Continuous-flow total artificial heart supports long-term survival of a calf

The development and clinical use of continuous-flow left ventricular assist devices (LVADs) stimulated our interest in developing a total heart replacement with continuous-flow rotary blood pumps. We constructed a continuous-flow total artificial heart (CFTAH) from 2 HeartMate II axial-flow LVADs and used this CFTAH to replace the native heart of a calf. The purpose of this experiment was to study the effects of total continuous flow on physiologic parameters at rest and during exercise after the animal recovered from surgery. We monitored pulmonary and systemic pump performance, and we assessed arterial blood gases, hemodynamic and biochemical variables, and neurohormone levels during the 7 weeks of CFTAH support. At day 36 after CFTAH implantation, the calf was exercised on a treadmill at increasing speeds for 40 minutes; total oxygen consumption, pump flow, blood pressure, and respiratory rate were monitored. Baseline hematologic levels were altered postoperatively but returned to normal by 2 weeks. We saw no signs of hemolysis or thrombosis during CFTAH support. The calf had a normal physiologic response to treadmill exercise. The animal gained weight and appeared to function normally during the study. The CFTAH operated within design specifications throughout the study. Homeostasis, end-organ and vasomotor function, and the ability to exercise are not adversely affected by 7 weeks of totally pulseless circulation in a calf.