Present status of human cardiac allografts and prospects for xenografts

Cardiac allotransplantation is no longer experimental. It is the standard by which all other methods of cardiac replacement must be judged. The dramatic improvement in survival and the quality of life of cardiac transplant recipients reflects many factors including refined criteria for patient and donor selection, as well as the clinical introduction of cyclosporine. Current contraindications to the procedure include: 1) age greater than 65 years, 2) active infection, 3) active malignant neoplastic disease, 4) recent pulmonary embolus or infarction, 5) irreversible renal or hepatic failure, and 6) fixed elevation of pulmonary vascular resistance. The introduction of cyclosporine has been accompanied by an increase in the 1 year survival. While the use of cyclosporine has not decreased the incidence of rejection episodes, it has dramatically decreased their severity. In addition, the incidence and severity of infectious complications, as well as the length of hospitalization, have been decreased with the introduction of cyclosporine. Despite the progress made, several problems remain in the management of transplant recipients. Chronic cyclosporine therapy has been associated with a disturbingly high incidence of hypertension and renal impairment, and a low, yet significant, incidence of malignant neoplasms. However, the most significant obstacle to successful clinical cardiac transplantation is the scarcity of donor organs. Many centers now report that the mortality rate for patients awaiting transplantation exceeds the mortality associated with the procedure itself. Donor scarcity has led to renewed interest in the development of mechanical cardiac devices and investigation into cross-species transplantation (xenotransplantation).