the loft ventricular outflow tract in fiVe patients and at a right angle to it in one. In the latter case (P.L.) the gradient across the valve far in' excess of the one expeoted from the hydraulic testing curves the same blood flow (71 .39 and 42).

acamination of the pattern of the blood flow from the atrium across the Hammersmith valve and into the left ventrioular cavity showed that only the initial gush of blood was directed towards the outflow portion of the left ventricle. The rest et the blood was seen to overflow in the spa batmen the e g e of the trap.door and the left ventricular rails to reach to the main cavity of the left ventaiele• Cb the six patients in whom elm angiocardiograms were done, two had no mitre]. incompetenee. Ito patients had very slight regurgitation which occurred only during a long diastolic period and after extragyetole. In two other patients severe anoomp tenoe was pros evideneed by the marked opaoificaaon of the left atrium after inject radioeopague contrast medium into the left ventricle. The contrast escaped as a jot from the posterior side of the wave in one patient and f'rom its anterior side in the Others suggesting a defect around tie valve ring. The ecoentrioitj of Use jet and its relation to the valve orifice and ring could be easily detected. Me diagnosis of a slipped stitch around the ring was made and later proved at (*oration. -177-

F. L•

Pig. 42 Simultaneous pulmonary capillary wedge pressure and left ventricular pressure to show a big mitral valve gradient in a patient with mal -oriented prosthesis 178

povecentp tho itipetilus

trpieal pattern of the alcveerasnt or -ventricular ring

persons rdth nor .t mitre valve appara is Fig'43 trio-ventrioular rinc.moved slowly forvarde and do ma during systole to reach an extra me enteric) position just prior to the onset of ninetole4. Shortly after opening or,the mitral valve, the atrio- ranVioular ring eterted to move backwards or upwarde /t reached its most posterior position at the.tip or inscription of the QRS eomplex of the electrooaraiogeme, This pattern of move=t was reproducible, in every patient whether in sinus rhythm or in atrial fibrillation. ;hit% indicated t' et otrial cantractione were not implicated in produoing this movement.

t.tovc ,t» of ti atrio-ventrioular seven patients in

VI= the mitr apparatus was excised an need by a Hammersmith

prosthesis were fours to be identical 111 th tho the emerious,group (lag* 43 )e Neither the extent of the moveront nor direction, or its temporal relationship to the elootroeardiogram se effe°tad in any by the excision and replaoement of the mitrel valve, Inc}tine Vapp Action,

Two frames were unually taken the .th valve to change

from the rUlly-olosed to the fully•open po at a film speed of 100 frames/Ceeend# The Change from the rakywiopen to the funy•closed positions also occupied two fremee. It was ocnoluded that the prooesses of valve opening or caesura required 0.01 a 0.02 mooed Fig. 4.3 and theeleotrocardiogrmi The relationbetween themovementsofmitralvalveannulus

MOVEMENT IN mm. T.D. LS. OL

NORMAL MITRALVALVE MITRAL VALVEREPLACEMENT - 179 OMM The atimate test of a prosthetic valve is its performanoe in man. The reatermith wave vas 1m2lantea in 32 patients with gross mitrel valve disease, of tip 14 are still alive, Llving a 3Z mortality, ehich is certainly heavy, Vavertheleigs„ sever- factors !met be takima into consideration. !any of the patients operated• upon °spot:daily the early ones, were in extremes with longstandin, chronicleart failure and high pulmonery vaseulerresistanoes This type or seleotion was essential for neither the results of the operatien, nor the long.term prognosis of prosthetic valves in general, and of the Ikmaseramith valve in particular were hnovn. It ras fa/t initially, that ouch em operation should be advised only for patients in whom the promo eel treatment wao vrgy Grave.

One factor that sedeed to account :Per mc f . the. oaths on the operating table as coexistent aortic incempe Ite, bleodleaked backwards from the sortie valve into the operative dater ti.• tution of cardio-pnlmenery perfusion, and mixed eith eir-eorming froth. Several mechaniame might account for thin fatal outcome in such patients.

The incompetence resulted in low .aortic pressure at the time of perfusion leading to poor coronary filling and myocardial ischeemia. The leak, the frothing and the soot ion mgy have lea to some demo of trauma of the formed elements of the blood end as it was rat urnea bank to the patients, this Craver may have prediepoeed to haemolysis and thrombtais. Sometimes a considerable leak. forced the surgeon to perform aortic alempong for short periods during the performance of the operation and this in turn mere all these prooedures increased perfusion time which m bE a factor for the poor progno Um* noted that hearts with significant associated aortic into term cooed not take over the maintainanoe of the circulation after coming off perfusion. The most serious hasard in patients surviving the operation was the low cardiac output state and electrolyte imbalance. Several patients never acquired adequate cardiac output and developed visceral and peripheral ischaemia loading to oliguria, anuria and even gangrene of the extremities* This syndrome tee often associated with hypokal. aemia and metabolic acidosis* It is possible that hypokaleemia may have played a central part in the whole problem, Itipolcalwamia was usually duo to the preoperative use of intensive diuretic therapy ehich depleted tho body potassium, and the use of digitalis preparations which caused a leak of potassium extraoallularly (Breckenridge and Benton, 1965). More moderate use of together with full knowledge of body exchangeable potassium are therefore, essential before embarking on surgery. The use of plasma potassium was of little value in deteoting hypokalaemia due to its lack of correlation with the body exchangeable potassium, the latter can be measured by isotope techniques. Frequent and obstinate arrhythmias amounting to ventricular fib- rillatian were common after mitral valve replacement, and could be accounted for, at least partly, by the abnormalities in potassium balance. Breckenridge and nontal (1965) suggested the use of rapid injection of small doers of potassium chloride (3 - 5 m. equiv.) intravenously for this nation. Another possible cause of the low cardiac output state commonly after valve replacement may be the of the papillary muscles and the disturbance of the etrio..ventrioular ring movement and left ventricular ejection mibsequent to it The part played by the atriowsentricular ring en in the normal physiology of ventricular ejection was investigated by Rushmer (1956). He ascribed the downwards and forwards movement at the airia..ventrioular ring, which was noted during early phases os systole, to the contraction of the papillary muscles. Lillehei at al (1964) believed that excision of the papillary muscles, chordal tendineam and mitral valve leaflets, usually carried out prior to valve replacement, may interfere with the normal downwards and forwards movement of the ring and hence distueb the normal sequence of ejection. These investigators noticed that replacement of the valve with preservation of the papillary muscles and reduced the incidence of the low cardiac output s in their patients after valve replacement from 4.6% to 0. vie and Kinmoth (i9O) ascribed the atria-ventricular ring .move- meats to the ejection of blood in the aorta causing it to straighten and push the cardiac skeleton (including the mitral ring) downwards and foreards. ixtrapolation of this view leads to the conclusion that excision of the valve apparatus will not significantly alter the physiology of the valve ring, The results of this study showed that the atrio-ventricular ring movements were identical before and after the total excision and, replace.. 183

moat of the mitral valve with a ~ranith prosthesis, the tip re- lationship of these movements to oleatropardi ogram were also not afi'acted by this prooedure. This led to conalusien that excision of the mitrel valve apparatus did not effect the movement of the mitrel valve ring. This study also showed that the first derivatives of the left ventricular pressure pulse (apfat) were within normal limits after mitral valve excision and replacement. These findings indicate that this procedure prObably has no adverse effect on the ventricular contractibility. However, it is possible that preaervations of the papillary muscles and chordas tendineae may improve the cardiac output by some other unidentified mechanism. A more cheerful. story will be noted when we consider the 17 patients who had survived the immediate postoperative period. Fourteen patients are still alive and well, one week to 20 months after replacement. Only three met with serious complioations. Two had incompetence around the ring of the prosthesis due to the slipping of onei stitch which was later repaired. The third patient was found to have aims of prosthetid stenosis Ihich'was found to be due to mal.alignment of the vales in relation to the axis of the left ventricular outflow tract. The remain• ing patients were improved,

taa1yaic of the haemodynamio investigations ye function thawed that: (a) The true continuous flow across the mitral valve per minute was about three times the cardiac output estimated by Fick's method or by dye dilution curves. This was because the diastolic flow period was, in most oases, about one third tae total cycle In, one patient (Rses) for example, the prostbatto.blood flow tae 22 litres/minute, while theeardiee output en only 7.04 litres/minute mei the heart rate was 160/Minute. (b) The higher the z:eart tes a shorter a di etoli0 period relative to the (vele lengths valve flow the cardiac output was greeter at hi (c) The gradients across the valve were the expectedsgradients from the hydraulic testing (P3g.59 ), The previoualsy tient:toned. shortoomines of the catheterise MO-Caere usea could account for at least a part of the discrepancy, one patient (174.) the reason for thedifference was discovered et anciocardioereehy to be the maleerientation of the valve. (11) The mechanics/ cherecteristios of the rammerii.th isive in the heart ere =anent, The opening time tee found to be leas than 10 milliseconds while closing time was usually about 10. milliseconds, Both intervals compare favourably with the natural valve performance Patigue endurance is best asseased fron the fact that the oIdeet valy© has been working in a human heart for 20 months ae far, eith excellent results. Only time will • show the endurance limits of this valve. In angiocardieereme and oino angiocardiograms, the Hammersmith valve was shown to have its lone axis in the direction of the long axis of the left ventricular cavity.. no trapdoor protruded slight ,y in the cavity during diastole,. The decree of protrusion varied 'hetveen 5 and 13 INS (me pace105 ). The average width of the outflow tract of the left . 185 —

Ole Was :Couml to be 3. ve replaCement and 3.0 am. aft valve replacement. considerably in excess or the protrusion of the Hammeramivalve's trap-door. During systole. the 'Wap.door was cloeed and was thus removed from the ventricular cavity and outflow tivot. This el4m4nnted ibility of interference

with myocardial contraotioni or irrita nyouaiidium by am part of the valve. After valve replacement. sixia angiocardiograpby show that the rosthesis was competent. The alight inoompetence notioed during long diastolic it and after extra-systoles was no more than usual for a normal 'teal valve and was of no

(2) estigate the me of each of these sounds it relations to the eve movements and to the haemodynamio

to the Neste of an the v .ve action as demonetwated by the phvn+c.oC To examine the effects of valve repla t n the phases the cardiac wale. describe the change the

study is based on twenty 't a pet valve t. Twenty-one of these had thedr mitrel valve replaced by one o other of the three Hammersmith valves and two patients had their mitral valve replaced by the otarroiEdwards valve. Of those with the Hammersmith valve, one had the Mark I valves seven had the Mark II valve and thirteen had the Mark III valve. Forty patients with aortic valve replacement are also eluded. In all these patients a ball-and-cage valve (the Starr-Edwards valve or the - 187

Mbeevern valve) was u Vest of the recto ere made on N.E.P." phoncoardiographic machine model A 4/2 using a pies:so-electric microphone The machine had three frequency medium and low. sponse

curves of the three bands are z in Pig 44 wore

made on a photographic reoozxler E.E.P.") at a air 80 to/ second, two patients the Elema Catirex 42 LUngograph, direct- writing phonocardiographic machine was instead, with a paper 'peed of 100 mmieecond The electrocardiogram was always recorded simult. aneoudy with the phonocardiogram and used' as a reference tracing. /n sc e patients, the external carotid pulse or the apex cardiogram were also recorded el produced aortic prosthesis and their haemodynamic correlates, 14 patients were studied between 2 and 6 weeks after the operation, by recording the phonocardia0 gram and central aortic pressure simultaneously. The phonocardiograms were recorded by "N.E.P." microphone and amplifier in the usual way. The aortic pressure was recorded through a poXythen catheter introduoed into the ascending aorta from the right brachial artery by a modified Seldinger technique. A G 23AB Statham pressure transducer and a V.E.P." pressure amplifier wore used, and recordings were made at a paper speed of 80 mm/second. The resonant frequency of the whole wet= including the catheter was =endued by attaching it to a pulse wave generator and it was found to be 34 oipss., with a uniform response of

up to 12 c.p.s. 1 1 1 1 1 1 I I I PHONOCARDIOGRAPH AMPLIFIER TYPE. A.642

1011"1.1.-- '0141101441111

41

FILTER POSITION No4.

FILTER POSITION No. S.

FILTER POSITION No S.

FILTER POSITION 14,2.

FILTER POSITION Not. FREQUENCY RESPONSE WITHOUT MICROPHONE AND GALVANOMETER. CONSTANT OUTPUT, VARIABLE INPUT.

I 1 i ili• N 4i° sl ag 0 5N (4 111 a ••4 41) 0 O Fig. 44. The response curves of the FREQUENCY C.P. S. N.E.P. phonocardiographic machine 8 to the tbing and the by Raftery (1965), ducer in the usual to its of the led pre onshipa of the onset vibrationss the delay sure was measured end to be 5 milliseconds from the taming of.the pressure e'Ver'y onship bemoan the sounds produced by the pro es s p a waves wore =awned. All the phonocardiogrephic measureten were made to the nearest $ nilliseoonds with the aid of a pair of calipers and a hand lens. The following measurements were made in the paticnta with mitral replacement, RA interval (2.6artificiel valve el (3) Q*secondheart found interval (t x) (4) Duration of the artificial,velve closure eat (5) Interval from the aortic closure to the opening sound of the prosthetic valve (//,..O.S) (6) Diastolic flop period (interval between t fie prosthetic open.. sang sound and the next closure sound), 90 -.

In the patients aor LVO x at, the following intervals wore measur (1) R.D. interval (2) Qwfirst sound interval (Q4) (3) sertificial valve closure sound interval (Q-II) (4) Q•valve opsn3ng click interval (Q-41) (5) Interval between the first sound aiz the first m ajor valve openinc click (I-C1) (6) Ejection period (interval between t opening' eh Claming sounds of the prosthetic valve. e ejection period was also calculated as a percent r of the total +vole ngth and the nunber of the ejeotion clicks was el noted in each phonocardicgram. The 11-first sound (or Q-mitral valve closure sound) and the Q'soeond soound (or Q-aortic valve closure sound) intervals wore both corrected for the heart rates by dividing them by the square root or the previous interval . MAW FUN9TIO or v The mechanism of produotion of the ,n. click by the ball-and valve and 'their sigaificance wore emperimenUlly.

A krdreulic System UM Co011atrUetha consisting of torn-Miverie sortie valve mounted in a persper tube of uniform diameter. to McMillen pulse duplicator was used to force an-interrupted stream of-rater across the valve simulating the heart pulse. The behaviour of the valve, its method of opening and closing, as veil as the movements of the ball were

noticed and recorded. by a high speed a frames/keoond. During the film exposure, the rite of peso el, as well as the simulated ventrioulcr premium and peripheral resistance. The effects .of these manoeuvres on the flattop of the areficial valve ear* analysed.

otoNoctaDIOGIVIPITY IcITTER CRAP THE FIRST HEART MUM The first heart sound vas aapo of a sews of sapid vthrations

(t artificial valve closure sound) pre by two groups of slow vibrations (Fig.4, ). The central Uncial valve closure) sound consisted usually of two groups of high frequency vibrations (F1846). The first group was usually of Merl amplitude and short duration, but sometimes it attained targs dimensions (Fig.47 ). The second group was of very high amplitude and lemma. 0.033 - 0.111 Same (erithmotio mean 0.07 see). The artificial valve closure sound was preceded by a group of low amplitude, lou frequoncy vibrations whose duration varied between 0.03 second and 0.043 second, and was followed by another series of low frequency vibrationa. The olosmre sound of. the Starr..Edwa valve Consisted txf a aeries of rapid vibrations whioh were of lower frequenoy and of larger amplitude than those of the Eammeramith valve. In our recordings. the Starr- Edwards valve closure sound was not preoeded by slow vibrations like those described by Eultgren end Hubis (1965)4 II ., Tnn moo MRT SOUND; The second heart ssund vas found to be normal in nearly all the - 192 -

J.Fi •

M u. A2 aS. tio

E.C.G. Fig. 45 Phonocardiograms from the mitral and aortic areas after Hammersmith mitral valve replacement, to show'the components of the first heart sound and the valve opening sound. - 193 -

S •T•

Sa OS

A•A• M.P.

M.A. M.F.

Fig. 46 Recordings of the Hammersmith valve sounds from the mitral and aortic areas (medium frequency) to shot the small and large components of the artificial valve closure sound

D • C •

A•A• L•F •

M •A• M• F•

4

Fig. 47, Recordings of the Hammersmith valve sounds from the mitral area (medium frequency) and aortic area (low frequency) to show two large components of the artificial valve closure sound. They also show the change in the valve closure sound after atrial extrasystole. patients studied. In, one patient, a reversed splitting of the second, heart sound was diagnosed because both components of the sound approximated on inspiration. This phenamena was recorded only 24 hours After the valve replacement,

III. ... THE OPENING SOUND:

The opening sound of the Hammersmith valve consisted of one or two groups of very high frequency vibrations, which lasted between 0.023 and 0,0% second' (arithmetic mean of 0.036 second). They were' usually higher in frequency and smaller in amplitude than the valve closure sound.

In the patients with the Starr-Edwards mitral prosthesis the open. ine sound occurred 0,08 eeoond after the second heart sound and oonsisted of a variable, number of high frequency vibrations. IV .0 ADDITIONAL SOUNDS: The fourth sound was recorded in one patient eh:, was in sinus rhythm and whose mitral valve had been replaced with a Hammersmith

Valve.

Diastolic sounds were recorded in both our patients with Starr-I/Wards valves (Pig.48 ). These sounds were analogous to the ejection sounds commonly recorded following the opening of the Stareea4mords aortic prosthesis and. were due to the repetitive bouncing of the ball against the tip of the cage after opening was completed (see pagan and Pig.61).

V MURMURS: A systolic murmur was recorded in the mitral area in 3 patients with the Hammersmith valve (Figs.37 and 49 ), and also in both patients with a Starr-Edwardc mitre/ prosthesis (Fig. 0). PHONOCARDIOGRAPHIC INTERVALS: Table= gives the results of measurements of various intervals - 195 -

S. R. POST-OP.

R A. M.F. M.A. M.F.

Starr Edwards Valve.

Fig. 49

Recordings from the pulmonary Phonocardiogram from the aortic and and mitral areas (medium mitral areas (high frequency) frequency) after Starr-Edwards together with external carotid mitral replacement. It shows pulse tracing after mitral valve the systolic murmurs and the replacement to show a faint systolic diastolic sounds. murmur (S.M.) in the mitral area Patient '!iIan <;1-1 'ueimOOl"ftlGtea. ... ~n 1Ie8n" OOrreeW Mean, n-o.s. ,Itoim~, . :>'lC- .Q-I SI.'c:. :See. Q-1I s ee., Slle... D1aatolo

G.G. O.05S 0.059 ,0.3Oft. 0.)27, 0.060 6Sel D.C. "O.or.:t 0••9 s.a. "·0.'30 0..389' S.L 0.0885 D.C. ,O.oGa O.09If, A.F. O.a, 0.400" A.F. 0.OQ.5 48-3 J.L o.OQ O~0f33. 0.257 0.'" 0.09'f. 48., s.er. 'o.osr. 0.076 0.2Q. 0.367' 0.08 4'+-5 LG. -0.056 0.080" 0.263 O.:seo" 0.077 41.1 A.G. o.or.a 0~Q5S 0..:56' oJt.O' 0.093 ".~ S.L '0.09. 0.091 0.'4& 0.3C1" o.or.a 49.7 J.F. eO.OS! 0.067 0."9 OJ+l5· 0.055 51.7 L.J. O.OS' 0.066 0.248 0.329, O.os J.C. ,'0.059 O.OG3 0.301 0.324- 0.098 51.'56.7 13.2. -0.056 0.061 0.;506 0.325- 0.l26 55.2 J..G. O.~ 0.051 O.m O.:sr.s O.oar.. I.". 'O.om. 0.098 0.350 0.lt17' 0.090 48.'47.$ F.r.. -0.070 0.085 0.321 0.391 SO.?l,. e.s. o.OSG 0.062 0.399 0.426" 0.069 4.9.' S.l!. Chc».o 0.0" 0.28l 0.401 0.071 3$.1 Ln. 0.0715 0.095 0.302 0-'+03 o.067S 4.7.1 D.c. 0.CJt,25 0.057 O.$. O..s. o.uo 4G.4 A.fl. 0.060 0.071 0.3" OA29 0.100 38-, L.Vf. 0.0740 o.os. 0.321 O.3Q,. 0.n6 51.7 I.F. 0.072 0.087 0.291' o•.3St 0.097 56.'

Total. 0.058 0.072 0.)0) 0.376 0.083 49.4 I i .' - 197 -

Preoperative

R-R in 0.829 0.663 X late 0.060 0438 Q-X interval n aeo comet, 0.071 0.072 Q.-Er interval 0.361 ©.303 Q-XI interval ,.3eo (oorreo 0.406 0.376 Etiovelve opening click .oes 0.092 0,083 Diastolic. period ro 50.6 494 - 198 - in the patients with all The mean Q-artifici4 /alve Voayre between 0.0!1.0 "and 0.081 second with en erithmetio mean of 0.058 When this interval was corrected for the heart rate (by dividing by the square root of the R..41 interval). it varied between 0.053 and 0.098 second with a moan of 0.072. second. The mean preoperative Q.first sound interval was 0.06 second before correction for the heart rate, and 0471 second after thia correction. The 0...erto9n/klvaTi sound interval, ranged, ter mi valve re- placement, between 0.246 amend and 0.399 second th a mean of 0.303 second. After correction for the heart rate, it ranged from 0.324 to 0.429 second with a moan of 0.376 second. The mean preoperative Q-second heart sound interval in the same patients was 0.361 second, before correction for the heart rate and 0.106 after correction. The II...valve openineLsol4nd interval or the prosthesis ranged from 0.04 to 0.126 second with a mean of 0.083 second. Recordings Pram four patients before valve replacement Showed that the II-Opening snap interval ranged from 0.059 to 0.12 second with a mean of 0.492 sscand. Met of these patients had predominant antral incompetence The di/Antal° Pii1 D9ri9d (interval from the valve opening sound to the following closure sound) varied between 35.:Vg and 65.1r of the RoR interval. The mean was 4.91.4 • Table XV%tves the mean values of the phonocardiographic intervals in the patients Who survived operation for, a period of six months or Al. 199

pipti Mgt_ =Or 4114 PAT; t)

AMR RAISIFRSEM TRt"'Aron,filtinligPT Pi It. VIM suRinvID OPERATI011 rpugx lams XORX

te eho died early poet- erative period

R-R interval 0.670 0.693 interral ,0,059 0.057 interval , ',see (co 0.075 0.071 Q-It intervel 0.312 0.287 interval. 0.385 0.356 11..valve opening i 0.084 0.475 Diastolic period 48.5 524 more, and in those zho died in the inneate. ve period. The shorter Q.-valve closing sound interval IT-valve opening sound interval 'in the patient 'who died in the early postoperative period

of the tie I i zeramith valves ad with the Starr.-Edwards valve are give VALVE squps AND inutvALs DUDE The coomonest varieties of arrhy

(1) Atrial "Fibrilllatiels The diastolic filling peri During short beats the filling s reduced to a very short time. Table 18 exes the values of the various phonocardiographic inter- vals in patients in sinus rhythm and in patients with atrial fibrillation.

The figures show that in Filii31 tton to the inoreats in heart rate, the Q.-valve closure sound interval, VIOAS shorter and the Il•valve opening sound Ys longer in the fibrillating patients. Both findings could red to indicate a greater degree of mitra.1 obstruction. On the other hand, the Q-valve closure sound interval and the 11..valve opening sound interval could not be correlated to the previous oycle length a point against sigtilloant mitral obstruction. The diastolic filling period tas shorter in the fibrillating patients (48.1, of the E.-R interval as compared with 52.4% of the R-R. interval in patients in sinus rhythm)* PIFAN PHOrfOCARDIDC*Plin ICETRAL REPLACEIDENT RAITERSKITH VAIMS

Mark I Sark II Mark III

interval .'1.sec 0.880 0.671 0.637 Q./ interval 11.3** 0.055 0.057 0.059 Q-X interval sec (eorrootod) 0.059 0.071 0.074 Q..11 interval seo 0.303 0.325 0.290 Q-II interval n:.sec (corrected) 0.327 0.399 0.34 Moral,. opening snap „see 0.060 0.079 0.086 Diastolic period % 654 46.0 50.0 14FIAN PliC600ARDIOGRAPHIC Isnams PASS IN pThUS =TIM ADD MEAL ZEBRAI'ACT ArER UPW4uTP Ian" YAW

Sims Rhythm, Atrial Fibrillation R.R interval sec 0.708 0.656 Q.I interval eec 0.056 0.057 Q-I interval ,,,sec 0.068 0.07‘ Q-II interval , see 0.310 0.303 Q.II interval , eec (corrected) 0.068 0.380 II-valve opening snap r sec 0.082 0.678 Diastolic period % 52.4. 48.3 - 203 -

(2) PxtrasvotOess Usually extrasystoles closed the Has valve, but the diastole of the preceding cycle was shortened or abolished (Pig.%) ). In addition, the configuration of the first sound was usually changed by the extrastystolic beat (Pig. 47 )0 The valve closure sound during extras:rata° was of shorter duration and of higher frequency than the one resulting from a sinus beat. PRCROCARDIOGRAPpf Arm MIMIC VALVE RMACEMPT I m irpsir HEART SOUND: In the majority of patients, the first heart sound consisted of a series of low frequency and low amplitude vibrations starting 0.062 second after the Q wave of the electrocardiogram (ranges 0.033 to 0.096), and lasting 0.084 second (Fig. 51 ). It was usually completely absent in the high frequency recordings (Fig.52 ), and was best recorded in the atrial area in most recordings the central high frequency vibrarn ti ons of the normal first heart sound sere completely lacking. In one patient, first sound could be discovered at all. ants the first, heart sound differed from the above description. In these, it consisted of a series of large vibrations or high frequency well detected in both the high and low frequency record- ings or even better detected in the high frequency recordings (Fig.53). They lasted 04,05 seoond (ranges 0.03 to 0.08 second). in some patients the first sound was separated from the artificial valve opening sound by an interval of about 0.020 second (rig.53 ). In others, both merged into each other so that in the recordings from the mitral -204.

v•w•

M•A• M-F•

-25 .

L•V •

mm Hg

L•A

Fig. 50 Simultaneous left atrial and left ventricular pressure tracing, with phonocardiogram recorded from the mitral area. It shows that the diastolic filling period was abolished by an extrasystole.

— 205 —

•• •

A A ty.lima••• L •F Si CI •-•—••••40++,""—••••••NANtiv...4.4A•w•—w-AA/4.4nes7.1,A"...... AAlie4~...

eiramAmmsy•Weettom.00....0011\moramalmo, Ni\ow...som"....ftwwww....."...meroOoftwoirl000lvaogs

Fig. ]. Phonocardiographic recordings from the mitral area (low frequency) and the aortic area (low frequency) after aortic valve replacement to show the low frequency first heart sound and the high frequency artificial valve opening and closing sounds. -206-

Z • K •

CI 32

A.A. H •F•

M • A • H • F •

OVII.1111111111.11.114kainmsmiaissomov, Pig. 52

High frequency recordings from the aortic and mitral areas to show an absent first heart sound

S • B •

Cl

Fig. 53 Medium frequency record' gs from the aortic and mitral areas to show the high amplitude of the first heart sound (Si). A fourth heart sound (s,) is also seen. 207

area no, distinction between them could be founds The onset of vibra- tions in the mitral area was taken as the start of the first heart sound. II pm SpCONDL, T SOWS In general, two elements of the second heart sound could be reoog- nixed: aortic and pulmonary (Fig,55 )4, The aortic oomponent consisted of a few high frequency vibrations of very high amplitude (Pig, 52). They were brief, lasting 0,01 to 04,04. second. The second (pulmonary) component consisted of one or more low frequency vibrations that followed the prosthetic cloeure sound by a variable interval ranging from 0.02 to 048 second, with a mean of 0,04 seoond, It was devoid of any frequency elements, in contrast with the normal second Pulponary found (Fig,51•) and wee absent from the high frequency recordings. In one patient, the second sound oonaiated of two croups of Vibrations of high frequency end amplitude (Fig's? ), (ise, the aortic and the pill. =ca components were both of high frequency). In two patients reversed splitting of the second heart sound was found. (Fig.56 ). The pulmonary component was usually restricted to the left sternal edge and vas not recorded in the mitral or aortic areas. III - SYSTOLIC SOUNDS: A feature common to all phonocardiograms of patients with sortie valve replacement by the ball-and.dage valve was the presence of a variable number of ejection sounds. In every sinus beat there was at least one sound of very high Ariplitude that followed 'the first sound (14+52 ). This sound (the valve opening click) vas usually very

-208-

P•D• 13•

. P.A. M• F•

NANIsift,04/1.1•••••=01,1100ftaiiill."•••• Fig. 55 Medium frequency Shows the absence of gap between recording from the pulmonary the first heart sound (Si ) and area to show the pulmonary the opening click of the-ball- second sound (p2) and-cage valve (01).

G • S • F• L •

A4k- L • F-

M•A- L •F •

0•10.1"ftwammaraiseimono00".0.4\rirmaiesreaftear0..010 Fig. 56 Fig. 57 Low freqUency (L.P.) recordings High. frequency recording from the from both aortic and mitral pulmonary area and the left sternal area to show reversed splitting edge showing a high frequency of the second heart sound. pulmonary second sound. — 209

brief in duration & of' high frequ It was inscribed suet after the onset of the ride of the aortic pressure pulse curve (Fig. 58). In many cases a much smaller series of two or three vibrations preoeded this main click by a few millieeoonds. They were inscribed simultanw (may with the onset of a pressure rise in the seconding aorta and ascribed to the departure of- the ball from the ring.

In addition a variable nuaher sounds wore elac recorded

in stole and were of high amplitude, high frequency end short duration (Fig. 60 ). They were located at a verieble distance ft au each other. They varied in the same person in two different re pordinge as well as is different parte of the sane recording (Fig. The determinants of these variations were unknown, DYMMIC FUNCTION OF yIR:ITARR0TOWAREG VALVE: Tests in the pulse duplicator showed that the opening of the valve vas acoompanied always by spinning of the balVaround itself at a very high speed. as the ball reached the tip of. the cage, it hit it once, bounsod, and then started to hit the sides of the terminal pert of the cage in a repetitive manner (Fig.6►1 ). The rate and manner or these vibrations varied with the Change in the pulse rate and ejection rate. At higher rates the bill was found to hit the tip of the eagle, then vibrate in its terminal part without touching the sides. At even higher rates, the silage° ball travelled to the tip of the cage *ere it kept a constant position throughout the ejection period without bouncing« At very high rates, the valve either opened partially or did not open at all, presumably due to the mall ejection power of the -210—

J•C•

Six AA WF

AORTA

25

Fig. 8 Fig. 59 Simultaneous aortic pressure and Simultaneous aortic pressure phonocardiogram. The first heart and phonocardiogram to show sound (SI ) is followed by the sound two aortic prosthesis opening producebyr the departure of the ball clicks. (x and x) following the from the artificial valve rin (x). rise of pressure in the aorta. The main valve opening click (C1) follows the rise of pressure in the aorta SO

H • E •

A•A• H •F •

M • A• H • F •

Fig. 60 High frequency recordings from the mitral and aortic areas to show the variable number of artificial valve opening clicks (Cl) R = respiratory noise. - 212 -

I II

III

IV V

Fig. 61 The opening and closure of the ball-and-cage valve mechanioal system at these rate**

IV' - DIASTOLIC. SOUNDS* A third heart pound was recorded the phormardiograma of three patients (Ft& 62). It f011owed the artifice vdtve closure by . 042 to 0.16 second (means 0,14 second) The fourth heart sound was re oorded e mitt # three patients (Pig* 62)* 4u.muMURS: Teo types of murm re (a) Aertio Sveolic Marmurt This was a diminuendo gystolio murmur tit a xted a th high amPli** immediately after the valve opening click and diminished as ejection proceeded. The last third of the ejection period was usually devoid

of MILITIUre (11.0.57 and 64. ),• In some patients the murmur was diamondpehaped with= early peak (Fig. 63)* so the 4 the terminal third of the ejection period was also free of murmurs. The intensity of the, murmur varied directly with the length oaf the preceding eYole (Fig. 65)* (b) Early Diastslic Mure4r:

This was heard in five patients, but wed be recto in one. patient the murmur lasted during the whole of diastole (Fig. 60* OF TUF CAVIAC Cfatt (Table XXX) isometric contracilon (interval between the first heart sound end valve opening click) and ejection times were not precise because the valve opening click e1rs followed ejection of blood into the aortic root by a ehort interval (10m* sec)* This fieure seemed — 214. —

6•13•

A•A• M.F.

M.A. L.F.

•sommmAr...... ,,,argiarogusioiftemeAgara.„„oommliammwomorsoragasakersaywoommw

CAROT

T4.T..62.62 Phonooardiographic recordings from the aortic area frequency) and mitral area (low f requency) to show the third and fourth heart sounds (S a d s ). External carotid pulse is also recorded. 3 n 4

E • T •

A.A. .N1- H.F•

L. S • E • 1 ,„ H • F•

Fig. 63 High frequency recordings from the aortic area and the left sternal edge to show diamond shaped systolic murmur in early systole — 215 —

A • W.

S M

DM

A • A • w0000,,v 1.1 • F •

M • A • H • F •

Fig. Of Systolic and diastolic murmurs after aortic valve replacement

K • H •

Fig. 65 The variation of the amplitude of the systolic murmur with the preceding cycle length "'<';';; .... 216- DPJ!Dl p!!ONQ9AR1?lorrIWm£ PmiIW XI.£Amm l\fDR. Amm;RWD· 11fHt!?J!1!ll Patient JIeaIl JlMn Cor:reo,Keaa. CorTeO...... lean I...... Q-% Q-I Q-II Q-II Ej. tble ... s~. E3.% r-ea I-e1 5Pc· $6:- $U' sec- sec· .see- ~~., B.A. 0.8ft.O 0.046 0.0.50 O"m.. OJt1, 0.248 29.5 0,098 0.141 l.A. 0.672 0.096 0.117 0.3'73 0.It-" 0,186 ·27.6 0.09ft, 0.187 S.A. 0.701 0.06 0,072 0.311 0•.'512· 0.177 25.3 0.100 0.143 I.A. o.G8It. 0,0'+8 O,OSS 0.)25 0.'92 0.179 26.2 0.102 0.149 G.B. 0.707 .- 0.360 0.428 0.267 37.8 0.095 S.D. 0.622 0.076 0.096- 0.'51 0.44' 0.195 '2,6 0.081- 0,156 J.B. 0.720 0.058 0.068 0.".7 OJ.09 0.212 19.0 0.079 0,13' l.C. o.sr.s 0.057 O.on 0.-'12 0.422 0.145 26.' 0.122 0.170 LB. 0.5ft,O ...... 0."., 0.475 0.169 31.' o.ns If.E, 0.900 ...... 0.172 19.1 O.U'- '.r,I', 0.673 O.~- O.U, 0.'91 OJ+8'e. 0.202 30.0 C.lca 0.201- E.G. 0.480 0.08, 0.119 0.290 "'O.u.$ 0.145 29.2 0,075 0.14ft. '1,G. 0,182 .0.066 0,075 0.)14 0.355 0.18' 0.070 0.132 E.U. 0.787 O.08S 0.0" 0,378 0.426 0.214 27.22''''' 0.073 0.167 E,H. 0.778 0.0'4 0,073 0.362 Ot410 0.219 28.1 0._ 0.141 J,H. O.SItS. 0.0" 0.012 0.297 OJt.01 O.ler.. 0.0$ 0,U7 »,B. 0.51.0 ...... 0."., 0.1+77 0,16, ".G31.0 0.U5 1',1. 0.623 O.OU 0.052 0.275 0."., 0.180 28.9 0.0'9- 0,097 P.E. 0.133 0.050 0.058 0.'50 0.409 0.2Oft. 27.8 0.101 0.148 Z.le. 0.761 o.Oft.7 .0.0"," 0.374- 0.1+.29 0.262 3If.Jt. 0.05' o.m !'.L. 0.628 0.079 0.100 0•.385 0.485 0.218 3It-.7 0.092 0.17' R•••. 0.et.4 0.068 0.074 0.''''''' 0.363 0.17S 20.7 0.100 0.160 . B••• 0.780 0.087 .0.099 0.174 o.ur. 0,224- 28.7 0.062 0.149 0.587 0.055 0.072 0,267 0.31.' 0.1&6 28.3 0.055 0.102 I."P.)I. 0.650 0.31+8 0.060 0.311 0.,J86 0.213 32.8 0.053 0.103 '0.867 o.or..' 0.<».6 0•.31.' 0•.371 0.197 22.7 o.ua 0.150 J.O.E". 0.68l· 0,059 0,072 0.-'09 0.37S 0.1"9 2OJt. 0.100 0.171t- P.P. 0.658 0.058 0.072 0.", a.us 0.186 28.3 0.091 0.148 . 1I.11, 0.628 O.OS' 0.071 0.352 0.444 ·0.187 44-.4 a.u, 0.16ft. E.R. 0.120 0,100 O.US 0.'62 0.426 O.let.. 26.0 0.016 0.174- I.S. 0.82ft.. 0.066 0.080 O•.5Oft. 0.335 0,179 21.7 0.066 0.123 E.S. ·0.'51 0.068 0.092 0.326 0.4.'9 0.177 "2,1 0.07S 0.151 G.S. 0.727 0.070 0.082 0.3BII. 0.450 O.21~ 29.6 o.n, O.lSO , P.S. 0.652 0.398 0.493 0,216 ·3'.1 0.208 E.'.r. 0.68L 0.0""- o.or..o- 0•.'562 0....'9· 0.2:.1 .~." o.OS,- 0.1.14- G.'.r. 0•.580 0.0ft.6 0.075 0.298 O.Jt8le, 0.210 55.3 0.052 0.096 P.If. 0.589 O.05ft, 0.07' 0.323 0.421 ·0.179 30."- .0.09' 0.142 W.W. 0.522 0."9 0.469 0.208 ".8 • 0.137 A.W. 0.911 0.056- 0.059- 0.'79 0.'97 0.282 31.0 O.or..o 0.095 D.W. 0.617 0.051 0.065 0.31t8 Oeltlt-, 0.210 "..0 0.095 0.146 A"eragea 0.678 0.062 0.017 0.34-2 0.420 0.198 .30.2 0.Oa5 0.11,., — 217

to be constant in all t t patientsstudied, and canseg the values for these intervals sere corrected in an appropriates manner.: The electricol..mechanical interval (Q4irst myna interval was prolonged beyond the normal range and the ejection time shortened Q.ealve closure click interval fo nd to average 04,342 seeond• This was within tau nail range (Shah, 194) because the changes a eotl.on time on one howl, and the changes in the electrical..meehanical interval on the other, were in op clime and nearly equal The relied was t roll When the mean values for nt ' Plotted t other« the other hand, When the relationship vas exam:dm individual, it wee clear that the trioal-meehezdoel interval and the isometric, *entree- tics interval were inversely related, and the ejection time directly related to the heart rate. This suggested that the duration of the phases of the eardiac wale varied widely in the individual patients, and closer examination showed that the duration of ejection time, ftr example, was longer in those,patients 'hose operation Imo Some time presioualg

VII " Pm9NocwiFoRAPpr rugNGwrrinuAss Tao types of arrhythmlas occurred in the patients ds (a) atriol fibrillation and (b) ventricular extrasysteles (a) Atrial TWi/lations The ejection time and the amplitude of eystolic murmurs varied followed the long eardiae oyole may have been due to ern Szs subsequent to the long diastolic filling

sis to al thus (Fig. 66)i and although thee f rtet hest sow record. ed (i.e. the atrio-ventrioular valves closed) no clicks far secoad heart sound were detectable. then the extrasysteles were not very earkY, the aortic valve opened and closed but the ejection phase was much shortened (Fig. 68). The degree of shortening depertded on the length of the previous diastolic interval In some instances, the orb:wore les were followed by a noreal t and seoond heart email but without the usual valve opening click (Pig, 67). Instead there was a pause fora period. of 0.22 second and then the usual second heart sound (i.e. artifielal valve closure sound) followed. In these patients the force of the eotopie beat was sufficient to displace the ball from the ring but not sufficient to push it, to the tip of the cage. Therefore, the valve opening click was not, produced. Whenever the extrsaystoles sere followed by a compensatory pause the post-extrasystalic beats were also altered (Pig. 69). Owing to the longer preceding diastolic interval, these beats had a longer ejection time and shorter Qovalve opening *lick interval then other - 219 -

E• R•

AORTA

011\10WilmeopoRARI\

66 Simultaneous phonocardiogram from the aortic area and- pressure tracings from the aorta and pulmonary artery (PA) to show multiple ventricular extrasystoles with non opened aortic valve -220-

K • H•

M.F.

M-A- H•F•

Fi5. 67 Phonocardiogram from the aortic area (medium frequency) and mitrel area (high frequency) to show the effect.of change in cycle length on the heart sounds and murmurs after aortic valve replacement H • A •

A•A• M.F.

M•F•

Fii . 68 Recordings from the aortic and mitre' areas (medium frequency) to show a short ejection after a ventricular extrasystole. - 221 -

G. 0 •

A •A • M•F•

M •A • M • F•

Ex

Fig. 69 The effect of extrasystoles and post extrasystolic beat on the heart sounds after aortic valve replacement.

1•F •

A•A• H.F.

WA- H.F.

Fig. 70 Hida frequency recording from both aortic and mitral areas to show the sounds produced after aortic and mitral replacement. wales.

There was no change in h valve l pening end *losing • clicks after the extraeystoles. FHONOCARDIORAPHY AFB ImApvuLER Five patients had both sortie and mitral valves replace. bye proathesis. In these, a Hammersmith valve was used for tral replace• meat and a ball.aml.cage valve was used for sortie replacement. Two patients had pre- and postoperative phanocardiograms. The phomooardiograms of the two patients shoved a tomb tion of the sounds produced by each of the prostheses (Fig.). short, high frequency Hammersmith valve closure sound sucoeeded the Q wave of the electrocardiogram by an average of Oa* mond and was followed by an interval of about 0468 second that represented theismeetric oontraotion period. This was terminated by the opening click of the belle valve. There were one or more aortic. valve clicks during systole and than the aortic valve closure Sound was inscribed. A period of 047 mooed ensued representing the isometric relaxation period and then the Hammersmith opening sound was recorded. All valve sounds were similar to those produced in the patients with single lave replacement. No phonooardiogramss were recorded after comb mitral tricuspid valve repleoement. 'COM After mitralvalve repldoement, phonooardiography was of some value in stwteing the performanoe of the mitral prosthesis. The

223 a.

and the artificial valve opening sound are rough criteria of the left atrial pressure (Wells, 3.954), These intervals could not be correlated with the previous cycle length in our patients It was iher ore concluded that the 1Wmmersmith prosthesis was not tomtits The phonocordiogram vas alav used to measure the mitral diastolic flow period. Both the cardiac output and.the diastolic filling periods were essential in order to calculate the mitral diastolic flow. a phono offered an excellent opportunity for the study of the dynamic) le ormexsoe Or the ball.and.eage mortis prosthesis.. By analysing the results of the cinematographio recording ofvelve movement in au artificial hydrualio *Atm using a pulse duplicator, and then .eorrelating the phonocardiograOhic sounds of the bell.and valve with the pressure pulse 'save in the ascending aorta, it was possible to understand the significance of each of these sounds and indicate their causes. Then the loft ventricular preesure exceeded the pressure in the aorta in early wet:oleo the silestic ball was dis- lodged from its ring. This movement produced every faint SOUnd that was not audible and hardly recordable. This sound van seen in the phonocardiograms with sufficient amplification as a series of small vibrations following the first heart sound► During the next few milli» seconds, the ball travelled the distance between the ring and the end of the cage. The contact between the ball and the tip of .tune cage was the cause of the first major *lick every sinus beat, The behaviour of the ball of with the varying physiological conditions. ejec stream very strong, lasting for a short period of time, ed in the distal part of the cage during the whole or the e phase and only one click reoorded in the phonooardiogran. ongerejection and weaker beats, the bell bounced and vibrated in t tenenal part of the cage and produced Witional clicks which were rata in the phcesoi. off. Weak beats (e.g extresystoles) sometimes dislodged the from the ring, thus producing the tiny initial sound but were la. capable of pushing the ball with enough force to the tip of the cage and therefore the larger valve opening click was absent.- Weaker beate did not open the valve altogether. The ventrioulerforee needed to open the valve depends theoretically on the specific gravity of the ball As the ball 13 nearly isobaric, with blood (its epsibific grail* is I very little force should be needed to effect an opening. This force was calculated experimentally by Harken et al for the ball valve (1962) They found theta, pressure gradient of 0.12 mm Hg is the mini mum needed to open the valve when the aortic diastolic pressure was 80 mm Ng. Tot, it seemed from the abundanoe at early beats with phose.. cardiogrOhic evideeoe of a non-opened valve that the valve actually needed a larger amount of force for its opening. Consideration of this fast led to the concluaion that multiple extrasystoles or, rapid at moy lead to abolition of the ejection phase in a significant amber of beats per minute and consequently to a marked reduction in the _ 225 .. cares* output. Establishing slow be paramount importance in the innedieft postoperati The ejection phase in these, patients significantly shorter then that of normal persona and was round to ac for 154 to 55.3% of the cardiac) oyole• The mean a jeold.csx per; .1% of the mean cycle length The ejection period measured can be used, together td-th the cardiac) outputs tiM10111, blood flow across the sortie prosthesis. " The shape and duration of the systolic murmur aortio atenosis are indicators of the degree of stenosis but ants 'ethic:1h mipport this conception cannot be applied to the tt uxmur heard after replaceront eith a. ball•endocage prosthesis, ¶ he produces considerable turbulence merely by. its presence in the aor and this may give rise to a munaur in the abeence of obstruction

en the other hands the intensity of the inurnrur MS found to be proportional to 'the preceding diastolie interval end. it may be that tivp occurrence of those murmurs in the early part of the ejection phase reflects the mull, gradient *doh must be established to overcome the inertia of the ball« The use of the phonocardiogram ► detecat ortd.a rocs teem had proved disappointing, The early diastolic murmur is difficult to record due to its very high pitch, lortio incompetenoe can, theoretically speaking/ be produced either through the ring of the valve or around it, subsequent to slipping of one of the stitches used in firing the valve. In all but one patient in this series, the — 22 inoocpetenco was found to occur arouna the valvering and in was repaired by stitching the ring to the aortic.annulue, In one patient, the uoompetenoe was due to fracture of the bell into several large pieces which lid not °ample seal off the oat Despite this, the opening olidkand second pound were quite non. RDA gave no clue to the dhanism of inoompetan di. 227 •

CHAPTER Ica

SUMMARY AND cCIICLUSICIM,

The natural hist ies of mitral incompetence aortic s and aortic incompetence are similar* Tho prognosis is usually good long as the patient is asymptomatic. Patients may remain in this beaten phase for a variable period of time, depending cm the severity of the valve disease and the state of the myncardium. The picture is completely changed for the verse once mymptoms start. After the advent of aymptoms, patients usually run a dovnhill course to final it oaPseitY and death in a relatively short period of time. In this final stage, medical treatment, though of help in ameliorating misery and improving morale, is of no definite value in prolonging life or preventing ultimate inoapaoity. At the present time, the only possible hope in this final stage is surgical relief of the valve pathology. Several surgical prooedures are available at the present time for

tackli these lesions, Plastic prooedures on the valves aimed at improving the functional perfeivianoe of the diseased valve, either by annuloplasty or by supplementing existing mop tissue, are of great value in only a limited number of carefully chosen oases. In most others, the valve pathology is usually found irretrievably advanced, and in them, total replacement is the only option available. Valve replacement by autogenous or homologous tissue holds the greatest promise as the moot logical and physiologioal approach. It offers the best

hydraulic performanoe and it avoids the prob3.ems of foreign body reaction, chemical inertness end mechanical strength of the synthetic valves. However, the technioal prohlems are at present prohibitive in the case of the mitral valve and still formidable, in the One, of the aortic valve. Until easy and simple techniques are available for sortie valve homo- or auto-graft implantation, and pending the aisevery of a satisfaotory mitral valve home.; or au graft, the impromummat and perfection of a synthetic prosthesis must continue In order to understand the dent gn of a prosthesis favor either aortic or mitral valves, a careful review of the hydraulic laws of fluid flow and of the anatomy of the cardiac ekeleton, ventricular cavity and flow pathways was made. The rules governing the choice of presthetio material for the valve were oleo described.► It was concluded that the best pros- thesisTor the mitral valve should have a round edged orifice. As the left ventricular cavity was shown'to be cylindrical in shape during gystole and the mitral valve leaflets form a part of its wall, it was concluded that the long axis of the valve mechanism =et be parallel with the long axis or the left ventricle, i.e. parallel with the plane of the prosthet- ic valve ring. The reverse sae found to holdtrue in the case of the aortic) valve prosthesis. All forms of mechanical hingee were found liable to failure and must not be used. The self-retaining mechanism was found to be ideal., because only this type of mechanism can °leave" the left ventricular cavity form part of the left ventridular wall during eyetole; it therefore offered no interference to the ejection of blood from the left ventricle to the aorta. The caged. valves were found to be undesirable in the, mitral area, because the lon axis of the cage was pempendicular to the exis of the left ventricular cavity and thus interfered with ventricular contraction, and because the cage remained in the left ventricular outflow tract during syatxsle and offered some interference to the blood flow into the aorta The superior mechanioal ana physical properties of polypropylene as well as its ohemical and biological inertness made it partioolarly suitable for the eneufaeture of valve prostheses, The consideration of all these factors culminated in thee, design of the Hammersmith prosthesis which Ras desoribed in detail and its various parameters were measured. The general rules for the experimental evaluation of prosthetic valves 'were summarised and applied to the Hammersmith prosthesis, Tests on valves with internal orifice diameters of 2,00, 2.25 and 2.5 am showed that only small pressure gradients were necessary for driving fluid across the valve in volumes corresponding to those required by the human body during rest and moderately severe exercise, No difference vas found between the performance of the 2.00 end the 2.25 cm. valves. In all three sires, any resistance to flow was found to be caused by the trap- door, and not by the ring. The optimal distance between the trap-doer and the valve ring to give the beet flow resistance was found to be 6 mm Turbulence appeared on the distal side of the valve with relatively small flow volumes; although it is believed that much less turbulence is likely to occur in the heart due to the higher viscosity of the blood and the lower velocity of flow. The dynamic characteristics of 230 -

the valve were found lobe euoellent, The results of eurgioal replacement of the mitral valve by the Hammermnith prosthesis were reviewed and the mortality figures wore carefully analysed, The high mortality was found to occur only in the immediate postoperative period and was attributed to metabolic and myocardial causes rather than mechanical failure of the proethesisi Review of the autopsy data seemed to confirm this view, since, in all but one patient, the prosthetic valve to be mechanically satisfactory. ftwombalmobale phenomena requent. Investigations were performed on twelve ratiento after mitral valve replacement by the Hammersmith prosthesis. The diastolic flow period was found to be relatively short due to a combination of rapid heart rate and long ascend hoart sound valve opening click interval. Owing to the brevity of the diastolic filling phaee, the actual flow rate across the prosthesis per unit time during diastole was found to be very high and, in some eases, more than three times the cardiac output. This discrepaney between the cardiac output and the mitral valve blood flow was found to be greater at more rapid heart rates. In five patients the gradients across the prostheses were found to be greater then those expected from the experimental studies on the pulse duplicator, The reason for this discrepancy was found to be mirily due to the ahortominge of the prooedure used in cardiac catheterisation. The valve was found to be competent in all but the °clippie cycles. Its dynamic characteristics were juiced to be excellent because the eloeure time was less than 10 milliseconds and the opening time was 5 10 milliseconds.

Phonocardiograms reoor pa r. f the

mitral valve with the Hams o rest. Their various intervals ware carefUlly meaeared end anal ed. The second heart soundsvalve Opening click and the'Qylalve closure click intervals could not be correlated with the length of the *wading oardiso (Wale.' It was therefosooncluded that the prosthetic valvea-were not stoma°. The double opening snap frequently noticed in the phonooardiograms was found to' correspond to the taro-stage opening process of the prosthetic valve which was noticed during cane study of the valve action in the pulse duplicator. The diastolic flow period was estimated as the interval between the valve opening click and.the.enbsequent valve closure °lick, and was used {to ther with the cardiac output) to'calculate the mitral blood flow during the open phase. The effects of mitral valve replacementthe a xcissicnm of the papillary muscles on the phyaiology of ventricular action was investigated. Movements of the atrio-ventricular ring were eaaminod before and after replacement and were fbund in be identical. 1-was concluded that excision of papillary muscle, usually performed prior to replacement, As of no effect on the novemonts of the mitral annulus aura.' that the action of the papillary muscles probably does not contribute a great deal to this movement. The peak dp/dt of the left ventricle was measured mathematically in subjects after mitral valve replacement and was found to be within the normal range. It was concluded that valve replacement and excision of papillary muscles probably has no adverse effect on left ventricular contraction. No detailed study of the hydrauli Starr.Edwaras aortic( prosthesis was attempted in view of its decreasing popularity in favour of home- and auto*grafts and because the valve has been extensively studied previously by other workers, However* the dynamic function of this valve ?Axe examined both everiraontally by seine studies in the pulse duplicator and. clinically by analysis of the phonooardiographic sounds produced by the prosthesis and by compering these sounds with the simultaneously recorded central aortic pressure tracings. The departure of *Iv ball from the ring was found produce a sound. of w amplitude, bail was seen to spin throughout the opening phase and to bounce of times after impinging on the tip of the cage These bounces were found to correspond to the multiple ejection clinks noticed in the phonocardiogram Extresystoles were found either to create enough force to dislodge bad. from the rings, but insufficient to push it nail1110 the tSp of the oage (thus no clicks were produced) or, if they were weaker still, the valve did not open at all and the ball remained stationary. A threshold foroe seemed to be needed to open the valve since in many cycles premature beats were unable to open the prosthesis. These conclusions were confirmed by examination or phonocardiogrems and aortic pressures recorded simultaneously. consideration or the above facts indicated that multiple extrasystoles or rapid atrial fibrillation may lead to abolition of the eject3...2a_ phase :.'ram a significant number of beats and consequently lead to a.'marked ,redt.totion of the ()waists output. Establishing a slow regular rivibm is believed. to be of paramount importance in the immediate postoperative period. 233 •

The ejection phase was ouna to be shor to vary directly vzith the length of the preceding cycle, The ation of aortic valve closure sound was not found o help in differeneating prosthetic from peri-prosthetio incompetence, CRS

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L. PREGER M.B. Manc., D.Obst.

M. K. A. DAYEM M.B. Cairo, M.R.C.P., M.R.C.P.E.

J. F. GOODWIN M.D. Lond., F.R.C.P.

R. E. STEINER M.D. N.U.I., F.R.C.P., F.F.R.

Reprinted from THE LANCET, October 9, 1965, pp. 701-706 ANGIOCARDIOGRAPHIC STUDIES OF Dotter and Steinberg (1951), Steinberg et al. 41958), PERICARDIAL DISEASE and Steinberg (1961) called attention to, the abnormally broadened soft-tissue shadow comprising pericardium, L. PREGER myocardium, and pericardial fluid which on angiocardio- M.B. Manc., D.Obst. graphy bordered the opacified right atrium. They did CLINICAL INSTRUCTOR (RADIOLOGY), UNIVERSITY OF CALIFORNIA HOSPITALS, SAN FRANCISCO not differentiate, however, between chronic constrictive pericarditis and pericarditis with effusion. Figley and DAYEM M. K. A. Bagshaw (1957), using angiocardiographic techniques after M.B. Cairo, M.R.C.P., M.R.C.P.E. a venous injection to study circulation-time, showed that RESEARCH ASSISTANT IN CLINICAL CARDIOLOGY the opacification-time was prolonged in chronic constric- J. F. GOODWIN tive pericarditis. They noted also that the lateral border M.D. Lond., F.R.C.P. of the right atrium was straightened in chronic constrictive PROFESSOR OF CLINICAL CARDIOLOGY pericarditis but not in pericarditis with effusion. They R. E. STEINER found that in 8 patients with chronic constrictive pericard- M.D. N.U.I., F.R.C.P., F.F.R. itis the thickness of the right atrial extraluminal shadow PROFESSOR OF DIAGNOSTIC RADIOLOGY ranged from 5 to 8 mm., whereas in 7 patients with From the Departments of Medicine (Clinical Cardiology) and pericardial effusion the range was 10-40 mm. Radiodiagnosis, Postgraduate Medical School, Hammersmith Hospital, London, W.12 Patients and Methods We describe here a series of 15 patients with chronic con- CHRONIC constrictive pericarditis and pericardial strictive pericarditis, 8 with pericardial effusion, and 9 without effusion are usually identified by the differences in the pericardial disease. Angiocardiography was carried out in the clinical and radiological findings; the hmmodynamics in patients with pericardial disease to aid in the differential the two disorders are similar. Definitive diagnosis is diagnosis between pericardial effusion and constrictive peri- important because the cause and treatment are different. carditis, and to exclude cardiomyopathy. Patients without Whereas chronic constrictive pericarditis is commonly pericardial disease underwent angiocardiography for various treated by resection of the constricting portions of the disorders which did not impair left ventricular filling (table I). Pericardial effusion was confirmed by the aspiration of peri- pericardium, pericardial effusion is managed medically cardial fluid. and by aspiration. Of 'the 7 patients with constrictive pericarditis whose Though typical cases of the two conditions are identi- angiocardiograms are available, the diagnosis was confirmed at fiable, there are many in which separation can be difficult, operation in 3. In another 3 the diagnosis was based on particularly in tuberculous pericarditis where it is occasion- clinical, electrocardiographic, radiographic, and hxmodynamic ally uncertain whether fibrous constriction has developed findings, but their clinical improvement on medical therapy or whether diastolic ventricular filling is impeded by has so far precluded the need for surgery. effusion or Gaseous granulation tissue. All 7 patients with chronic constrictive pericarditis had previously been on antituberculous therapy. 2 improved This report is mainly concerned with measurement of strikingly; 3 who showed no improvement after at least two the area and volume of the left atrium as an aid in the months' antituberculous treatment underwent partial peri- differential diagnosis between pericardial effusion and cardectomy; and 1 was transferred to another hospital, and constrictive pericarditis, and with the study of atrial records are not available. In none of the patients treated function in these two diseases. surgically were any tubercle bacilli detected in the resected portions of the pericardium. TABLE I—CHANGES IN VOLUME OF THE LEFT ATRIUM IN PATIENTS 1 patient with constrictive pericarditis and a 2nd with WITHOUT PERICARDIAL DISEASE

pericardial effusion had atrial fibrillation. All the others were

) in sinus rhythm. 1 patient with constrictive pericarditis l.

--... e lic §,-- underwent angiocardiography after the operation because his (m ng Patient Age Q,„, to %) Angiocardiographic improvement after operation was not considered satisfactory.

( Clinical diagnosis

no. me (yr.) ''''''' ias diagnosis 1 1 Cha Though there was still evidence of pericardial thickening, the lu D

vo -.' failure to improve was considered to be due to myocardial

' — insufficiency rather than to constrictive pericarditis, because 1 19 M 60 47 24 Pericardial effusion Normal 2 25 F 50 24 52 Pulmonary emboli Normal the size of the heart and atrial fibrillation increased pro- 3 16 M 42 34 24 Left to right shunt Normal gressively after an adequate pericardial resection. 4 34 M 48 27 43 Mediastinal mass Thymoma (surgical proof) An indubitable cause could not be given in any of the patients 5 29 F 67 25 62 Pulmonary embolus Pulmonary embolus with pericardial effusion; 1 patient had associated systemic 6 13 M 48 33 32 Pulmonary stenosis Normal 7 15 F 41 20 51 Pulmonary stenosis Normal lupus erythematosus ; I had long-standing rheumatoid arthritis; 8 16 M 49 27 45 Pulmonary stenosis Minimal pulmonary and 1 had scleroderma. In none were tubercle bacilli identified stenosis (catheter data) normal at in the pericardial aspirate. angiocardio- The cases were analysed on a basis of a study of the plain graphy 9 28 M. 86 43 50 chest-film, of fluoroscopic findings, and of the angiocardio- Hilar tumour Hilar tumour grams. Average change in volume, 43%. Plain chest X-rays were examined in the posteroanterior and 4 the lateral views for the following: cardio- thoracic ratio; size of the ; size of the aortic knuckle and pulmonary artery contour; shape of the heart; site and extent of calcification; size of the individual cardiac chambers; and shape of the cardio- phrenic angle. Fluoroscopy results were reviewed for those patients with chronic constrictive pericarditis and pericardial effusion who had been fluoro- scoped for cardiac chamber movement and presence of calcification. Angiocardiography was carried out through the right atrial route in 7 patients with con- strictive pericarditis, and in 8 patients with pericardial effusion. The right ventricular route was used in patients without pericardial disease. One ml. per kg. body-weight of 85% Hypaque ' was injected, and serial films were taken. All the angiocardiograms were pre- ceded by routine right-heart catheterisation. The pressure in the right atrium, right ventricle, pulmonary artery, and pulmonary capillary wedge were recorded and the pulse- wave form was analysed. Cardiac output was estimated by the Fick principle in every case. Simultaneous electrocardiograms were re- corded during angiocardiography. The maximum diameter of the right atrial cxtraluminal shadow was measured on the anteroposterior diastolic films of the angio- cardiogram above the level of the pericardial pad of fat. This is a measure of the thickness of right atrial myocardium, epicardium, peri- cardial effusion, and/or pericardial thickening. Fig. 2—Anteroposterior (above) and lateral films (below) of an anglocardiogram of a patient with pericardial effusion to show method of calcu- lating left atrial volume in systole (left) and diastole (right). Pleural effusion was never so large as to interfere with the measurement. The area and volume of the left atrium was measured during diastole and systole by the method described by Arvidsson and Odman (1957), Arvidsson (1958), and Steiner, Jacob- son, Dinsmore, and Parizel (1963). The area and volume changes from diastole to systole are proportional to the degree of diastolic ventricular relaxation. The left atrium was chosen because it is always well defined and conforms to a typical geometrical pattern. Similar attempts to measure the area of the right atrium and right ventricle were frustrated, since they were usually ill-defined and the overlap of the right atrial appendage by the opacified right ventricle varied. The results of the measure- ments for these chambers are therefore not included here. In all cases the left atrium filled with con- trast medium was traced on the X-ray film in both the anteroposterior and lateral pro- jections, and in each view when the chamber was expected to be at its smallest systolic and greatest diastolic size. This was estimated from the electrocardiogram taken at the time of angiocardiography. Left atrial minimal systolic size was coincident with the s wave. The peak of the T wave indicated the maximum left atrial diastolic size. Right atrial diastole occurred shortly after. Fig. 1—Anteroposterior (above) and lateral films (below) of an angiocardlogram in a patient without pericardial di . Area Measurement Left atrial area in systole (left) and diastole (right). The matrix grid ruled in 0.5 cm. squares was 5 placed over each tracing (fig. 1), and the size of. the left atrial chamber in diastole and systole was measured in sq. cm. in the manner described by Steiner et al. (1963). To permit a numerical comparison of left atrial area changes from diastole to systole in patients with chronic constrictive pericarditis and pericardial effusion the following formula was derived : Systolic reduction in size= Diastolic area systolic area in sq. cm. —in sq. cm. x 100 Diastolic area in sq. cm. The diastolic area was the mean area taken from the antero-posterior and lateral pro- jection during atrial diastole. Similarly the systolic area was the mean area taken from the antero-posterior and lateral projections at time of atrial systole. No measurements were made during extrasystole or post-extra- systolic beats. Volume Measurements Left atrial volumes were measured by means of tracings already described according to Arvidson's method (1957, 1958). One half of the transverse diameter of the left atrium in the frontal view and both long and short half- diameters in the lateral view were measured to the nearest mm., and volumes were calculated according to the formula: axbxc 4 1.28 x 1.26 x 1-26 x 3 n where a =half transverse diameter measured in the antero-posterior view; b = half vertical Fig. 4—Anteroposterior (above) and lateral films • (below) of an angiocardiogram in a patient with chronic constrictive pericarditis treated medi- cally. Note great diminution in lateral films of atrial size in systole (left).

diameter measured in the lateral view; and c = half anteroposterior diameter measured in the lateral view (figs. 2, 3, and 4). The left atrial appendage was excluded from both surface and volume measurements as suggested by Rudhe (1964). The magnification factors in the denominator of the equation (1.28, 1.26, and 1.26) were estimated geometrically by the measuring tube-to-film, and tube-to- patient distances on the angiocardiography table used in these investigations. Results PLAIN FILMS Chronic Constrictive Pericarditis (15 Patients) Calcification of the pericardium was present in 5 patients, gross in 4, but slight in 1; in 4 it was present mainly near the left ventricle; and in 1 calcification encased all four chambers. Pleural effusion was present in 6 patients, and in 2 was bilateral. Superior vena cava and azygos vein enlargement (used as an index of raised systemic venous pressure) was present in 5 patients. This was judged qualitatively. The cardiac silhouette in the posteroanterior projection showed no con- Fig. 3—Anteroposterior (above) and lateral (below) films of an angiocardiogram in a patient with chronic constrictive pericarditis treated surgically. stant pattern, but the left-heart border was Note similarity of systolic (left) and diastolic (right) size. Pericardial calcification straightened in 5 patients. The cardio- present. phrenic angle varied from 38° to 112°.

6

TABLEII—X-RAY FINDINGS was no correlation between the response to medical treatment and the severity of hmodynamic changes in Chronic constrictive Pericardial effusion X-ray findings pericarditis (15 cases) (8 cases) patients with pericardial constriction. Pericardial calcification .. 5 0 ANGIOCARDIOGRAPHY Pleural effusion .. 6 4 Prominent superior vena cava In 8 patients with pericardial effusion the width of the or azygos vein .. 5 2 Straightening of the left-heart right atrial extraluminal shadow ranged from 3 to 50 mm. border .. 5 0 with a mean of 29 mm. In 7 patients with constrictive Flask-shaped heart .. 0 5 Mean cardiothoracic ratio .. 0.51 0.58 pericarditis this measurement was between 4 and 14 mm. (mean 9 mm.). The results in 7 patients with chronic constrictive Although the main pulmonary-artery contour was only pericarditis diagnosed on clinical and hxmodynamic apparent in 9 patients on the posteroanterior projection, grounds are summarised in table v. Angiocardiography the aortic knuckle was clearly evident in all. The cardio- was not carried out on the other 8 patients with chronic thoracic ratio was 0.51. constrictive pericarditis. Table vs gives the corresponding Pericardial Effusion (8 patients) data in 8 patients with chronic pericardial effusion whose No pericardial calcification was noted in the patients with pericardial effusion. Pleural effusion was present in 3 4 5 4 patients, being bilateral in 2. In 2 patients the superior vena cava or azygos vein was enlarged. A typical flask- shaped cardiac silhouette was present in 5 patients. The cardiophrenic angle varied from 40° to 93°. The aortic knuckle was clearly identifiable in 7 patients, and the contour of the main pulmonary artery could be seen in 4. i.6 A7 A8 a9 AO The mean cardiothoracic ratio was 0.58 (table it). FLUOROSCOPY 10 patients with chronic constrictive pericarditis were screened for cardiac pulsations: 6 were found to have moderate to pronounced limitation of cardiac pulsations on the right side of the heart, but the movements were free ninn r, , IA on the left side. In 2 patients the cardiac pulsations were limited all over the heart, and, in another 2, pulsations were free on all cardiac chambers. In the 1 patient with pericardial effusion, cardiac movement was reported as normal, and there was no pericardial calcification. Irregu- lar pulsation was thus a useful sign of constriction. Fig. 5—Cardiac silhouettes in chronic constrictive pericarditis. HlEMODYNAMIC S angiocardiograms were available. Table I gives the data The hxmodynamic findings in chronic constrictive on 9 control patients. The results are summarised in the pericarditis and pericardial effusion are given in tables scattergram (fig. 7). m and iv. The results show clearly that all cases of chronic The average change in the left atrial volume during the constrictive pericarditis conformed to the typical pattern. cardiac cycle for those with pericardial effusion was 39%. Although the changes ranged from mild to severe, there Only 1 patient had low volume changes of 15%; he had, in addition, atrial fibrillation. The average left atrial TABLE III—H/EMODYNAMIC FINDINGS IN PATIENTS WITH CHRONIC volume changes in the 4 patients with constrictive peri- CONSTRICTIVE PERICARDITIS carditis that did not improve on medical treatment was Right atrial Right Pulmonary Mean Cardiac 8.9%, and in the 3 patients who were treated medically Patient mean ventricular artery wedge output the average volume variation was 38%. In the patients no. pressure pressure pressure pressure (litres • (mm. Hg) (mm. Hg) (mm. Hg) (mm. Hg) per min.) with no pericardial disease, there was 43% systolic Group A: reduction of left atrial size. 1 15 35/ 10 35/15 23 2.9 2 18 55/22 35/70 25 Discussion 3 8 27/11 32/12 11 3.5 PLAIN FILMS 4 2 22/5 17/9 4 5.5 Of the two commonly accepted differential signs of Group B: 5 10 39/9 36/9 8 6.2 chronic constrictive pericarditis and pericardial effusion— 6 19 37/22 35/13 20 3.9 7 12 35/12 21/12 .. .. pericardial calcification and flask shape of the heart— calcification was seen in 5 patients with chronic constric- tive pericarditis, and a flask-shaped silhouette was present TABLE IVHIEMODYNAMIC FINDINGS IN PATIENTS WITH PERICARDIAL effusion. The other factors EFFUSION in 5 patients with pericardial analysed were insufficient to differentiate between these Right atrial RightPulmonary Mean Cardiac two conditions. These findings indicate the difficulty of Patient mean ventricular artery wedge Output no. pressure pressure pressure pressure (litres diagnosing pericardial effusion or constrictive pericarditis (mm. Hg) (mm. Hg) (mm. Hg) (mm. Hg) per min.) from plain chest-films alone. 1 6 36/10 40/19 10 69- FLUOROSCOPY 2 5 28/8 23/10 11 5.3 3 7 509 4510 14 3.2 Our results of fluoroscopic examination confirm that 4 4 40/4 44/20 12 90 5 11 31/12 31/17 14 2.3 cardiac pulsations are diminished in constrictive peri- 6 9 68/8 75/25 14 28 7 11 35/14 35/14 14 carditis. They also show that the right border of the heart is the place to look for this sign. The pulsation in con- 7 TABLE V—LEFT ATRIAL VOLUME CHANGES IN PATIENTS WITH thus permanently impairing diastolic ventricular filling, CONSTRICTIVE PERICARDITIS which could be ameliorated by . Only 1 of Age Diastolic volume Systolic volume Change these surgically treated patients had calcification. These Patient no. (yr.) Sex (ml.) (ml.) small volume changes may be the cause of the low stroke Group A: volume and low cardiac output commonly seen in this 1 32 F 110 98 9.0 2 40 M 72 63 12.5 condition. 3 46 M 124 123 0.8 Group B comprised 3 patients, 2 of whom responded 4 25 M 63 56 11.0 Mean =8-9% clinically to medical treatment similar to that given to Group B: patients in group A. Their clinical and hwmodynamic 5 24 M 66 42 33.0 findings were identical with those of group A (table III). 6 30 M 90 39 56.0 7 41M 147 110 25.0 Their right atrial and right ventricular pulse-wave forms Mean =38% were typical of that of constrictive pericarditis. The 3rd patient with pronounced left atrial volume TABLE VI—LEFT ATRIAL VOLUME CHANGES IN PATIENTS WITH changes underwent angiography after the operation to PERICARDIAL EFFUSION investigate the lack of adequate improvement. Angi- ography showed Age Sex Diastolic volume Systolic volume Change Patient no. (yr.) (ml.) (ml.) (%) only slight peri- I Chronic constrictive PericardialControls 162 86 53 cardial thickening 1 52 pericarditis effusion 2 53 gl 123 105 15

i which was not 3 57 .T 97 57 41 Group f 4 31 or 52 31 41 considered enough _ A i B 5 63 69 29 44 to account for his 70 - 6 58 87 45 48 _ 7 55 89 58 29 signs and symp- • 8 48 m 97 61 37 Mean =39% toms. Myocardial 60 - - insufficiency was • • • • • _ thought to be the 50 - • strictive pericarditis is irregular over various parts of the cause, as explained _ • , cardiac silhouette, whereas in pericardial effusion, • • • earlier. In group sK 40 _ • _ pulsation, though diminished, is symmetrically reduced B the mean left - • _ around the cardiac silhouette. atrial change in ,14 • • "' 30 _ _ ANGIOCARDIOGRAPHY volume from dia- 4.3 _ _ stole to systole • • • Analysis of values obtained for left atrial volume and _ area changes showed that, in patients with pericardial was 38%. This is 20 - effusion, the changes in left atrial volume throughout the in the same range - • A.F. - - •• - cardiac cycle fell within the same range as those without as the change in 10 • the left atrial _ - okr volume in the 0 patients with Av. 8.9% Av. 39 % Av. 43% chronic peri- Fig. 7—Changes in volume of left atrium cardial effusion (%) in different types of pericardial table vi who had disease. Group A: constrictive pericarditis treated a mean of 39%, surgically. Group B: constrictive peri- and the patients carditis treated medically. R5 t6A A7 A8 without peri- cardial disease (table I) whose mean was 43%. 1 of these 3 patients had pericardial calcification. In the sole patient with chronic constrictive pericarditis and atrial fibrillation, theleft atrial volume change did not exceed 0.8% of the original Volume. This particularly low figure was due to a combination of the effects of atrial Fig. 6—Cardiac silhouettes in pericardial effusion. fibrillation and pericardial constriction and to the large initial left atrial volume secondary to long-standing left pericardial disease. The only patient with less than normal atrial hypertension and stasis. Although the presence of changes had atrial fibrillation. atrial fibrillation may be expected to reduce the cardiac The corresponding data for chronic constrictive peri- volume variations in both chronic constrictive pericarditis carditis allowed us to separate the patients into two and pericardial effusion, the change in left atrial volume groups: A and B (table v, figs. 3 and 4) according to the was much less (0.8%) in the patient with constrictive degree of atrial volume changes during the cardiac cycle. TABLE VII—LEFT ATRIAL VOLUME AND PRESSURE IN PERICARDIAL Group A consisted of the 4 patients who did not respond DISEASE AND IN MITRAL STENOSIS adequately to a course of medical treatment by anti- Mean left Maximum left Volume change tuberculous drugs. Of these, 3 eventually had partial Disease atrial pressure atrial diastolic in left atrium pericardectomy and improved subsequently, and 1 patient (mm. Hg) volume (ml.) (%) was lost to follow-up after transfer to another hospital. Mirral stenosis All 4 patients had reduced amplitude of volume and area (Arvidsson 1958) .. 25 145 35 Constrictive pericarditis: changes of the left atrium from diastole to systole with a Group A .. .. 17 82 10 Group B .. .. 14 101 38 mean change of only 8-9%. In these patients, fibrotic Pericardial effusion .. 13 93 42 changes in the pericardium were probably irreversible, 8 pericarditis and atrial fibrillation than in the patient with early cases of constrictive pericarditis as well as in most pericardial effusion and atrial fibrillation (15%). cases of pericardial effusion the duration of the pathological The data for changes in volumes and area are in agree- changes is too short to cause atrial-muscle atrophy and ment, in that the same patients fall into the same group A hence cannot be expected to interfere with left atrial or group B, regardless of selection by volume or area data. output. The area data are easier to collate, since no formula need Summary be used. The volume data give an absolute value in ml., The volume of the left atrium and its variation during and, though valuable for chambers with a geometric the cardiac cycle was investigated in 7 patients with pattern, such as the left atrium and left ventricle, they are chronic constrictive pericarditis, 8 patients with peri- not helpful in irregular chambers, such as the right atrium cardial effusion, and 9 patients with no abnormality in the and right ventricle, where the area method is of potential pericardium or the left side of the heart. value. In pericardial effusion the changes in left atrial volume The explanation for the different ways in which varia- during the cardiac cycle closely resembled those in the tions in volume of cardiac chambers behave in different control group. In the 4 patients with more severe con- pericardial syndromes can only be conjectural. The strictive pericarditis who did not improve with anti- conventional view that constrictive pericarditis is character- tuberculous treatment and eventually needed surgical ised by relatively unyielding pericardium which impedes treatment, preoperative atrial volume changes were diastolic ventricular relaxation and filling and atrial significantly smaller than in the control group and in the emptying can be invoked here. patients with pericardial effusion. On the other hand, in The alternative hypothesis of direct limitation of atrial 2 patients with constrictive pericarditis who improved on expansion and filling by a rigid pericardial constriction medical treatment and did not need operation, the left may be considered. This may be feasible if, for any given atrial volume changes during the cardiac cycle were left atrial pressure, the volume of the left atrium is less in similar to those in the control group and in the patients patients with chronic constrictive pericarditis than in those with pericardial effusion. without constriction. But Arvidsson (1958) has shown Measurement of the volume of the left atrium may be that in patients with mitral stenosis there is no correlation useful in assessing severity, prognosis, and the need for between left atrial volumes and pressures. Our data surgery in chronic constrictive pericarditis. (table vii) show that, although those patients in sinus The thoughtful guidance of Dr. Cohn Grant has been of invaluable rhythm with constrictive pericarditis and small left atrial assistance in the preparation of this communication. One of us (L. P.) volume changes (group A) had a mean higher left atrial held a fellowship in radiological research of the James Picker Founda- pressure and a smaller left atrial volume than those in tion; another (M. K. A. D.) held a scholarship from the Government of the United Arab Republic. group B, the difference in individual patients was small; there were some patients with only small atrial volume REFERENCES changes who had a relatively large left atrial volume and Arvidsson, H. (1958) Acta radio!, suppl. 158. — Odman, P. (1957) ibid. 38, 81. pressure. Thus, we have produced no certain evidence to Dotter, C. T., Steinberg, I. (1951) Angiocardiography. New York. suggest that a thickened pericardium directly limits atrial Figley, M. M., Bagshaw, M. A. (1957) Radiology, 89, 46. Rudhe, U. (1964) Personal communication. movement. Steinberg, I. (1961) Am. 7. Cordial. 7, 33. — Von Gal, H., Finby, N. (1958) Am. .7. Roentg. 79, 321. An additional mechanism may be atrophy of left atrial Steiner, R. E., Jacobson, G., Dinsmore, R., Parizel, G. (1963) Clip:. Radiol. musculature subsequent to long-standing constriction. In 17, 113.

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