Recipient Criteria and Preoperative Assessment

Patients undergoing heart transplantation must have end-stage cardiac disease with limited life expectancy. Management options other than transplantation should be fully explored. These include optimization of medical therapy; coronary artery bypass graft surgery for patients with suitable coronary anatomy and reversible ischemia on viability testing; mitral valve repair for patients with severe mitral regurgitation; insertion of an implantable defibrillator for those with recurrent arrhythmias; and biventricular pacing for patients with prolonged intraventricular conduction. In addition, because of the shortage of suitable donors, patients with end-stage heart failure may be offered a ventricular-assist device as “destination” therapy (see Chapter 22).

The two main pathologies that give rise to end-stage cardiac failure necessitating heart transplantation are ischemic cardiomyopathy and the nonischemic cardiomyopathies (dilated, hypertrophic, restrictive), which make up about 45% of cases each.⁵ The remaining cases include valvular heart disease, congenital heart disease, and primary heart transplant failure. Inclusion and exclusion criteria for recipients of heart transplantation are outlined in Table 14-1.⁶

Table 14-1 Recipient Selection Criteria for Heart Transplantation

* Mancini DM, Eisen H, Kussmaul W, et al: Value of peak exercise oxygen consumption for optimal timing of cardiac transplantation in ambulatory patients with heart failure. Circulation 83:778-786, 1991. NYHA, New York Heart Association; VO_{2 max}, maximal exercise.

The assessment of a patient’s suitability for heart transplantation includes a right heart catheter study (see Chapter 5). This is a critical investigation because the presence of elevated pulmonary vascular resistance (>5 Wood units) contraindicates heart transplantation. A resistance level above 3 Wood units indicates an increased risk for postoperative right ventricular dysfunction.

A potential recipient is tested for ABO blood group and for the presence of antibodies to human leukocyte antigens (HLA). The latter is referred to as panelreactive antibodies and is expressed as the percentage of volunteer donor blood to which the patient’s serum reacts. A potential recipient with a high percentage of panel-reactive antibodies is less likely to have a negative (i.e., acceptable) cross-match with a potential organ donor and is therefore likely to have to wait longer for a suitable heart. Such a patient is also more likely to develop rejection following transplantation (see Hyperacute Rejection in the subsequent material).

Patients undergoing heart transplantation in the United States are typically extremely unwell: 70% are hospitalized; 25% require some form of mechanical cardiac support (ventricular-assist device or intraaortic balloon pump); and almost half are undergoing intravenous inotropic infusions.⁵ For patients with decompensated heart failure who are receiving inotropic drugs, the insertion of a ventricular-assist device prior to transplantation (i.e., as a bridge to transplantation rather than as destination therapy) may improve outcome after surgery.⁷

Evaluation of potential heart transplant recipients should be undertaken by a multidisciplinary team that is experienced in the management of severe heart failure and transplantation. This team includes cardiologists, cardiac surgeons, transplant coordinators, psychologists, social workers, dieticians, physiotherapists and, for critically ill patients, intensivists.

Donor Criteria and Management

As well as recipient criteria, donor criteria are vital in the decision to proceed with transplantation. An important criterion is the absence or low probability of coronary artery disease in the donor heart. For this reason, the upper donor age limit in most transplant units is 55 to 60 years.⁸ An echocardiogram is performed to assess valvular and ventricular function. The presence of segmental wall motion abnormalities is suggestive of myocardial ischemia or infarction and precludes the use of the organ. In some centers, coronary angiography is performed in potential donors who have risk factors for coronary artery disease.

The requirement for high-dose inotropic support in a donor is a relative contraindication to use of the heart for transplantation, particularly if it is associated with echocardiographic evidence of impaired ventricular function. The neuroendocrine failure that accompanies brain death is associated with marked vasodilation (see Chapter 38), and it usual for there to be some requirement for a vasopressor. The effects of neuroendocrine failure may be ameliorated by employing hormonal therapy (vasopressin, cortisol, triiodothyronine, insulin-glucose) in the donor. This regime may increase the number and quality of organs available for use in heart transplantation.

Ideally, the donor heart’s ischemic time should be less than 6 hours. In one study, an ischemic time greater than 4 hours was associated with increased rates of early mortality.⁹ In an attempt to extend the safe ischemic time, continuous perfusion systems (as opposed to standard cold storage) have been developed. These systems are complicated and have not been widely adopted.

Recipient-Donor Matching

The matching of recipients and donor organs within a particular country (or group of countries) is typically under the control of a single allocation agency; in the United States, it is the United Network of Organ Sharing (UNOS). Based on UNOS criteria, thoracic organs are offered on the basis of geography, donor-recipient compatibility, and medical urgency: