HEMODYNAMIC RESPONSE TO EXERCISE AFTER PROPRANOLOL IN NORMAL SUBJECTS

Abstract

Supine exercise after beta-adrenergic blockade with propranolol in six normal subjects caused (a) a mean decrease of 13% in resting heart rate; (b) a mean decrease of 20% in resting cardiac output; (c) a mean reduction of 17% in exercise cardiac output and a mean reduction of 21% in exercise pulse rate; (d) a decrease in the elevation of arterial systolic pressure produced by exercise; (e) an increase in exercise end-diastolic pressures in the left ventricle and in exercise pulmonary artery pressures; (f) more rapid recovery of circulatory function after exercise. There was no consistent change in pulmonary vascular resistance. Even though the normal cardiac response to exercise would seem to be dependent on intact beta-adrenergic receptors, the exercise loads chosen were completed just as easily after the blockade as before.