Heart Transplantation

Over the past decade heart transplantation ( HT ) has evolved from a rarely performed procedure to an accepted therapy for advanced heart failure. The need for HT as a therapeutic option is underscored by some important facts regarding heart failure. It is estimated that each year 40.000 patients with heart failure progress to end-stage disease. Drugs that improve heart failure outcome have decreased short and medium-term mortality by an average of only 20 %. The 3 to 4 year mortality and hospitalization rates remain 50 % even in patients treated with the best drugs available. Hence the need to offer heart failure patients nonpharmacologic measures.

After a sharp increase in the number of procedures during the mid 1980s, during the past 5 years the number has remained static and has not exceeded 3500 per year worldwide. The stunted growth of HT procedures is due to a critical donor shortage. Since 1987, when the United Network for Organ Sharing ( UNOS ) began operating, the supply of donor organs has not kept pace with demand, and the discrepancy between the number of donor organs available and the number of HT candidates continues to widen. In fact, the modest increase in the number of organ donors reported in recent years by UNOS is entirely attributable to the acceptance of increasingly older donors.

Indications and Recepient Selection

The most important task of heart failure specialists is to select the patients most likely to derive the greatest benefit from the procedure and, at the same time, who are at the highest risk of death without HT. To successfully acomplish the difficult task of candidate selection, it is critical to exclude the presence of reversible causes of heart failure in each and every patient referred for HT. In the absence of reversible causes, physicians must then weigh the relative risk of coexisting morbidities, keeping in mind that the risk of a poor outcome after HT increases continuously with each comorbid condition and may be additive. The next step is to predict the patients' prognosis based on clinical, functional, neurohormonal and arrhytmic variables. When doing so, some important guidelines should be followed . First, prognostic variables should be measured only after therapy has been optimized. Second, variables such as New York Heart Association functional class and left ventricular ejection fraction loose their discriminatory power in patients with advanced heart failure. Third, the prognosis of patients with advanced disease should be predicted as much as possible on the basis of objective criteria, such as peak exercise oxygen consumption ( VO2 max ) and determination of plasma norepinephrine levels. The measurement of VO2 max. has been a useful supplementary criterion not only for the selection of patients for HT but also for its timing. Maximal exercise performance exceding 14ml/kg/min predicted a 1 year survival of greater than 90 % ( which is higher than 1 year survival after HT, so that it can be safely postponed ). The worst outlook was for those patients whose peak VO2 was <>

If these variables predict a poor outcome despite optimal medical therapy, the next step in the process of selection is evaluation of the presence and reversibility of pulmonary arterial hypertension. This is an important consideration, since orthotopic HT requires that the pulmonary vascular resistance be low, so that the normal right ventricle of the donor heart can adequately support the recipient's circulation after transplantation.