CHRONIC NONPULSATILE BLOOD-FLOW .2. HEMODYNAMIC-RESPONSES TO PROGRESSIVE EXERCISE IN CALVES WITH CHRONIC NONPULSATILE BIVENTRICULAR BYPASS

We investigated the effects of stepwise treadmill exercise on animal ( calf) hemodynamic variables during chronic nonpulsatile biventricular bypass ,vith ventricular fibrillation, Seven days was allowed for reco very from the effects of anesthesia and surgery; each animal's natural heart was then fibrillated, The pump flows were maintained at nominal rates of 90, 100, and 120 ml . kg(-1). min(-1) for 1 week each, with the order varying from experiment to experiment. A total of 30 increme ntal exercise tests were performed on five animals, No significant cha nges in mean aortic pressure were observed during nonpulsatile perfusi on at the three nominal flow rates of nonpulsatile flow either before or during exercise, The systemic vascular resistance decreased signifi cantly during exercise (from 705 +/- 22 to 547 +/- 81 dyne . sec . cm( -5), p < 0.01, and from 604 +/- 25 to 510 +/- 15 dyne . sec . cm(-5) p < 0.05, at nominal flow rates of 100 and 120 ml . kg(-1). min(-1), re spectively), There were also significant (analysis of variance, Scheff e test, p < 0.05) differences in systemic vascular resistance among th ree nominal flow rates both before and during exercise, These results suggest that the autonomic nerve reflex control of the cardiovascular system in physical exercise was functioning normally in animals with c hronic nonpulsatile blood flow.