THE NATURE OF THE S COMPLEX OF THE ELECTROCARDIOGRAM

Abstract

The downstroke of S3 develops with the complete activation of the posterior surface of the left ventricle while a portion of the anterior surface of the right ventricle is not yet active. The upstroke of Ss occurs when the remainder of the anterior surface of the right ventricle becomes active and restores isopotentiality. The same sequence of ventricular excitation explains the presence of an S3 in the ventricular extrasystole. S1 probably arises from a similar sequence of excitation in the anterior left and posterior right ventricles.