Totally implantable artificial organ: cardiac prosthesis.

This article reviews the current status of completely implantable cardiac prostheses, with an emphasis on those systems presently under development at The Cleveland Clinic Foundation (CCF). Such devices have been one of the final goals of artificial heart research since 1957, when Dr. Kolff initiated these studies in Cleveland. Although earlier plans aimed at using radioisotopes as the energy source, more recently, due to public opinion and sociopolitical influences, the shift has been towards exclusive use of electrically activated energy converters. These systems can be roughly broken down into two groups according to the powertrain configuration. In the first group, electric heating coils maintain liquid salts in thermal batteries at temperatures close to 500 degrees C. This thermal energy is then converted (through a Stirling cycle) to mechanical motion of the pusher plate (PP) which in turn acts on the blood. Two such systems (emphasized in this article) are under development here at CCF in joint efforts with Nimbus Corporation and the University of Washington, respectively. In the second group of ventricular assist systems, electric energy is converted directly to PP motion through rotating cams, solenoids, or electrohydraulic transmission systems. At least four American contractors are working at the preclinical stage on this group of devices. One in particular, the CCF-Nimbus system, consisting of a biolized surface blood pump, an electrohydraulic energy converter, and a compliance chamber to handle the variable volume behind the PP, is described in depth in this discussion. In terms of future prospects, it is forecasted that by 1988, the completely implantable VAS will be used clinically, and that by 1994, a specially designed total artificial heart (nontethered patient) would be ready for human use.