Histopathological assessment of endomyocardial biopsy in children: I. Semiquantitative study on the hypertrophy of cardiac myocytes.

Over 200 endomyocardial biopsies in pediatric patients have been performed since 1962, and an appropriate interpretation of myocardial hypertrophy in biopsy specimens at different ages is now necessary. The diameter of myocytes was measured in 108 biopsy specimens and 209 autopsy specimens from pediatric cases. There was a gradual increase in the myocyte diameter according to age in the biopsy and autopsy specimens. The diameter became adult size at 13 to 15 years of age in the right ventricle and at 9 to 15 years in the left ventricle. The myocyte size of diseased hearts was greater than that of normal hearts at each age. The coefficient of variance of the mean myocyte diameter in heart muscle disease, including hypertrophic cardiomyopathy and dilated cardiomyopathy, was greater than in other hearts. These results suggested that it is possible to ascertain myocardial hypertrophy by measuring the diameter of cardiac myocytes. A proposed grading system of the degree of myocyte hypertrophy for the biopsy specimens at various pediatric ages is reported.