CLEVELAND CLINIC NIMBUS TOTAL ARTIFICIAL-HEART - DESIGN AND IN-VITRO FUNCTION

We describe the design and in vitro testing of the Cleveland Clinic-Ni mbus electrohydraulic permanent total artificial heart as it nears com pletion of development. The total artificial heart uses an electric mo tor and hydraulic actuator to drive two diaphragm-type blood pumps. Th e interventricular space contains the pump control electronics and is vented to an air-filled compliance chamber. Pericardial tissue valves and biolized blood-contacting surfaces potentially eliminate the need for anticoagulation. In vitro studies on a mock circulatory circuit de monstrated preload-sensitive control of pump output over the operating range of the blood pump: 70 to 160 beats/min and 5 to 9.6 L/min at ri ght and left atrial pressures of 1.0 to 7.0 mm Hg and 5.0 to 12.0 mm H g, respectively. The pump output was found to be insensitive to afterl oad over a range of 15 to 40 mm Hg mean pulmonary artery pressure and 60 to 130 mm Hg mean systemic pressure. The left master alternate cont rol mode balanced the ventricular outputs during simulated bronchial a rtery shunting of up to 20% of cardiac output. A 10% to 15% right-pump , stroke-volume limiter balanced ventricular outputs during maximum ou tput of 9.6 L/min. In response to a sustained increase in systemic ven ous return, the pump increased output by 2 L/min (29%) in 35 seconds. Thus the Cleveland Clinic-Nimbus total artificial heart meets the Nati onal Heart, Lung, and Blood Institute hemodynamic performance goals fo r devices being developed for permanent heart replacement. The biolize d blood-contacting surfaces should decrease the risk of thromboembolis m associated with circulatory assist devices.