Hemodynamic response to exercise in the unanesthetized calf with pulseless arterial flow.

In a chronic unanesthetized calf model with a centrifugal pump inserted from left ventricle to aorta, calves were trained to perform treadmill exercise and undergo hemodynamic measurements. Resting hemodynamic changes with pulseless pumping included increases in cardiac output, aortic pressure, and heart rate, with some decrease in systemic vascular assistance. Treadmill exercise was associated with further increases in cardiac output and heart rate, which progressively increased during the 10 days of observation, with little change in mean aortic pressure. Pump autoregulation responded to the decreased systemic vascular resistance associated with exercise by increasing pump output about 15%, at constant pump rotatory speed. These experiments add further evidence regarding the ability of a centrifugal left ventricular assistance system to support the failing heart and to permit moderate degrees of exercise in the intact unanesthetized calf.