The First Heart Sound in Ventricular Contractions Arising from the Apex and Base. ∗

Abstract

Summary

1. Simultaneous electrocardiograms and phonocardiograms were recorded from 5 human subjects having ectopic ventricular systoles. Similar tracings were obtained from 5 dogs in which ectopic systoles were produced by induction shocks to the exposed heart during vagal arrest. The time interval between beginning of ventricular depolarization and onset of the first heart sound was measured for normal and for ectopic beats. The data were subjected to statistical analysis. 2. The beginning of the first heart sound was significantly delayed in ectopic ventricular contractions. The first sound occurred significantly later in ectopic beats arising from the ventricular base than in those from the apex. The probable reasons for these findings are discussed.