Indium-111 antimyosin scintigraphy to assess myocardial damage in patients with suspected myocarditis and cardiac rejection.

Indium-111 antimyosin scans were used to assess myocardial damage in patients with suspected myocarditis and cardiac transplant rejection. The calculation of a myocardium to lung ratio (AM index) to quantify antimyosin uptake was performed. AM index in normal subjects (n = 8) at 48 hr postinjection was 1.46 +/- 0.04. In patients with suspected myocarditis (16 studies in 13 patients), AM index was 2.0 +/- 0.5 (p less than 0.001); suggesting a considerable incidence of ongoing cell damage in this group, despite the small proportion of positive right ventricular endomyocardial biopsy (RVbx) (4/13). In patients studied after cardiac transplantation (37 studies in 17 patients), AM indexes correlated with RVbx. In patients with RVbx proven rejection (n = 14), AM index was 1.87 +/- 0.19 (p less than 0.001). In patients with RVbx showing infiltrates but not myocyte damage (n = 13), AM index was 1.80 +/- 0.27 (p = 0.02). In patients with normal RVbx (n = 10), AM index was 1.56 +/- 0.17 (p = NS versus controls; p = 0.001 versus those with positive RVbx). Calculated AM indexes correlated with graded visual analysis of the scans (r = 0.823; p = 0.001). Antimyosin scans are an appropriate method to assess myocardial damage in patients with suspected myocarditis and cardiac rejection.