Hemodynamic correlates of the third heart sound

Abstract

The third heart sound was related to hemodynamic events in 18 dogs using both external and intracardiac phonocardiograms, multiple catheterizations, and additional techniques. The third sound was found to be independent of atrioventricular or ventriculoatrial pressure gradients. The time of occurrence of the third sound was determined within certain limits by the duration of isovolumetric relaxation, which showed a definite rate dependency. The third heart sound persisted under conditions in which blood flow into the ventricle was prevented. The third heart sound coincided constantly with the return to the base line of the first derivative of the intraventricular pressure curve. Based on its independence from flow in marked systolic overload and on its relationships to parameters reflecting the state of the myocardium it seems that the third sound is associated with the end of ventricular muscle relaxation when ventricular volume and compliance equilibrate.