Graft rejection remains a major factor limiting long-term survival despite continued advancement in the use of immunosuppression. Aggressive surveillance using the gold standard of endomyocardial biopsy (EMB) for the detection of acute rejection is therefore necessary. Repeated EMB (a minimum of 11 times the first year after heart transplantation) remains the only reliable surveillance method available. EMB is expensive, invasive, inconvenient to the patient, and associated with a significant incidence of serious complications.