Splitting of second heart sound in patients with aortic regurgitation.

The intervals between the two components of the second heart sound (A2-P2), measured from the phonocardiograms of 50 patients with severe aortic regurgitation, were compared with those of 57 normal subjects. During expiration the second sound was single or closely split in both groups. Inspiratory augmentation of the A2-P2 interval of less than 0.02 sec occurred in one normal subject (2%) and in 42 patients with aortic regurgitation (86%). Thus the great majority of patients with severe aortic regurgitation had either a single or a closely split second heart sound during both phases of respiration. The mean Q-A2 intervals (rate corrected) of 30 patients, in whom severe aortic regurgitation was documented by contrast angiographic studies, were longer than those of normal subjects during both phases of respiration, and the difference was statistically more significant (P < 0.02) during inspiration. Thus prolongation of the Q-A2 interval was the main factor responsible for the disappearance of the normal asynchrony of semilunar valve closure, in patients with aortic regurgitation.