Effects of Adrenergic Stimulation on Systolic Time Intervals in Patients with Artificial Pacemaker

Abstract

The aim of this research was to contribute for a better knowledge of the physiological determinants of the temporal dynamics of the left ventricular chamber contraction. We have studied the effects of adrenergic stimulation on systolic time intervals in patients with artificial pacemaker (PM). These subjects are of considerable pathophysiological interest representing an useful experimental model; compared with subjects with spontaneous electrical activity, patients with PM present: l) a fixed heart rate or only slightly modified heart rate; 2) frequent occurrence, within short time intervals, of systoles with different electrogenesis; 3) abnormal intraventricular conduction. In previous papers[1–5] we have employed the study of systolic time intervals in the pathophysiological investigation of patients with PM; the present report deals with results of a study on the effect of microdoses of epinephrine on systolic time intervals in patients with demand pacemaker presenting, at the time of the study, systoles of different electrogenesis. The microdoses of epinephrine employed may be considered “metabolic”, not unlike the amounts secreted in physiological conditions and without hypertensive effect upon the systemic circulation[6–10].