[On the genesis of the first heart sound: phono-echocardiographic study in patients with A-V block (author's transl)].

A phono-echocardiographic study of acustic and morphologic events was performed in three patients with atrioventricular block in order to assess the role of the mitral valve in the changes of the amplitude of the first heart and, more generally, in the genesis of the first heart sound. Simultaneous recording of the electrocardiogram, the apical phonocardiogram and the mitral echocardiogram showed: 1) the coincidence between the C point of the echocardiogram and the onset of the earlier high frequency vibrations of the first heart sound (M1); 2) a close correlation between the intensity of the first heart sound and the position of the mitral valve at the onset of ventricular systole (P less than 0.001); 3) longer duration of the first heart sound in those beats when there was superimposition of P wave in QRS. The authors illustrate the recent reports about the genesis of the first heart sound and emphasize the main role of the mitral valve suggesting that the position of the mitral leaflets at the onset of ventricular systole influences the mechanism of acceleration and deceleration of blood and vibrations of the "cardiohemic system".