Influence of the timing of atrial systole on mitral valve closure and on the first heart sound in man

Abstract

Simultaneous recordings of electrocardiogram, phonocardiogram, indirect carotid pulse and pulsed ultrasound cardiogram of the anterior mitral leaflet were obtained in patients with heart block. In patients with compensated heart failure and heart block, the timing of mitral valve closure was a function of the timing of atrial systole for all beats with an effective diastolic P wave and a P-R interval greater than 0.2 second. Once closed, the mitral valve stayed closed through the remainder of diastole. In 1 patient with acute left heart failure, diastolic P waves did not result in mitral valve closure. The amplitude of the first heart sound was closely related to the timing of mitral valve closure. The mitral valve closure in diastole was silent, and the subsequent first sound was small. When the valve closed in early systole, the amplitude of the first sound was related to the rate and amplitude of the valve closure movement. The timing of mitral valve closure in relation to the left ventricular pressure pulse may be the important determinant of production of the first sound.