Indium-111 monoclonal antimyosin cardiac scintigraphy in suspected acute myocarditis: evolution and diagnostic impact.

BACKGROUND: This study examined the evolution of the heart to lung (H/L) ratio of monoclonal antimyosin antibody (MAA) uptake in patients with suspected acute myocarditis (AM) and its time-dependent diagnostic value in conjunction with echocardiographic findings.

METHODS: The study included 20 patients with a short history (<4 months) of heart failure symptoms and normal coronary arteries. All patients underwent cardiac antimyosin scintigraphy, echocardiography, right-heart catheterization and endomyocardial biopsy. Patients who survived beyond 1 year were reevaluated with a cardiac antimyosin scintigraphy and an echocardiographic study.

RESULTS: Endomyocardial biopsy in 8/20 patients revealed findings compatible with the diagnosis of idiopathic dilated cardiomyopathy (group I) and in the remaining 12/20 was diagnostic of AM (group II). At baseline evaluation of the antimyosin H/L ratio uptake was similar in groups I and II, at 1.95+/-0.19 and 2.16+/-0.51, respectively (P=0.222), while the left ventricular end diastolic diameter (LVEDd) was significantly higher in group I (68+/-12 mm) than in group II (56+/-11 mm, P=0.041). In these patients an initial positive MAA scintigraphy (H/L ratio>1.55) associated with an LVEDd
CONCLUSIONS: In patients with suspected AM a positive antimyosin scintigraphy accompanied by a non-dilated left ventricle is highly suggestive of AM, both at the early phase and 1 year after disease onset.