Antimyosin monoclonal antibodies for early detection of cardiac allograft rejection.

Sixty-eight indium 111-labeled antimyosin Fab-DTPA imaging studies (0.5 mg intravenously with a radioactivity of 65 to 75 MBq) were executed on 37 of 116 patients undergoing heart transplantation to assess diagnostic accuracy and clinical utility. As controls, 21 patients with cardiomyopathy (n = 8), unstable angina (n = 9), and myocardial infarction (n = 4) were selected. After 48 hours, single photon emission computed tomographic images were evaluated visually, and heart/lung ratios were measured, using the "region of interest" technique. They were compared with echocardiographic and endomyocardial biopsy results. In 40 studies a heart/lung ratio less than or equal to 1.6 corresponded to a negative biopsy result in 98% (40/41). Echocardiography enabled correct identification of 95% of the patients with normal biopsy findings. In 91% (22/24) a positive biopsy finding correlated with a heart/lung ratio greater than 1.6 including 20 mild rejections, but in only 64%, with an increase in wall thickness and/or decrease of fractional diameter shortening seen on echocardiogram. In addition, the various stages of rejection episodes determined the amount of the heart-lung ratio. There was a significant relationship between the histologic findings and the antimyosin uptake. In 13 patients a second investigation was performed after rejection therapy. All patients had a negative biopsy result, and the heart/lung ratio decreased to normal ranges (less than or equal to 1.6). Five antimyosin antibody studies were excluded, as in these cases, negative uptake results were found during rejection therapy with high-dose steroids. The overall sensitivity was calculated at 93% and the specificity at 98%.(ABSTRACT TRUNCATED AT 250 WORDS)