The first heart sound and the dynamic events in ventricular ectopic beats and in paced beats

Abstract

The electrocardiograms and clinical phonocardiograms of 27 patients presenting ventricular ectopic beats were studied, as well as the electrocardiograms, intracardiac phonocardiograms and pressure tracings from both ventricles of 11 patients presenting ventricular ectopic beats during catheterization. The electrocardiograms and clinical phonocardiograms plus the carotid tracings of 5 patients with artificially paced hearts were also studied. It was demonstrated that both the ectopic origin of the impulse and pacing prolong the interval between the onset of the QRS complex and the first heart sound (QRS-I interval) and that right ventricular ectopic origin or right ventricular pacing prolongs this interval more than left ventricular ectopic origin or left ventricular pacing. These facts are discussed and related to (1) altered modality of left ventricular activation (ventricular ectopic beats, paced beats); and (2) additional delay in left ventricular contraction occurring in the case of either right ventricular ectopic beats or hearts paced from the right ventricle, because the left ventricle is the only chamber that causes the first heart sound. No difference was found in the interval between the first two components of the first sound.