Idiopathic myocarditis characterized by marked right ventricular dilatation. Report of two autopsy cases.

We encountered two children with chronic idiopathic myocarditis accompanied by marked right ventricular dilatation, who died of progressive right heart failure. A definitive diagnosis was made by histological examination of the myocardium at autopsy. The patients were both boys, aged 7 years and 1 year and 4 months, and a number of identical features were evident upon physical and laboratory examinations. No heart murmur was heard, and gallop rhythm was noted in distant heart sounds. Electrocardiogram revealed intraventricular block, low voltage QRS complex, and ST-T abnormality. Two-dimensional Doppler echocardiogram and right ventriculogram showed marked dilatation and decreased contractility of the right ventricle as well as tricuspid regurgitation. Thinning of the wall and marked dilatation of the right ventricle were confirmed at autopsy. Our observations showed that chronic myocarditis associated with tricuspid regurgitation may readily lead to marked right ventricular dilatation even exceeding the degree of left ventricular dilatation. Idiopathic myocarditis associated with such unusual features is relatively rare, and may present problems in differentiation from other congenital heart diseases causing dilatation and dysfunction of the right ventricle.