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Genesis of high frequency heart sounds.

Sir, The recent paper by Trail et al. (Br Heart J 1982; 48: 78-80) provides interesting support for the valvular genesis of high frequency heart sounds. As was shown by Mills et al.,I we were able to record a diastolic heart sound simultaneously with echocardiographc mitral valve closure in a "normal" patient with congenital heart block. The intensity of such sounds, however, never reached the level of the true normal mitral component of the first sound. As Traill suggests, that intensity can occur only if there is an abrupt rise in ventricular diastolic pressure inducing sudden termination of forward flow across the mitral valve, but that means also the establishment of an increasing pressure gradient across the mitral valve enhanced by the atrial relaxation. In our own study,2 we have assessed the timing of the mitral component of the first sound with the simultaneous recording of echocardiographic mitral valve closure and the apex cardiogram and its first derivative, the latter giving a good estimate of the variation of left ventricular wall tension and thus of left ventricular pressure.3 We found a very close correlation between the mitral component of the first heart sound and mitral valve closure, and, as Luisada et al. 45 had previously shown there was a correlation with the left ventricular pressure derivative, and a lesser but highly significant correlation between mitral valve closure and the first peak of the apex cardiogram derivative. Therefore, like Palfrey,6 we suggest a valvulomuscular theory in the genesis of high frequency heart sounds. These sounds occur after valvular coaptation at the time of maximum tension: their loudness is a direct function of the rate of the developed pressure gradient across the valve just before coaptation through active (contraction) and passive (relaxation) myocardial mechanisms. This theory also enables us to explain the existence of a loud diastolic mitral component of the first sound in the particular case of Traill, the simultaneous recording of the apex cardiogram showing clearly the very sharp combined rapid filling wave well related to the fourth sound and ended by an unusual notch clearly time related to mitral valve closure and the mitral component of the first heart sound. That notch is evidence of a pressure transient caused by abrupt cessation of inflow.