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Home , Auscultation, Cardiac surgery, Heart sounds, Pulse

: first published as 10.1136/thx.36.2.95 on 1 February 1981. Downloaded from

Thorax, 1981, 36, 95-98

Auscultation of the since Laennec

AUBREY LEATHAM From St George's Hospital, London

With the advent of accurate phonocardiography when using a rigid diaphragm , but in the early 1950s and with in the identity of the two components has been the the last decade to give the precise timing of valve subject of debate for the last 20 years.2-8 Initially, movement, of the heart is now on a it was assumed that splitting indicated asynchrony firmly established basis. of atrioventricular valve closure at the onset of In the pre-stethoscope era, perhaps the most ventricular , with the mitral component perceptive comment was that of Robert Hooke to before the tricuspid as suggested by the site of the Royal Society quoted by McKusick,l "I have maximum intensity and the relation to the carotid been able to hear very plainly the beating of a .2 Further support for this was the finding of man's heart.... Who knows I say that it may be increased delay of the second component in most possible to discover the motions of the internal patients with right bundle branch block with organs.. . ." ectopic beats arising from the left , and Laennec's great contribution to was with pacing from the left ventricle.3 With intra- the invention of the stethoscope in 1819. His main cardiac phonocardiography and experi- interest, however, was auscultation of the ments, however, the sound attributed to tricuspid copyright. rather than the heart. While he correctly timed valve closure could not be identified, and there the first heart sound to coincide with contraction was a strong school of thought in the United of the ventricle, unfortunately he attributed the States which denied the existence of vibrations second sound to atrial contraction and was thus originating in the right side of the heart.4 The

unable to make accurate correlations between situation has at least been clarified using high http://thorax.bmj.com/ murmurs and pathological findings. After Hope's speed, high definition echocardiograms simul- animal experiments which gave the timing of the taneously with phonocardiograms. It has now been first and second sounds (1832), rapid advances shown that the first high frequency component were made. By the end of the century nearly of the first sound is exactly synchronous with the every notion in use today had been described, in- final halt of the closing , and the cluding inspiratory splitting of the second sound second component, when separately identifiable, by Potain in 1866, but the accurate theories were is exactly synchronous with that of the tricuspid outnumbered by the innacurate, and proof of the valve.A57 The interval between the components origin of sounds and their significance could not (typically 30 ms) is greater than expected from on September 28, 2021 by guest. Protected be obtained until relatively recent times. the slight asynchrony of ventricular contraction and we have had to wait until very recently for a reasonable explanation of this phenomenon. It has now been shown that the precise timing of Heart sounds are divisible into relatively loud mitral valve closure is closely dependent on the high-frequency sounds, thought by Dock nearly P-R interval.8 Echocardiography has confirmed 50 years ago to be caused by the terminal halt of that atrial contraction and relaxation opens and opening and closing valves, and the low frequency, then closes the atrioventricular valves. With a soft (to the ear) ventricular filling sounds (third P-R interval of 0-16 s or more, left atrial con- and atrial) which will not be discussed further traction opening the mitral valve in pre-systole, here since no new light has been thrown on their also has time to close it almost completely. Thus mechanism. the final half of closure occurs very soon after Splitting of the first heart sound into two high- the onset of the left ventricular pressure pulse. frequency components can be heard over the Right atrial contraction has much less effect on lower end of the sternum in most normal subjects the timing of tricuspid closure, presumably be- Address for reprint requests: Dr Aubrey Leatham, St Georges' cause right atrial contraction is less effective, and Hospital, Blackshaw Road, London SW17 OQT. ejection is into a more flaccid ventricle. Thus 95

B Thorax: first published as 10.1136/thx.36.2.95 on 1 February 1981. Downloaded from

96 Aubrey Leatham the is more fully open than the sound. Distal block is usually associated with mitral at the onset of ventricular systole and more serious disease of the conducting tissue or of therefore takes longer to be closed. The difference the myocardium. It can be suspected when split- in timing between mitral and tricuspid closure, ting of the first sound cannot be detected, despite and thus the corresponding sounds, therefore electrocardiographic evidence of right bundle tends to be greater than the degree of asynchrony branch block. With pulmonary the of the corresponding ventricular pressure . isovolumic time of the right ventricle is usually Thus physiological splitting of the first sound may prolonged and the late opening of the pulmonary be surprisingly wide and the tricuspid closure valve can be detected by echo if a late ejection sound is sometimes difficult to differentiate from sound is not audible.15 This is a useful addition to an ejection sound. the other clinical and non-invasive signs of pul- Echo observations on the timing of mitral valve monary hypertension, namely a big A wave in the closure have also thrown light on the variation in venous pulse, a sustained para-sternal heave, an intensity of the first heart sound, which has been abnormally loud pulmonary component of the known for many years to be influenced by the second sound in relation to the preceding aortic P-R interval.9-"1 While echocardiography con- component, transmission of the pulmonary com- firmed the relation between intensity of the first ponent to the apex, and the usual electrocardio- sound and the position of the mitral cusps at the graphic and radiological evidence. Thus, moment of ventricular contraction, it seemed should seldom be a strange that varying distance of travel of such "catheter diagnosis" only. flimsy structures should cause such great altera- Aortic ejection sounds are caused by abnormal tions in intensity of sound produced by their final aortic cusps which remain mobile but cannot fold closing halt and it was suggested that late closure neatly against the aortic wall during ejection; they as in mitral was responsible for the loud can be identified precisely by echocardiography sounds.'2 It has now been shown that the wide open since they coincide with the final halt of thecopyright. valve associated with a short P-R interval, having opening valve cusps. Thus a haemodynamically a greater distance to travel, does indeed close normal bicuspid -the most common late.'3 Mitral closure is completed at a time when congenital anomaly of the heart-can be identi- the rate of increase of ventricular pressure is much fied. This is of interest since long-term follow-up of bacterial and greater, and so the valve closes with high velocity discloses a small risk http://thorax.bmj.com/ and creates a loud sound. When the P-R interval the variable development of calcific is long, however, atrial contraction has had time in later life.'6 17 An aortic ejection sound is almost almost to appose the mitral leaflets, and final invariably obvious with aortic valve stenosis unless closure will occur earlier when the rate of pressure there is gross calcification and is invariably absent change is minimal, producing only a soft sound. with subaortic obstruction unless there is an ad- an aortic way, echocardiography has been invalu- ditional bicuspid valve. Identification of In this the able for gaining an understanding of the principles ejection sound is also useful in deciding governing intensity and splitting of the first heart aetiology of aortic regurgitation, since it is almost sound in normal subjects. always present with a bicuspid regurgitant valve, on September 28, 2021 by guest. Protected observations, studies is occasionally present with a rheumatic regurgi- Following on from these is have been made of the time interval between tant valve, but is absent when root dilatation closure and the cause of the aortic regurgitation.'8 mitral and tricuspid have opening in right bundle branch block and in pul- The components of the second heart sound dis- been easier to identify and to understand, and monary hypertension. It seems possible to knowl- tinguish proximal right bundle branch block where echocardiography has added little to our the onset of ventricular contraction and tricuspid edge except for its ability to identify pulmonary cases when this is difficult on closure are late, from distal or arborisation block closure in some the onset of ventricular contraction is not auscultation, or occasionally even on a phono- where of an delayed but activation of the right ventricle is cardiogram. The major value understanding in both varieties the pulmonary valve of the second heart sound and its respiratory slow'4; the examination of children, in opens late. Proximal block is the usual explana- variations is in bundle branch block with whom "innocent" or physiological ejection systolic tion of isolated right heard. split- good prognosis found as a result of routine murmurs are frequently Physiological be ting almost excludes other causes of pulmonary electrocardiographic examination and can defect and suspected by hearing wide splitting of the first ejection murmurs such as atrial septal Thorax: first published as 10.1136/thx.36.2.95 on 1 February 1981. Downloaded from

A uscultation of the heart since Laennec 97 pulmonary stenosis. Moreover, the width of catheterisation, although there is at present no splitting (delay of P2) in pulmonary stenosis gives good non-invasive method for determining an assessment of severity of obstruction which is severity. almost as accurate as measurement of the There has been an improvement in our under- pressure gradient across the pulmonary valve.19 standing of diastolic murmurs with the advent Identification of a mitral opening snap is usually of echocardiography. 21 Ventricular filling mur- easy, particularly if a high frequency sound can murs without atrioventricular valve obstruction be heard or recorded in addition to the aortic are related to the semi-closing of the valve while and pulmonary components of the second heart forward flow is still continuing, the best example sound, but in difficult cases it can be identified by being the short mitral diastolic murmur in severe its coincidence with the opening halt of the mitral mitral regurgitation. Thus Austin Flint's observa- valve on echo. With calcific mitral stenosis, tions on the mechanism of the mitral diastolic particularly when complicated by severe pul- murmur in pure aortic regurgitation have been monary hypertension, abnormal sounds and mur- confirmed. 22 murs may be absent, and echocardiography is In conclusion, Laennec with his interest in needed. It is also useful when the diagnosis of diagnosis would have been gratified to know that mitral stenosis is difficult as in the presence of with careful history taking, followed by physical aortic stenosis and, of course, it has proved far examination of the cardiovascular system, a and away the most sensitive method for diagnosing correct diagnosis can be made in the majority of when auscultatory signs are non-specific. cases. Indeed with the additional aid of an electro- cardiogram, a radiograph of the chest, and an Heart murmurs echocardiogram, complicated invasive investiga- tions are seldom necessary except in neonatal The division of heart murmurs into pan- diagnosis and as a prelude to cardiac . systolic regurgitant murmurs and mid-systolic ejection murmurs seems to have stood the test of References copyright. time, provided that the murmur is analysed in relation to the relevant component of the second 1 McKusick VA. Cardiovascular sound. London: sound.20 For example, the pan-systolic murmur of Bailliere Tindall and Cox, 1958. mitral regurgitation engulfs A2 but stops before 2 Leatham A. Splitting of the first and second

heart sounds. Lancet 1954; 2:607. http://thorax.bmj.com/ P2; if splitting is wide because of shortening of 3 Haber E, Leatham A. Splitting of heart sounds left ventricular systole, this may give a false im- from ventricular asynchrony in bundle branch pression of an ejection murmur. In severe mitral block, ventricular ectopic beats, and artificial regurgitation there is a great shortening of left pacing. Br Heart J 1965; 27:691. ventricular ejection, A2 may be very early, and 4 Luisada A. "Tricuspid" component of the first occasionally an echo is needed for its identifica- heart sound. In Monograph No 46 of Am Heart tion. A with a synchronous Assoc, 1975. carotid pulse is often useful for analysing an 5 Crews T, Pridie R, Benham R, Leatham A. Auscultatory and phonocardiographic findings in obscure apical systolic murmur to get its relation- Ebstein's anomaly: correlation of first heart sound on September 28, 2021 by guest. Protected ship to the components of the second sound. It is with ultrasonic recordings of tricuspid valve move- particularly useful in the diagnosis of hypertrophic ment. Br Heart J 1972; 34:681. cardiomyopathy with a systolic murmur from 6 Leatham A, Leech G. Observations on the rela- obstruction to left ventricular outflow which tionship between heart sounds and valve move- tends to continue nearly to the aortic component ments by simultaneous echo and phonocardi- of the second heart sound, but there is a gap ography. Br Heart J 1975 (abstr); 37:557. shown on the phonocardiogram between the end 7 Waider W, Craige E. First heart sound and ejec- of the murmur and A2. Differentiation between tion sounds: echocardiographic and phonocardi- aortic valve and infundibular obstruction can ographic correlation with valvular events. Am J Cardiol 1975; 35:3. usually be made by noting the presence or absence 8 Brooks N, Leech G, Leatham A. Factors re- of an ejection sound. Echocardiography usually sponsible for normal splitting of first heart sound. can confirm the site of the obstruction and, in High speed echophonocardiographic study of experienced hands, gives some indication of the valve movement. Br Heart J 1979; 42:695. degree of calcification, if any. Thus the cause of 9 Wolferth C, Margolies A. Certain effects of auri- an obscure outflow systolic murmur can be cular systole and the prematurity of beat on the elucidated without the need to resort to cardiac intensity of the first heart sound. Trans Assoc Thorax: first published as 10.1136/thx.36.2.95 on 1 February 1981. Downloaded from 98 Aubrey Leatham Am Phys 1930; 45:44. 16 Leech G, Mills P. Leatham A. The diagnosis of 10 Levine S, Harvey W. Clinical auscultation of the a non-stenotic bicuspid aortic valve. Br Heart J heart. Philadelphia: WB Saunders, 1949. 1978; 40:941. 11 Burgraaf GW, Craige E. The first heart sound in 17 Mills P, Leech G, Davies M, Leatham A. The complete heart block: phonechocardiographic cor- natural history of a non-stenotic bicuspid aortic relations. Circulation 1974; 50:17. valve. Br Heart J 1978; 40:851. 12 Leatham A. Auscultation of the heart and phono- 18 Leech GJ, Davies MJ, Brooksby I. Parker cardiography. Second edition. J, London: Churchill Braimbridge MV. The use of M-mode echocardi- Livingston, 1975. ography to determine the pathogenesis of aortic 13 Leech G, Brooks N, Green-Wilkinson A, Leatham regurgitation. Br Heart J 1978; 40:460. A. Mechanism of influence of P-R interval on loudness of first heart sound. Br Heart J 1980; 19 Leatham A, Weitzman D. Auscultatory and 43:138. phonocardiographic signs of pulmonary stenosis. 14 Brooks N, Leech G, Leatham A. Complete right Br Heart J 1957; 19:303. bundle branch block. Echophonocardiographic 20 Leatham A. Auscultation of the heart: Goul- study of first heart sound and right ventricular stonian lecture. Lancet 1958; 1:757. contraction times. Br Heart J 1979; 41:637. 21 Fortuin NJ, Craige E. Echocardiographic studies 15 Mills P, Leech G, Leatham A, Ginks W. Non- of genesis of mitral diastolic murmurs. Br Heart invasive estimation of pulmonary end- J 1973; 35:75. diastolic pressure. Circulation 1975; 51 52 suppl 22 Fortuin NJ, Craige E. On the mechanism of the II:192. . Circulation 1972; 45:558. copyright. http://thorax.bmj.com/ on September 28, 2021 by guest. Protected