Relationship of Heart Sounds to Acceleration of Blood Flow

Abstract

A concept has been presented that abrupt acceleration or deceleration of blood flow is associated with an energy source sufficient to displace the mass of the heart, and that, consequently, this mass will oscillate at a sum of frequencies that are a function of chamber mass and restoring forces. Induced pressure transients may be observed in all chambers, the lower frequencies appearing on conventional pressure tracings, the higher frequencies as intracardiac sound. Using high frequency response instrumentation in dogs, intravascular sound has been compared with pressure and flow events throughout the cardiac cycle. (1) The first component of the first heart sound occurs during early isometric ventricular contraction and is associated with lower frequency pressure transients that may berecorded from all chambers of the heart. The left atrial "c-wave" is one of these transients. (2) The second component of the first heart sound occurs during ventricular ejection, and appears to be a function of acceleration of aortic blood flow. (3) The second heart sound begins significantly before aortic valve closure, while forward flow is still going on, and is proportional to the magnitude of deceleration of blood flow. (4) The third heart sound appears only in the presence of left ventricular failure at the time of rapid ventricular filling, and is associated with a low frequency wave recordable from the central aorta. The production of these transients is presumed to be deceleration of inflow as the limits of ventricular relaxation are reached. (5) A fourth sound arises coincident with pressure transients in other chambers as atrial systole further distends the left ventricle. It is proposed that acceleration and deceleration of blood flow is a sufficient and necessary condition for the origin of cardiovascular sound transients.