Indications and Procedures
Heart
transplantation is performed when congestive heart failure
or heart injury cannot be treated by other conventional medical or surgical means. It is reserved for patients with a high risk of dying within two years. The procedure involves removal of a diseased heart and its replacement with a healthy human heart or possibly an animal heart. In special cases, the surgeon may place the donor heart next to the diseased heart without removing it; this is called a piggyback transplant.
Patients who are candidates for heart transplantation include those with valvular disease, congenital heart disease, or rare conditions such as tumors. The selection of recipients is based on which patients are likely to exhibit the most pronounced improvement, functional capacity, and life expectancy after surgery. In the United States, the limited availability of donor hearts has necessitated the creation of a national organ procurement and distribution network called the United Network for Organ Sharing (UNOS), which distributes organs based on severity of illness, waiting time, donor and recipient blood types, and body size match.
Uses and Complications
The first human heart
transplantation was performed on December 3, 1967, by Christiaan Barnard in Capetown, South Africa. The heart transplantation procedures that were tried soon afterward usually had a low success rate because the patient’s body often rejected the new heart when leukocytes and other cells of the immune system recognized the new heart as foreign material and attacked it. With an improved understanding of immune system functioning and drug intervention, however, survival rates have gradually improved. Worldwide, approximately 3,500 patients undergo heart transplantation annually, with most occurring in the United States. The one-year survival rate is over 85 percent, the five-year survival rate is over 70 percent, the ten-year survival rate is over 50 percent, and some patients have lived longer than twenty years, according to statistics from the American Heart Association. In the United States, about fifteen thousand Americans aged fifty-five or younger (and forty thousand aged sixty-five or younger) would benefit from heart transplantation. Transplantation has been conducted with newborn babies, and adult patients have run marathons and even played professional sports. The average age at which the procedure is performed is forty-seven years for men and thirty-nine years for women.
The complications immediately following this type of surgery include irreversible damage to the heart, because of coronary atherosclerosis or multiple heart attacks, and primary or secondary cardiomyopathy, because the cardiac muscle cells cannot contract normally. Heart transplant recipients must take immunosuppressive (antirejection) medications for the remainder of their lives to prevent rejection; thus they must also cope with the numerous side effects of these drugs. For at least one year after transplantation, the heart is denervated (cut away from the body’s nervous system), causing a resting pulse rate of up to 130 beats per minute, as compared to 60 to 80 beats per minute in a normal heart. The chances for long-term success depend in part on the amount of damage or disease in other organs as a result of stroke, chronic obstructive lung disease, and liver or kidney disease. Transplant recipients must also deal with the psychological and emotional strain of the operation and its aftermath. Patients with a history of alcohol and drug abuse or mental illness, and those who lack a social support network of family and friends, are not considered good candidates for heart transplantation.
Perspective and Prospects
The rapid increase in the number of heart transplantations performed worldwide is attributable to specialized medical care and to numerous advances in knowledge regarding surgery, tissue preservation, immunology, and infectious disease. The extraordinary degree of success since the 1970s has enabled many patients who have undergone heart transplantation to live longer and more independent lives. Tremendous strides have been made in diagnosing rejection and developing immunosuppressive medications, and the development of several new antirejection drugs is anticipated soon. New techniques for diagnosing rejection candidates without the performance of a heart biopsy will be a major focus of future research, as will increasing access to donor organs. A better understanding of the immune system may give doctors greater success in transplanting organs from other species (a procedure called a xenograft) instead of human organs. Ongoing research will continue to focus on identifying risk factors for heart disease—such as high blood cholesterol and abnormal lipid subfractions, high blood pressure, diabetes mellitus, family history, and cigarette smoking—as early as possible in order to delay reaching the point at which heart transplantation is necessary.
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