The only reliable means of diagnosing acute cardiac rejection before substantial myocardial damage has occurred is

Of the major complications, allograft rejection is the primary problem requiring surveillance; scheduled endomyocardial biopsy is the only reliable means of diagnosing acute cardiac rejection before substantial myocardial damage has occurred and at a stage that is reversible in the majority of instances. Rejection is characterized by interstitial lymphocytic inflammation that, in its more advanced stages, damages adjacent myocytes; the histology resembles myocarditis. When myocardial injury is not extensive, the “rejection episode” is usually either self-limited or successfully reversed by increased immunosuppressive therapy. Advanced rejection may be irreversible and fatal if it is not promptly treated.