Antimyosin antibody imaging in clinical myocarditis and cardiomyopathy: principle and application

When cardiac myocytes fall into necrosis, their cell membrane integrity will be lost and myosin heavy chains inside the cells will be exposed to the circulation. Then, antimyosin antibody specifically binds to these exposed myosin molecules when they are injected into the patients. Myocardial imaging using indium-111 labeled antimyosin monoclonal antibody was performed in 26 patients. Forty-eight hours after the injection of radiolabeled antimyosin antibody, planer and single-photon emission computed-tomographic (SPECT) images were obtained. In myocarditis, all three patients at the acute stage showed positive scans, whereas six out of seven patients at the chronic stage showed negative, suggesting that antimyosin imaging may be used for evaluating whether myocarditis is active or healed. In dilated cardiomyopathy, seven out of 10 patients showed positive scans, and the ejection fraction of these patients was significantly lower than that of patients who showed negative. In hypertrophic cardiomyopathy, six out of seven patients showed positive scans. In particular, patients with dilated ventricle showed strongly positive, suggesting a correlation between antimyosin uptake and poor prognosis. Taken together, indium-111 antimyosin antibody imaging may be useful for evaluating diagnosis and prognosis of patients with myocarditis and cardiomyopathies.