Mechanical circulatory support devices for bridge to heart transplantation, bridge to recovery, or destination therapy

Both the ventricular assist device (VAD) and the total artificial heart (TAH) have been effective in supporting circulation of end-stage cardiac patients and in bridging to heart transplantation. However, because of a shortage of donor hearts and age limitations, destination therapy with the completely implantable VAD has also been started. The totally implantable TAH in the United States is in the final stage of development and will go into preclinical trials in 2004. In Japan, heart transplantation has been re-instituted since last year, but because of shortages of donor hearts the waiting time prior to transplantation is fairly long. To date, six heart transplantations have been carried out, of which four have been bridged transplantations using extracorporeal or implantable VADs. With the extracorporeal VADs, patients cannot be discharged home, which increases the hospital expenses. With the implantable VADs such as Novacor and HeartMate imported from the USA, patients can be discharged home, but major threats with these devices are thromboembolic complications and infection. These devices are also fairly large, being designed for 80-kg patients, and are thus difficult to implant in patients of 50 to 60kg, including women. Because of these limitations, there is a strong clinical demand for a compact, high-performance, implantable, permanent-use VAD. This paper addresses the current status of the artificial heart research and development program at the Tokyo Medical and Dental University, which was started in May 1999.