Mechanical vibration transmission characteristics of the left ventricle: implications with regard to auscultation and phonocardiography

Systolic-diastolic phasic alteration of left ventricular mechanical vibration transmissibility was studied in an open chest canine preparation. A continuous vibratory tone was applied to the base of the heart, and a miniature heart surface vibration sensor applied to the epicardium near the ventricular apex. This allowed the detection of the percent of the vibration that was transmitted from source to sensor. These data were compared with those from intracardiac phonocardiograms obtained using a micromanometer-tipped catheter. It was found that in systole, the ventricle transmitted a vibratory tone from the cardiac base to the apex so that it was readily detected by the heart surface sensor. In marked contrast, during diastole the relaxed ventricle failed almost completely to transmit the vibration to the apical position. When the dog experienced heart failure during hypoxia, the ventricular diastolic vibration transmissibility was found to equal or exceed that of the systolic phase.