Diagnosis of acute cardiac rejection with antimyosin monoclonal antibody, phosphorous nuclear magnetic resonance imaging, two-dimensional echocardiography, and endocardial biopsy.

A cervical heterotopic cardiac allograft model was used to compare noninvasive techniques with endocardial biopsy diagnosis of rejection. The transplant procedure was performed in eight dogs (12 to 16 kg), with a mean ischemic time of 83 minutes. Beginning on the day of the operation each allograft was evaluated daily by palpation, two-dimensional echocardiography, phosphorous nuclear magnetic resonance spectroscopy, and septal endocardial biopsy. At specific intervals after the operation, antimyosin monoclonal antibody (Fab fragment) with an indium-111 label was administered for subsequent gamma camera imaging. Rejection was clinically evident by 2 to 8 days with a mean of 3.5 days. Endocardial biopsy demonstrated moderate to severe rejection by 2 to 4 days. Two-dimensional echocardiography demonstrated early loss of wall thickening dynamics in all allografts. Although subtle changes were evident early in some transplants, these findings were not consistent. After recovery from hypothermic ischemia, evaluation of high energy phosphate metabolites with phosphorous nuclear magnetic resonance spectroscopy showed a progressive decrease in phosphocreatine during mild to moderate rejection, dropping to 30% to 40% of baseline levels with severe rejection. Antimyosin antibody uptake directly correlated with endocardial biopsy rejection scores (R2 = 0.97). With mild to moderate rejection, mean total counts and corrected counts were 222,704 and 112,648, respectively, and were significantly different (p less than 0.05) from baseline counts (135,537 and 58,530) without rejection. As a preliminary finding in untreated acute rejection, both antimyosin antibody and phosphorous nuclear magnetic spectroscopy detected changes consistent with mild to moderate rejection, which usually preceded echocardiographic evidence for injury.(ABSTRACT TRUNCATED AT 250 WORDS)