Current status of development and in vivo evaluation of the National Cardiovascular Center electrohydraulic total artificial heart system

Abstract

We have been developing an electrohydraulic total artificial heart system. The system has a pumping unit, consisting of diaphragm-type blood pumps and an energy converter, and an electronics unit, consisting of an internal controller, an internal battery, and transcutaneous energy transfer and optical telemetry subunits. The energy converter, designed to be placed outside the pericardial space, reciprocates and delivers hydraulic silicone oil to the alternate blood pumps through a pair of flexible oil conduits. The left-right output balance is achieved with an interatrial shunt made in the composite atrial cuff. In vivo performance of the pumping unit has been evaluated by chronic implantation of 16 calves weighing 54–88 kg. Five calves survived for more than a week, and the longest-surviving animal lived for over 12 weeks until its accidental death. In this animal, a cardiac output of 6–81/min was maintained by the device with power consumption of 13.5±0.9W and 9%–11% efficiency. The left and right atrial pressures were 16±4 and 14±4 mm Hg, respectively, and the left-right output difference was adequately balanced with the interatrial shunt. The mixed venous oxygen saturation was 65±6% and the serum lactate level was 5±1 mg/dl, representing favorable oxygen metabolic conditions. The temperatures of the energy converter and the blood pump surfaces were 39.4±0.7° and 38.8±1.5°C, respectively, indicating that heat generation and dissipation were acceptable. The serum and tissue silicon levels were within normal (<1 μg/ml or <1 μg/g), indicating that permeation of silicone oil through the blood pump diaphragm was inconsequential and unlikely to be detrimental. We conclude that the system has the potential to be a totally implantable cardiac replacement.