IN-VITRO AND IN-VIVO HEAT DISSIPATION OF AN ELECTROHYDRAULIC TOTALLY IMPLANTABLE ARTIFICIAL-HEART

The authors evaluated the heat transfer characteristics of an electroh ydraulic totally implantable artificial heart (EH-TAH) developed at ou r institute. In three in vitro experiments, the heat dissipation of th e EH-TAH was investigated. First, the EH-TAH was connected to a closed mock circuit filled with 1 L of saline, and driven at an input power of 20 W. The estimated heat conducted to the blood was similar to 10.3 W, which was almost half of the input power. Second, we simulated hea t transfer with the circulation of a calf by using a heat exchanger. T he amount of heat dissipating directly from the EH-TAH surface was cal culated to be 10 W. Third, the temperature of the actuator examined wi th thermography was found to be almost uniform, and no prominent high temperature area was observed. In an in vivo study, the EH-TAH was imp lanted for 10 days in a calf weighing 62 kg. The input power was 18 +/ - 2 W, the temperature of the actuator-tissue contacting surface was 3 9.5 +/- 0.8 degrees C, and that of the pump blood chamber was 39.8 +/- 0.4 degrees C. This slight temperature elevation was thought to be at tributable to heat dissipation to the blood. On histologic study of th e chest wall and the lung in contact with the actuator, vascularized c onnective tissue envelopes were observed, but unfavorable side effects , such as tissue necrosis, were not observed. These results suggest th at the thermal effect of this system is acceptable at the input power used.