The OregonHeart Total Artificial Heart: Design and Performance on a Mock Circulatory Loop

Widespread use of heart transplantation is limited by the scarcity of donor organs. Total artificial heart (TAH) development has been pursued to address this shortage, especially to treat patients who require biventricular support. We have developed a novel TAH that utilizes a continuously spinning rotor that shuttles between two positions to provide pulsatile, alternating blood flow to the systemic and pulmonary circulations without artificial valves. Flow rates and pressures generated by the TAH are controlled by adjusting rotor speed, cycle frequency, and the proportion of each cycle spent pumping to either circulation. To validate the design, a TAH prototype was placed in a mock circulatory loop that simulates vascular resistance, pressure, and compliance in normal and pathophysiologic conditions. At a systemic blood pressure of 120/80 mm Hg, nominal TAH output was 7.4 L/min with instantaneous flows reaching 17 L/min. Pulmonary artery, and left and right atrial pressures were all maintained within normal ranges. To simulate implant into a patient with severe pulmonary hypertension, the pulmonary vascular resistance of the mock loop was increased to 7.5 Wood units. By increasing pump speed to the pulmonary circulation, cardiac output could be maintained at 7.4 L/min as mean pulmonary artery pressure increased to 56 mm Hg while systemic blood pressures remained normal. This in vitro testing of a novel, shuttling TAH demonstrated that cardiac output could be maintained across a range of pathophysiologic conditions including pulmonary hypertension. These experiments serve as a proof-of-concept for the design, which has proceeded to in vivo testing.