Studies related to development of an implantable power source for circulatory assist devices

If available, a totally implantable circulatory support system would be invaluable in the management of patients with severe myocardial disease. It has been calculated that the pumping power required for such a system in a typical patient ranges from 1 to 6 watts, with an average of 1.75 watts. Three alternate approaches to the development of an implantable system capable of meeting this power requirement are presented and evaluated. The biologic fuel cell is attractive in principle, but significant advances in technology are essential to the development of a practical device. Rechargeable battery systems may not meet reliability requirements and are heavier than desired. The recommended approach consists of a miniature Rankine cycle reciprocating engine powered by a radioisotope energy source and containing a thermal energy storage cell to accommodate peak loads. An important consideration in totally implanted systems is the additional endogenous heat produced by the energy source. To evaluate this problem, an experimental model is described utilizing electrically energized heat exchangers implanted in dogs. Investigations to date suggest that the body should be able to dissipate this amount of heat, using normal physiologic mechanisms. Studies are continuing in order to establish conclusive results.