HEART TRANSPLANT

medical procedure involving the removal of a diseased heart from a patient with heart muscles damaged beyond surgical repair and its replacement with a sound heart, usually from a person who has just died. Because of the immense complexity of the operation and the difficulty of finding appropriate donors, heart transplant is performed only as a last resort in patients whose projected survival with their own heart is only a few weeks or months. In most cases, transplanted hearts are taken from persons who have suffered irreversible brain damage and been declared legally dead. Norman E. Shumway achieved the first successful heart transplant in a dog at Stanford University, Calif., U.S., in 1958. He spent the next decade conducting laboratory research to refine the technique and improve immune suppression in the animal model. On Dec. 3, 1967, Christiaan Barnard of South Africa performed the first human heart transplant at Groote Schuur Hospital, Cape Town. His success was followed by attempts at many other medical centres; 101 heart transplants were undertaken around the world within the next 12 months. Problems with immune rejection of the transplanted heart, poor patient survival, and concern about the assignment of enormous resources to an experimental technique of limited applicability led most surgeons to abandon the procedure after the initial attempts. Shumway, Barnard, and some others, however, continued to perform heart transplants, developing methods that significantly improved patient survival to the point that more than 50 percent of all patients lived at least five years after surgery. Many of these patients were able to lead productive lives for eight years or more after the operation. As a result of these successes, interest in heart transplants revived somewhat, and several medical centres were again attempting them. The current procedure involves removal of the diseased heart except for some of the tissue from the atria, the two upper chambers of the heart. Leaving this tissue in place preserves nerve connections to the sinoatrial node, a patch of electroconductive tissue that regulates heartbeat. The replacement heart is removed from the donor and preserved in a cold salt solution. During implantation it is trimmed to fit and sutured into place, making all necessary vascular connections. Great care is taken to match patients and donors as to blood type and other immunologic indicators, but the body's natural immunity must be suppressed to prevent transplant rejection. Drugs such as prednisone or antithymocyte globulin that inhibit a major group of immunoprotective cells are used for this. Anticoagulants are also administered to prevent atherosclerosis (hardening of the arteries) in the transplanted heart, a problem that caused the death of many early transplant patients.