Cardiac prosthesis as an advanced surgical therapy for end-stage cardiac patients: current status and future perspectives.

Abstract

This paper reviews the current status and future perspectives of the artificial heart research that was started in 1957 by Akutsu and Kolff. During the 1960's, although not much progress was made in increasing animal survival time with artificial hearts, clinical applications were already made for both a ventricular assist device in 1962 and total artificial heart (TAH) in 1969 followed by a second TAH application in 1981. Both TAH applications were done as bridges to heart transplantation. Meanwhile, the animal survival time improved during the 1970's because of the availability of better biomaterials, better understanding of the circulatory system, and improvement in surgical techniques. Continuous flow pumps were also investigated during the 1970's, which demonstrated feasibility for chronically supporting circulation in healthy animals. Four permanent cases of TAH application were done early 1980's for patients who could not be the candidates for heart transplantation. Although the patients were tethered to the external drive-console, one of them survived for nearly two years. Complications due to thromboembolism and infection were the major causes of death in these patients. The patients' quality of life was questionable and the permanent application of the TAH was then stopped to make improvements in the system in terms of implantability and biocompatibility. During the 1980's, efforts were then switcthed to development of totally implantable VAD and TAH systems, which led to the first discharge of a VAD patient from the hospital in 1992. In the early 1990's, implantable electric VADs, Novacor and ThermoCardio System (TCI), became available to support the circulation of end-stage cardiac patients until a donor heart could be found. The transplantation rate of the VAD patients ranged around 70% with the average waiting time of 80 to 100 days. The number of patients transplanted with VADs are more than 5000 and those with the pneumatic TAH exceed 200. Because of the larger size, requirement of heart valves, and complicated control mechanism of the pulsatile VADs, continuous flow pumps have been gaining popularity among clinicians. The clinical applications of the continuous flow devices have just begun, demonstrating remarkable performance in bridging to heart transplantation. In, the 21st century, we will see prevalent clinical applications of various circulatory support devices from pulsatile VAD, pulsatile TAH to continuous flow VAD. These devices will be combined with genetic treatment to re-generate the myocardium and recover the failing heart. Complete recovery of the myocardium may become possible through therapy combining circulatory assist devices and biotechnology.