Abstract
Effects of experimental ventricular pacing on ventricular function were studied on 5 anesthetized dogs. The heart was stimulated by bipolar electrodes placed at the right atrial appendage and the epicardium at the apex or base of the left ventricle. Cineangiocardiographic analysis of the left ventricle was made and the sequential change in the shape of the left ventricle during ventricular contraction was compared among each of three stimulation sites.
A systolic expansion of the localized area of electrical stimulation was observed during stimulation at the base as well as at the apex of the left ventricle, but not during right atrial stimulation, and it was consistently reproducible in any given experiment. Correlation of individual cine frames to simultaneously recorded ventricular pressures revealed that the bulge developing in mid-systole reached its maximum size at the end of the ventricular ejection period and disappeared during the period of isovolumic relaxation of the ventricle.
