Mechanical circulatory support until heart transplantation

Abstract

The increased use of heart transplantation as a means of treating patients with terminal cardiac insufficiency has caused a steady increase in the number of transplantation candidates on waiting lists. The availability of suitable donor organs has not been able to keep pace with this development, such that a growing number of potential recipients do not survive until transplantation (21). Progressive myocardial insufficiency and sudden cardiac arrest as a result of malignant rhythm disturbances, the latter of which is preventable through the implantation of an automatic defibrila- tor (AICD) (3), represent the main causes of death of patients on the waiting list. These patients can be acutely helped through the implantation of a mechanical circulatory support system. Besides their immediate life-saving function, such systems can also help patients who begin to develop increasing functional disturbances in other organ systems because of protracted circulatory failure to attain a condition more favorable to the success of the transplantation. In this manner the donor organs available can then be transplanted under more favorable conditions. Both an American multi- center study on the use of the TCI left ventricular support system as well as experience with the Novacor system were able to show that survival until transplantation as well as survival after transplantation were markedly better in the group of mechanically supported recipients than in a medicamentously treated control group (Fig. 1) or in the register of the International Society for Heart Transplantation (Fig. 2). Our experience has shown that some transplantation candidates experience such a remarkable recovery in cardiac function during long-term unloading that the mechanical system could be explanted since the patients had attained a level of physical vigor which was significantly better than their previous condition (see below). All of these observations invalidate the old argument that the use of mechanical support systems would only exacerbate the shortage of donor organs. The knowledge gained through mechanical bridging to transplantation experience proves that it is possible to provide patients effective permanent support with artificial heart systems as a real alternative to transplantation. This aspect is discussed in greater detail in the chapter on artificial hearts.