The role of endomyocardial biopsy in the diagnosis of cardiac disorders in infants and children.

Endomyocardial biopsies from 26 children were studied by light and electron microscopy. Follow-up biopsies were obtained in 2 patients. The biopsy showed evidence of myocarditis in 6 patients, including 1 with features of sarcoidosis. Twelve biopsies showed features consistent with dilated cardiomyopathy. Endocardial fibroelastosis was documented in two of these biopsies. In two biopsies striking myocardial hypertrophy with prominent myofibrillar disarray suggested hypertrophic cardiomyopathy. Two biopsies from patients with clinical hypertrophic cardiomyopathy showed ultrastructural evidence of a mitochondrial abnormality. No morphological changes were detected in five biopsies, of which two had carnitine deficiency. A biopsy sampled the overlying myocardium in 1 patient with a cardiac fibroma, and a biopsy of the right ventricle was normal in a patient with Noonan's syndrome and hypertrophic cardiomyopathy limited to the left ventricle. Thus, of 28 biopsies in this series, the morphological changes were diagnostic in 10 (35%) and an additional 13 (46%) biopsies documented an abnormality of the myocardium. Endomyocardial biopsies can be of significant use in the diagnosis of selected cardiac disorders in childhood.