Abnormal diastolic mechanical vibration transmission characteristics of the left ventricle.

In 18 open chest canine experiments, the ability of the left ventricle to transmit a mechanical vibratory tone from base to apex has been studied. An artificial tone source of constant amplitude and frequency was applied to the base of the exposed left ventricle. A miniature vibration sensor was applied to the anterior epicardium near the ventricular apex. This permitted us to obtain a heart surface phonocardiogram, in order to detect the portion of the source vibration which was transmitted to the apex. In three of the dogs, the heart surface phonocardiogram from the apex was compared with simultaneous intraventricular phonocardiograms which showed the amplitude of the vibration which reached the intraventricular blood mass. It was found that the normal ventricle transmits the tone from base to apex almost exclusively during systole, when the ventricle is contracted and stiff. In marked contrast, the normally relaxed and soft ventricle fails almost completely to transmit the tone to the apex. In conditions of poor relaxation ability of the left ventricle due to global hypoxemia, manifested by a long "Time Constant T", an abnormal diastolic transmission of the tone to the apex occurred during early diastole. We have defined this abnormal early diastolic "crescendo-decrescendo" type of transmissibility as "Type 1". The Type 1 transmission is related to impaired relaxation of the ventricle and is a manifestation of one or more abnormal ventricular muscle properties, such as myocardial stiffness, viscosity and density. In conditions of left ventricular hemodynamic failure caused by global hypoxemia, a separate abnormal mid-to-late diastolic "crescendo" type of transmissibility was found, and is defined as "Type 2".(ABSTRACT TRUNCATED AT 250 WORDS)