Identification of cardiac rejection in heterotopic heart transplantation using 111In-antimyosin.

It is important in heart transplantation to evaluate precisely the extent and location of cardiac rejection. At present, right ventricular endomyocardial biopsy has been used as the gold standard, however, establishment of noninvasive, simple, and easy diagnostic procedure is desired. The canine donor heart, in which atrial septal defect and tricuspid regurgitation had been produced beforehand, was heterotopically transplanted into the recipient's chest cavity. In seven dogs, two to three mCi of 111In-antimyosin was injected intravenously upon cardiac rejection before the heart was excised. 111In-antimyosin myocardial imaging was then performed using a gamma camera. In the same slice, a histopathological rejection score was calculated and divided into mild, moderate or severe injection. The uptake of 111In-antimyosin was significantly higher in moderate and severe rejected myocardium, since this agent produced a specific and selective localization and concentration in areas of myocardial damage. Therefore, this new technique allows the evaluation of therapeutic intervention upon cardiac rejection and may replace right ventricular endomyocardial biopsy.