HEART TRANSPLANTATION
Transplantation of the heart has been surgically feasible since 1960, when the essence of the surgical method was propounded. The important restrictions of the immune reaction and recipient selection remain, even though clinical experience was begun with the work of Barnard in South Africa and Kantrowitz in New York. Several early problems (e.g., surgical method) required solution before any animal could survive orthotopic homotransplantation of the heart. Another problem was protection of the donor heart against irreversible damage from its removal to reestablishment of coronary circulation. Also, the heart-transplantation physiologic process involved assessment of the effect of total cardiac denervation. Drugs such as digoxin had no effect on the A-V node; atropine had no chronotropic effect; nifedipine had no reflex tachycardia; and verapamil and beta blockers were still useful to treat supraventricular tachycardia.
The midline sternotomy provides
optimal exposure. Protection of the heart transplant is achieved by cooling
with physiologic saline solution at 2° to 4° C. Plate 6-141 illustrates the surgical method of biatrial transplantation, which
depends on retention in the host of parts of both atria and the interatrial
septum to which the transplant is sutured. Accordingly, after division of the aorta and pulmonary trunk immediately above
their respective semilunar valves, the atria are incised so as to leave intact
parts of the right and left atrial walls and the atrial septum of the
recipient. Because of the disproportion between the normal donor heart and the
larger recipient organ, the donor heart is removed by individual division of
each of the six inflow veins. Conceivably, in infants and children, the donor
heart may be of the same size as that of the recipient; if so, individual sectioning of donor inflow vessels
would not be necessary. Plate 6-142 illustrates the technique of bicaval
transplantation.
Resuscitation of the donor heart is
mandatory before proceeding with thoracotomy in the recipient. The explanted
donor heart is infused with cardioplegia and cooled. Ventricular fibrillation
of the donor heart routinely develops, and no attempt is made to convert this arrhythmia to an effective contraction.
Follow-up of Transplant Patient
After cardiac transplantation, the
patient requires follow-up by physicians expert in heart failure and
knowledgeable in immunology and infectious disease, with a focus on cardiac
function, cardiac rejection, anticipation of possible rejection, and treatment
of rejection and other aspects of immunosuppression, such as drug interaction.
In addition, recipients must recognize their responsibility to take care of the
transplanted heart. When all this is accomplished, the average survival of a
transplant recipient is 10 years. Late deaths are usually from transplant
coronary artery vasculopathy. A few patients live 20 years or more, possibly
related to their course, which had few episodes of rejection, infection, or
malignancy.
Moral, Ethical, and Social Implications
The several years’ delay for the
successful application of orthotopic homotransplantation of the heart in humans
was the result of the necessary experience with immune suppression in the
initiation of heart transplants as well as the long-term laboratory
observations determining whether absent CNS reflexes had prohibi- tively
deleterious effects on cardiac performance. Also
experimentally, a demand form of
immunosuppressi was formulated to cope
specifically with the heart trans- plants. Merely transposing accepted immune
chemotherapy from kidney transplants to heart transplants tended to
oversimplify the problem.
One of the most challenging and
difficult aspects of human heart homotransplantation is selection of the
recipient. Any patient whose heart has failed to the point where replacement is
indicated may have irreversible damage of other organ systems. Cardiac
transplantation, has little to offer the patient at risk for sudden cardiac death from any cause. Acute cardiac care
units have greatly reduced early mortality from ventricular fibrillation and
other arrhythmias secondary to acute myocardial infarction. Modern therapy of
heart failure and acute MI may have reduced the need for heart transplant, even
though severe heart failure from MI is still a prominent indication for
transplant.
Probably the most appropriate adult
candidate for heart transplantation is the patient with severe nonischemic
cardiomyopathy. These patients often present a
relatively long history of marginal
compensation, but with increasingly frequent episodes of decompensation. The
patient does not rally, unlike the typical patient with coronary artery
disease. In the last stages of nonischemic cardiomyopathy, heart
transplantation may be the only therapeutic application of choice. The
secondary effects of CAD, such as ventricular aneurysm, mitral valve
insufficiency, or ventricular septal defect, frequently are well treated by
conventional open-heart surgery, but no such program is available for the
patient in the terminal phases of nonischemic cardiomyopathy. The etiologic
factors in unrelenting heart failure are not well understood, but viral
infections may play a role.
Another important application of
heart transplantation is in the infant with a congenital cardiac anomaly for
whom there is no corrective operation or palliative procedure. Great difficulty
is encountered in this group of patients because of a paucity of donors and
technical surgical problems.
The successful transplantation of
the liver by Starzl and associates established the transplantation of unpaired
organs. The general public appeared ready for the concept that death of the
individual occurs stepwise, with the
brain dying first, then the heart, liver, and kidneys undergoing irreversible
damage. These organs clearly cannot be transplanted, and various methods are
necessary to resuscitate the heart in a prospective donor who had brain death.
Recipient selection may be more controversial than donor selection. Time and
practice has permitted the evolution of satisfactory criteria for transplant
recipients.
The advent of clinical heart
transplantation does not relegate the development of ventricular-assist devices (VADs) to total obscurity. At this time, VADs
are used as a bridge to transplant and in some patients as “destination
therapy” (see Plate
6-143). The future of heart
replacement has by no means been settled with the initial application of
homotransplantation. Future strides will consist of important research in the
area of rejection, including better monitoring, better immunosuppression, and
better organ preservation. If the issue of immune tolerance can be overcome,
cardiac transplant patients may live normal life spans.
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