The genesis of gallop sounds: investigation by quantitative phono- and apexcardiography.

Abstract

The genesis of gallop sounds was investigated in 12 patients by simultaneous measurement of external apexcardiographic (ACG) and left ventricular (LV) pressure, dP/dt [change in pressure over time] and sound using infinite time constant piezo-resistive pressure transducers with identical sensitivity and frequency responses. Absolute intensity of internal and external sound was quantified. The external transducer was applied to the chest wall with a pressure of 200-400 mm Hg. Six patients had a 3rd heart sound (S3), 8 had a 4th heart sound (S4) and 1 patient had a summation gallop. Left atrial (LA) pressure, dP/dt and sound were recorded in one S3 and 4 S4 patients. The dP/dt of the rapid filling wave (RFW) and a wave of both apexcardiogram and left ventricle were measured. Similar data were obtained in 10 control patients without gallop sounds. The intensity of gallop sounds was uniformly greater over the chest wall than inside the left ventricle or left atrium. The dP/dt of RFW and a wave tended to be higher in the apexcardiogram than the left ventricle of control patients. The dP/dt of the LV RFW IN S3 patients and a wave in S4 patients tended to be higher than those in control subjects, but there was overlap. The dP/dt of ACG filling waves in patients with gallop sounds was significantly greater (P < 0.01) than the respective filling wave of the left ventricle. The ACG dP/dt of the RFW in all S3 patients and a wave in all S4 patients was increased above the maximal values of the respective ACG filling waves in the control subjects. The higher intensity of gallop sounds and the higher dP/dt of the filling waves over the chest cannot be caused by passive transmission of sound or pressure changes in the left ventricle. The greater vibratory energy of gallop sounds recorded over the precordium apparently is caused by the impact of the heart on the chest wall. The strength of the impact is a function of several interacting mechanisms, including the momentum transfer and coupling between the heart and the chest wall.