Ventricular changes associated with sympathetic augmentation of cardiovascular pressure pulses

¹ Department of Physiology, Stritch School of Medicine and Graduate School, Loyola University, Chicago, Illinois

Electrical excitation of the sympathetic innervation of the heart elicits marked increase in force of contraction of both ventricles which in turn produce augmented arterial pressure pulses. These pulses are characterized by a shortened isometric contraction period, a steeper rise in the systolic ejection phase, and a relatively greater rise in systolic than in diastolic pressure. Cardiometer tracings reveal an increase in both the rate and volume of systolic ejection, smaller end-systolic volume, with no significant change in end-diastolic volume. Stimulation during isovolumetric conditions in the ventricles reveals that such augmentation is primarily dependent upon changes in contraction of the myocardium and not upon alterations in peripheral resistance or in initial distention of the ventricles. Augmentation of systemic arterial pulses is immediately sustained by appropriate adjustments in venous return from the pulmonary vascular bed. Prolonged augmentation demands similar adjustments in venous return to the right heart and the pulmonary bed.