Br Heart J: first published as 10.1136/hrt.34.8.761 on 1 August 1972. Downloaded from British HeartJournal, I972, 34, 76I-768. Coronary sinus and subvalvular left ventricular aneurysm
Apsley Pellatt From the Department of Anatomy, Faculty of Medicine, University of Rhodesia, Salisbury, Rhodesia
The anatomy of the coronary sinus is briefly reviewed. Atrial reflux and efficiency of the ostial valve are examined. A heart showing a posterobasal left ventricular aneurysm is described, and it is suggested that concomitant obstruction of the sinal ostium may have caused the aneurysm. A simple flow experiment, and examination of zOO routine postmortem hearts and 42 foetal hearts suggest that: (i) atrio-sinal reflux does not normally occur except in foetal life; (ii) the valve of the coronary sinus ostium is probably a vestigial structure with little efficiency; and (iii) some cases of submitral aneurysm may be due to obstruction of the coronary sinus.
The coronary sinus is the terminal channel of occurs to the extent of causing a 5-6 per cent the coronary venous system. It drains the admixture I-2 cm proximal to the ostium bulk of the blood from the vascular bed of the only when right ventricular pressure is arti- left coronary and a small part of that of the ficially raised by partial occlusion of the pul- right coronary artery (Gregg, I948). It is 2-3 monary artery. With normal haemodynamics cm long, o-5-i*o cm in diameter, lies on the no sinal reflux occurs.
back of the heart in the posterior atrioven- Also working with dogs, Stein et al. (I969), http://heart.bmj.com/ tricular groove, and opens into the right in experiments with an electromagnetic flow- atrium between the orifices of the inferior transducer attached to the tip of a cardiac vena cava and the tricuspid valve (Davies, catheter positioned in the coronary sinus I-4 x967). cm from the ostium, have shown that reversal The ostium of the coronary sinus is de- of blood flow, if indeed it occurs at all, con- scribed as being guarded by a semilunar endo- stitutes less than i per cent of forward flow. cardial valve (Thebesian valve) which covers Would these findings be valid for the human
the lower part of the orifice. It is said to pre- heart? Assuming however that appreciable on September 27, 2021 by guest. Protected copyright. vent regurgitation of blood into the sinus reflux does in fact tend to take place, how during atrial systole, and may be double or efficient an antireflux valve is a single semi- cribriform (Davies, I967). lunar cusp (covering about 50% of the ostium A priori certain questions arise. as usually depicted) likely to be ? The question Is there any tendency for significant atrio- is posed for postnatal conditions: during em- sinal reflux during atrial systole in the normal bryonic or foetal life circumstances may well heart? Contraction of the atrium causes only be different. minor reflux into the superior vena cava (a If the greater part of the coronary blood large channel with a valveless ostium) con- from the left heart is drained into the coronary tributing to the 'a' wave of the jugular veno- sinus, would obstruction of the sinus or its gram, and the right ventricle relaxing in ostium predispose to myocardial damage in diastole (during atrial systole) easily sucks in the region of impeded drainage? The theo- blood through the wide tricuspid orifice. It retical possibility exists that infarction secon- seems improbable that any important degree dary to venous occlusion might occur. Gregg of sinal reflux even tends to occur. (1948) in his review ofthe coronary circulation Koberstein, Pittman, and Klocke (I969), quotes evidence that in dogs acute experi- using a sophisticated blood H2 dilution tech- mental closure of the coronary sinus alone nique, have clearly shown in dogs that reflux causes no great reduction in coronary arterial of right atrial blood into the coronary sinus (and therefore coronary capillary) flow. In dogs where both coronary sinus and anterior cardiac Received 2 August 1971. veins (the latter draining most of the right Br Heart J: first published as 10.1136/hrt.34.8.761 on 1 August 1972. Downloaded from 762 Apsley Pellatt coronary blood directly into the right atrium) examined under a magnifier (2 x ) and appeared have been occluded in a two-stage operation, normal. In particular, no atheroma, thrombosis, the animals have survived for a period of or narrowing could be demonstrated in the circum- months, due to development of several large flex branch of the left coronary artery supplying extramyocardial venous anastomoses and the region of the aneurysm. numerous superficial cardiac veins of The epicardial surface of the whole left ven- con- tricle showed obvious 'venularity', i.e. a network siderable size which were not previously ofnumerous, dilated, and slightly tortuous venules evident. highly reminiscent of the skin of the lower limb Whether these findings in dogs are applic- in the presence of severe saphenous vein insuffici- able to the human heart is unknown at present. ency. In addition the posterior vein of the left Bearing in mind the high incidence of coron- ventricle was very dilated, and the middle cardiac ary arterial insufficiency in human hearts, a vein somewhat less so. There was no narrowing or degree of coronary venous occlusion might other abnormality of the channel of the coronary well be highly significant. sinus itself. Valid answers to all these questions con- The ostium of the coronary sinus, however, appeared grossly abnormal. It was almost com- cerning the coronary sinus in man will only pletely occluded by an endocardial septum in be made when experimental evidence con- which were two small perforations each I to 2 mm cerning sinal flow and pressure changes under in diameter (Fig. 4). The surface of this septum varying conditions is available. was smooth and neither it nor the margin of the ostium showed any sign of vegetations, petechiae, Case report thickening, or other pathological features. The These questions recently acquired added relevance edges of the perforations were well defined. when a heart with a left ventricular aneurysm was No other abnormalities could be seen in this sent to the Department of Anatomy by Dr. T. heart. Ashworth of the Department of Pathology. The It seemed obvious that normal coronary sinus heart was that of an adult male African, estimated flow could not possibly have taken place through age 6o years (PM 301/70, Harari Hospital). these two minute apertures. It was, therefore, Relevant clinical findings are as follows: the postulated that the aneurysm was secondary to deceased was admitted to hospital on 23 June chronic myocardial ischaemia caused by venous 1970, for decompression of thoracic spinal tuber- insufficiency in just that region ofthe left ventricle culosis. He died for no apparent reason on 3 most likely to suffer the effects of chronic obstruc- August 1970. tion of flow in the coronary sinus due to a con- No previous history is available. http://heart.bmj.com/ Apart from the heart condition, necropsy revealed genital ostial septum. active chronic pyelonephritis without hypertensive Other postulated contributory factors were: changes, and spinal tuberculosis. (I) the postmitral region is normally the thinnest The aneurysm was situated on the posterior part ofthe left ventricular wall; and (ii) at maximal wall of the ventricle behind the posterior cusp of systolic contraction this region of the ventricular the mitral valve (Fig. I). The aneurysmal wall was cavity behind the posterior mitral cusp (itself composed of hard fibrous tissue, only 2-3 mm bulged into the atrium during systole) must be a thick at its deepest part. A central zone of calcifi- 'pressure cul de sac' in which maximal left ven- cation which gave a metallic tinkle when tapped tricular pressure is developed. with an instrument was later confirmed radio- Search of the published material revealed re- on September 27, 2021 by guest. Protected copyright. graphically. The aneurysm measured 4 cm at its ports of 40 to 50 cases of subvalvular (submitral mouth, was 3 cm deep, and raised a smooth, fairly and/or subaortic) left ventricular aneurysm, al- well-defined bulge over the posterolateral aspect most all in Negro subjects. In all but a very few of the external surface of the ventricle (Fig. 2). of these no aetiology had been determined. With- Over and around this bulge was a well-marked out exception the often detailed necropsies make fibrous pericarditis (Fig. 2a). No other abnor- no mention of the coronary veins. In particular malities were noted, and in particular the coronary the state of the coronary sinus and its ostial valve arteries were normal. A retrograde coronary veno- are never once referred to in these reports (Brink gram shows the relation of the aneurysm to the and Barnard, 1954; Chesler et al., I965; Edington coronary sinus (Fig. 3). and Williams, I968; Higginson and Keely, i95i; A diagnosis of submitral left ventricular aneu- Lurie, I960; Pocock et al., I965; Robertson and rysm of unknown aetiology was made. In view Jackson, I960). of reports of similar lesions from other parts of Therefore, it was felt that the findings in this Africa, and especially in view of tentative sug- heart merited further study, as there seemed to gestions by other workers that the aetiology may be a reasonable 'prima facie' case that the aetio- be a developmental anomaly of the 'fibrous valve logical connexion postulated above might be cor- ring' (Edington and Gilles, I969; Abrahams et al., rect. Three lines of inquiry were accordingly 1962), this heart was referred to the Department pursued. of Anatomy for further investigation. Preliminary examination confirmed the necrop- Methods sy findings. The fibrous valve ring was intact and In an attempt to establish that sinal flow must apparently normal. The coronary arteries were have been reduced, a simple flow experiment was Br Heart J: first published as 10.1136/hrt.34.8.761 on 1 August 1972. Downloaded from Coronary sinus and subvalvular left ventricular aneurysm 763 http://heart.bmj.com/
FIG. I Interior of left chambers of heart (PM 301/70, Harari Hospital), showing mouth of large submitral aneurysm. LA, left atrium; PC, posterior cusp of mitral valve. FIG. 2a Posterior surface of left ventricle showing well-marked fibrous pericarditis. FIG. 2b X-ray of heart (PM 301/70). Vertical wires mark position of cut edges of opened left ventricle. Circular wire marks limit of the aneurysmal bulge on external surface of ventricle. Note two partly separated loculi of the aneurysm (A and B), and calcification especially in the on September 27, 2021 by guest. Protected copyright. smaller loculus. Posterior view. FIG. 3 X-ray of same heart showing position of aneurysmal loculi relative to coronary sinus (CS). PV, posterior vein of left ventricle. A and B as in Fig. 2. Posterior view. FIG. 4 Ostium of coronary sinus (margin dotted) of heart (PM 301/70) showing its occlusion by an endocardial septum perforated by two minute apertures. TCV, tricuspid valve; RV, right ventricle; RA; right atrium; IVCV, valve of inferior vena cava. (These abbreviations also apply to Fig. 5-II).
,performed to compare flow rate in this heart with measured three times. The results are as follows, that in a normal heart having a patent sinal ostium each figure being the mean of three closely similar IO mm in diameter. readings. A reservoir of water was mounted on a stand above the heart. From this a tube was led and tied Normal heart: minute flow through tube alone, into an opening made into the coronary sinus 2-5 450 ml; minute flow through tube and coronary cm from the ostium. The apparatus was connected sinus, 450 ml. with a mercury manometer and the height of the reservoir adjusted to give a pressure of 8o mmHg. Pathological heart: minute flow through tube and Flow through the ostium into the right atrium was obstructed coronary sinus, 375 ml. observed and collected over a period of I minute. The procedure was repeated three times with This reduction in flow of 17 per cent was smal- each heart, and flow through tube alone was also ler than expected, but the experimental conditions Br Heart J: first published as 10.1136/hrt.34.8.761 on 1 August 1972. Downloaded from 764 Apsley Pellatt
TABLE I Variations in structure of the valve maximum degree of valve coverage, in the closed of the coronary sinus in 0OO unselected African position, seen was ioo per cent, which occurred in cadavers only one case. No specimen showed a condition remotely approaching the almost complete occlu- Male Female sion seen in the abnormal heart. Table 2 shows the range of measurements of No valve 2 the diameter of the ostium in the 52 adult subjects Single string: in the series. Thin
opened and a detailed inspection made. Particular These findings indicate the following. on September 27, 2021 by guest. Protected copyright. attention was paid to the coronary arteries and to the anatomy of the coronary sinus ostium. The i) In 5 cases (12%) the valve completely covers findings are presented in Table I. the ostium (ioo% coverage) when in the closed Fig. 5-II show the variations listed in Table I. position. This contrasts with the postnatal series The preponderance ofmales (63%) is explained (Table i) where maximal coverage was of the partly by the normally higher proportion of male order of 70-75 per cent in 3 cases and ioo per cent in-patients at Harari Hospital, and partly by the in only one. still higher proportion of males in the total num- ii) In no case was the valve completely absent: ber of medicolegal necropsies (6o% and 76%, this contrasts with total absence in two females in respectively). Table i. It should be noted that the textbook description iii) In only one case was an 'abnormal' valve seen, of the 'normal ' valve is what in Table i is termed showing a single large fenestration in an otherwise a 'full valve', i.e. a single semilunar cusp based normal cusp. Even here ostial coverage was 30 on the posteroinferior margin of the ostium, with- per cent. No case of multiple fenestration or re- out superfluous strings, and covering approxim- duction to single or multiple strings was seen. ately half of the aperture. Table i shows that 7 iv) No case of almost total occlusion comparable (ii %) male subjects and I0 (27%) female subjects with that in the aneurysmal heart was seen. have abnormal valves. In no case is there any narrowing of the ostium, whatever the state of The tentative conclusion may be drawn that development of the valve. Even in those subjects during foetal life the valve of the coronary sinus with cusps covering more than three-quarters of tends to be better developed than in postnatal life. the ostium in the closed position, there is ample During foetal life reflux into the coronary sinus room for sinal blood flow into the atrium. The may be potentially greater due to the copious Br Heart J: first published as 10.1136/hrt.34.8.761 on 1 August 1972. Downloaded from
Coronary sinus and subvalvular left ventricular aneurysm 765 http://heart.bmj.com/
FIG. 5 Ostium of coronary sinus. Specimen showing complete absence of valve (see Table I). FIG. 6 Ostium of coronary sinus spanned by single thin endocardial string. FIG. 7 Ostium spanned by a single thick endocardial string. FIG. 8 Ostium spanned by multiple strings. FIG. 9 Ostium covered by valve with numerous fenestrations. FIG. IO Ostium covered by 'full valve' giving 50 per cent cover. FIG. I I Ostium covered by 'full valve' giving 10O per cent cover. This was the only example in IOO postnatal cases. The next highest degree of on September 27, 2021 by guest. Protected copyright. cover (75%) was only seen in 3 cases. (Ostial margin dotted.) stream of blood (mainly of placental origin) which closed position in foetal life to complete ab- passes across the right atrium from inferior vena sence in postnatal life. cava to foramen ovale immediately above the Complete absence of the valve, obvious ostium of the coronary sinus. Sudden increase of fenestration to form a or flow due to maternal muscular activity would tend flimsy net, its reduc- to raise foetal right atrial pressure, further aggra- tion to one or more endocardial strings in vating the tendency to sinal reflux. In these cir- not a few cases - conditions which preclude cumstances a more efficient valve would be any valvular action, without apparent func- advantageous. tional disturbance - force the conclusion that in postnatal life this valve is a vestigial struc- ture of minimal importance. Discussion Its more complete development during (i) Examination of the morphology of the foetal life may be of functional significance in ostium of the coronary sinus in ioo postnatal preventing excessive sinal reflux during cadavers and in 42 foetuses in the midgesta- periods of augmented placental return. tional trimester makes it clear that there is The suggestion is made that after the nor- great variation in development of the sinal mal postnatal circulatory changes have taken valve, ranging from full ostial coverage in the place, further growth of the valve in all cases Br Heart J: first published as 10.1136/hrt.34.8.761 on 1 August 1972. Downloaded from 766 Apsley Pellatt
TABLE 2 Diameter of ostium of coronary the left coronary bed of the aneurysmal heart sinus in 52 adult subjects must have been shunted through anastomotic channels to the anterior cardiac veins draining Diameter of ostium Male Female into the right atrium. The area of greatest 5 mm or less venous stagnation under these conditions 6-io mm 23 9 would have been in the channel of the coron- II-I5 mm I5 3 ary sinus approximately 2-3 cm from the I6 mm or more 2 ostium - a region precisely adjacent to the area. area is normally the Total adults: 52 40 12 aneurysmal This thinnest part of the left ventricle, and also sustains the high pressure of blood 'trapped' in the 'pressure cul-dezsac' behind the pos- terior mitral cusp during ventricular systole. lags behind enlargement of the ostium, with the result that valvular closure is almost (iii) No case in either the postnatal or the always much less than ioo per cent, whereas showed any occlusion of the in foetal life total closure is more common. foetal series Furthermore, it is suggested that in keeping ostium of the coronary sinus comparable with with the altered right atrial haemodynamics that in the aneurysmal heart. This seems to be of postnatal life, the ostial valve is less subjec- supportive evidence that the aneurysm may developed secondarily to ostial ted to functional stress and as a result often indeed have occlusion. undergoes a process of degeneration and re- Since these investigations were completed duction, in a few cases to the point of disappearance. however, two other hearts from the Harari Hospital mortuary showing left ventricular (ii) Simple experiment showed that flow submitral aneurysms have become available for examination. In one the cause was obvious through a normally patent ostium of average diameter (io mm) is likely to be significantly - a total atherosclerotic occlusion of the cir- greater (I7%) than flow through an ostium cumflex branch of the left coronary artery to the aneurysm (Fig. occluded by a septum having only two small immediately adjacent 12 and I3). In both of these hearts the coron- apertures of i to 2 mm each, such as was present in the aneurysmal heart. Calculation ary sinus and its ostium were normal. These http://heart.bmj.com/ of the cross-sectional area ofthe smallest adult findings make it clear that the aetiology of ostium seen (diameter 6 mm) shows it to be submitral left ventricular aneurysms may five times greater than the combined area of involve several factors. the two apertures in the occluding septum. The ratio of blood flow is likely to be of a (iv) Bland, White, and Garland (I933) re- similar order of magnitude. ported the occurrence, in an infant dying at This seems to indicate that flow through the age of 3 months, of an abnormal origin of
these apertures must have been grossly in- the left coronary artery from the pulmonary on September 27, 2021 by guest. Protected copyright. adequate, and that much of the blood from artery, associated with marked dilatation of
TABLE 3 Variation in structure of valve of coronary sinus in 42 foetuses in mid-trimester of gestation Male Female Foetal age i3-i5 I6-i8 19-21 22-24 25-26 I?-I5 I6-I8 19-21 22-24 25-26 wk wk wk wk wk wk wk wk wk wk Ostial coverage by valve in closed position 5-25% I 2 - I - - I 30-45% 2 - 2 - I 5o-6o% 4 4 4 3 I 2 4 I - 65-75% - - - I - I 2 - - I00% - - 2 - - I I I S 6 8 6 I I 3 8 3 I Total foetuses 42 26 i6 Br Heart J: first published as 10.1136/hrt.34.8.761 on 1 August 1972. Downloaded from
Coronary sinus and subvalvular left ventricular aneurysm 767 the left ventricle, severe fibrosis of the endo- cardium, and occasional fibrotic patches at deeper levels. Concomitant apparent hyper- trophy of the ventricular wall 'was due in part to an increase in the number of muscle fibres, and in part to separation of muscle bundles by unusually large spaces, the result of vascular dilatation together with a small amount of fibrosis between the bundles'. The size of individual muscle fibres was not appreciably greater than normal. 12 3 4 5 6 7 S 8 n,e 12l; Their illustration of the interior of the left ventricle in their case shows a notably similar appearance to that of the aneurysmal region in the present case - obvious fibrotic trabecu- f 3 4 7 R 9 1) lae thrown into high relief by the rounded c;m 'blown-out' spaces between them. The authors make the significant comment FIG. I2 Interior of left ventricle (PM that the, 'parenchymal changes are dependent 8II/70, Harari Hospital) showing mouth of in large part upon two factors: (i) the in- submitral aneurysm (A). adequate nourishment of the ventricular wall FIG. I3 Posterior surface of left ventricle by venous blood and (2) the relatively low (PM 8/II70) showing haemorrhagic aneurys- pressure in the coronary artery arising from mal bulge on external surface. Position of the pulmonary artery'. They further note, atherosclerotic section of circumflex branch of 'the striking similarity of the ... degenerative left coronary artery dotted. Veins outlined by changes . . . to those arising ... secondary to radio-opaque material. coronary artery sclerosis'. Venous blood moving sluggishly at low pressure by hypopulsatile flow would likewise
result from occlusion of the coronary sinus, http://heart.bmj.com/ with presumably similar consequences for Hudson states that atresia of the ostium myocardial fibres in the vulnerable subvalvu- 'may occur in isolation or with other lar region ofthe left ventricle. Due to multiple anomalies; 3 types were seen': he then coronary venous anastomoses, these sequelae describes the three types occurring with other would of course take far longer than three anomalies. No further mention is made of months to develop. Most of the reported cases isolated atretic ostia; the number of examples of subvalvular aneurysms have only become described is not stated, and the condition is not illustrated. clinically apparent in the second or third on September 27, 2021 by guest. Protected copyright. decades of life. Yet it is precisely this isolated ostial atresia, with no easy alternative drainage channels, which could conceivably result in chronic, (v) Hudson (1970) has reviewed the anomalies localized, left ventriculat myocardial venous of the coronary sinus. Four main groups are congestion and consequent mural weakening. distinguished. (a) Enlargement. (b) Absence. Hudson also reviews the published reports (c) Hypoplasia. (d) Atresia of the ostium. on cardiac aneurysm in the African and quotes Both text and illustrations show that in that of Chesler et al. (I965), 'The aneurysms virtually every case these anomalies are seemed to be due to a congenital weakness of accompanied by other gross, often multiple, the left ventricular wall near the atrioventricu- cardiac abnormalities. Furthermore, blood lar junction, permitting endocardial hernia- prevented from flowing through a narrowed tion.' As already noted earlier in this paper, or absent coronary sinus is drained by one of Edington and Gilles (I969) and Abrahams et the following channels. (i) A persistent left al. (I962) have also expressed this opinion. superior vena cava. (ii) A pulmonary vein, Some of these aneurysms may well be con- usually the left inferior. (iii) Enlarged The- genital, in the sense that the herniation may besian veins draining directly into the atria. have begun in early life, or in that the pre- Left ventricular aneurysm is conspicuously disposing cause may have been insidiously absent in these cases of obstructed coronary operative from an early stage. What is this sinus flow. This is only to be expected, since, predisposing cause? May it not be, in some in effect, flow is not obstructed but merely cases at least, inadequate perfusion of the diverted into the foregoing channels. affected region of myocardium ? After all, the Br Heart J: first published as 10.1136/hrt.34.8.761 on 1 August 1972. Downloaded from 768 Apsley Pellatt one soundly established causal mechanism for G. Herrington ofthe Department ofPathology for certain examples of left ventricular aneurysm the excellent photographs; Miss G. Warren for arterial occlusion in assistance in examination of specimens; and the is coronary resulting poor Secretary for Health for access to material at the myocardial perfusion. Localized venous in- Harari Hospital Mortuary. sufficiency would likewise result in reduced tissue perfusion, albeit at a slower tempo. Isolated atresia of the ostium of the coron- References Abrabams, D. G., Barton, C. J., Cockshott, W. P., ary sinus without alternative large drainage Edington, G. M., and Weaver, E. J. M. (I962). channels (dilated Thebesian veins, persistent Annular subvalvular left ventricular aneurysms. left superior vena cava, or other extramyo- Quarterly Journal of Medicine (n.s.), 31, 345. cardial anastomoses) should be considered as Bland, E. F., White, P. D., and Garland, J. (I933). of localized venous insuffici- Congenital anomalies of the coronary arteries: a possible cause report of an unusual case associated with cardiac ency. In all future cases of otherwise un- hypertrophy. American Heart J'ournal, 8, 787. explained left ventricular aneurysm the Brink, A. J., and Barnard, P. J. (I954). Syphilitic coronary venous system should be critically aneurysm of the left ventricle of the heart with examined, and in all cases of isolated atresia calcification and ossification. South African Medical, Journal, 28, 476. of the sinal ostium the left ventricular myo- Chesler, E., Joffe, N., Schamroth, L., and Meyers, A. cardium in the region of the atrioventricular (I965). Annular subvalvular left ventricular junction should be investigated for signs of aneurysms in the South African Bantu. Circulation, venous congestion and tissue degeneration. 32, 43. Davies, D. V. (I967). Gray's Anatomy, 34th ed. Longmans, Green, London. (vi) The questions posed early in the paper Edington, G. M., and Gilles, H. M. (I969). Pathology may now be accorded tentative answers. in the Tropics, p. 317. Edward Arnold, London. Edington, G. M., and Williams, A. 0. (I968). Left atrial aneurysms associated with annular subvalvu- (a) Significant atrio-sinal reflux probably does lar left ventricular aneurysms. J'ournal of Pathology not tend to occur in postnatal life, but may and Bacteriology, 96, 273. well be of importance in foetal life. Gregg, D. E. (I948). The coronary circulation. Physio- (b) Efficiency of the ostial valve of the coron- logical Reviews, 26, 28. Higginson, J., and Keely, K. J. (I95i). An unusual ary sinus probably parallels the tendency to cardiac aneurysm in a young adult. Journal of atrio-sinal reflux. Manifestly a valvular cusp Clinical Pathology, 4, 342. covering only half or even less of the ostium Hudson, R. E. B. (1970). Cardiovascular Pathology, http://heart.bmj.com/ is not very efficient. Absence or reduction of Vol. III, pp. S.4oo and S.998. Edward Arnold, London. the cusp to a net or even a single endocardial Koberstein, R. C., Pittman, D. E., and Klocke, F. J. string indicates that little efficiency is re- (I969). Right atrial admixture in coronary venous quired, at any rate during postnatal life. blood. American Journal of Physiology, 2I6, 53I. (c) In at least some cases of submitral Lurie, A. 0. (I960). Left ventricular aneurysm in the African. British HeartJournal, 22, I8i. aneurysm, impeded drainage through the Pocock, W. A., Cockshott, W. P., Ball, P. J. A., and coronary sinus may result in venous conges- Steiner, R. E. (I965). Left ventricular aneurysms
tion and myocardial damage. Congenital of uncertain aetiology. British Heart Journal, 27, on September 27, 2021 by guest. Protected copyright. maldevelopment of the valve of the ostium I84. of the Robertson, J. H., and Jackson, J. G. (I960). Cardiac coronary sinus resulting in the forma- aneurysms in Nigeria. Journal of Pathology and tion of an occluding septum appears to be one Bacteriology, 80, IOx. possible cause of such impeded drainage. Stein, P. D., Badeer, H. S., Schvette, W. H., and Glaser, J. F. (1969). Pulsatile aspects of coronary Sincere thanks are due to the following persons sinus blood flow in closed-chest dogs. American who have contributed to this study: Dr. T. Ash- HeartyJournal, 78, 331. worth and Dr. N. Gane of the Department of Pathology, and Dr. M. Ross and Dr. K. Lee of Requests for reprints to Dr. Apsley Pellatt, De- the Government Pathology Laboratory at Harari partment of Anatomy, Faculty of Medicine, Hospital, all of whom collected postmortem University of Rhodesia, Private Bag M.P. I67, material for examination. Mr. N. Lyons and Mrs. Mount Pleasant, Salisbury, Rhodesia.