This paper describes morphological and cytochemistry changes of endomyocardial biopsy in 94 patients. The samples of myoicardium were taken from 32 patients with dilated cardiomyopathy, and sdudied with light and electron microscop. The cytochemical studies in some of these patients were performed at histological and ultrastructure level. This paper also reported the result of myocardial biopsy in 33 patients with serious dysrythmia.The result of this controlled study indicates that morphological assessment in both cardiomyopathy and congenital or rheumatic heart diseases showed no special changes. In patients of dilated cardiomyopathy, the decreased activity of myosin ATPase was secondary to cardial failure. The change of succinate dehydrogenase (SDHase) was not significant with light microscopy. But ultrastructural localization of SDHase activity is valuable. Its activity was found to be localized in endomembrane and ridge of the mitochondria, the activity of this enzyme was decrease, normal, or increase. SDHase activity was more intense in cardial myocytes well-functioning, or ultrastructurally well preserved hearts.
