Myocardial uptake of antimyosin antibody in idiopathic dilated cardiomyopathy and its relation to functional and morphological parameters.

Monoclonal 111In antimyosin (AMS) uptake indicates the presence of ongoing myocyte damage. In idiopathic dilated cardiomyopathy (IDC), there is diffuse myocyte damage. We have attempted to find a correlation between AMS uptake and functional myocardial parameters. With this purpose in mind, we studied two groups of subjects: group 1 comprised 19 subjects with IDC and group 2 comprised 6 control subjects. In all subjects, an antimyosin scan was performed. Among the subjects with IDC, two-dimensional echocardiography was carried out to determine the left ventricular ejection fraction (LVEF) and left ventricular dimensions, and a gated blood pool study was undertaken to assess the LVEF at rest and end-diastolic and end-systolic volumes. Three months later, repeat antimyosin scintigraphy and equilibrium gated blood pool were performed on 13 of the patients. The mean heart to lung (H/L) ratio in the IDC subjects was 1.82 +/- 0.25 (range 1.42-2.25), a value significantly higher than that obtained in the controls: 1.41 +/- 0.12 (range 1.26-1.58) (P < 0.001). Linear regression analysis did not find a statistically significant correlation between H/L and gated blood pool or echocardiography measures. No marked changes in ejection fraction and antimyosin uptake were found between baseline and follow-up studies. Subjects with IDC have a high incidence of positive antimyosin scans, but antimyosin uptake is not related to any functional or morphological parameters.