[Interstitial microfibrils in the myocardium in rheumatic and congenital heart defects].

Electron-microscopic and electron-histochemical studies of biopsies of the myocardium from the patients suffering from rheumatic and congenital affections of the heart showed that hyperplasia of aperiodic argyrophilic and ruteniophilic microfibrillae served as the ultrastructural equivalent of coarsening of the reticular frame of the hypertrophic myocardium. Relapse of the rheumatic process is accompanied by irregulation and possibly by an increase in the number of microfibrillae due to their accelerated neoformation and defibrillation of the collagen fibrils with a periodicity of 640 A. There was traced no direct relationship between the amount of microfibrillar material on the surface of the muscle cells and the extent of destruction of their organellae; this, however, did not exclude the possible interrelation between the myocardial insufficiency and hyperplasia of the myofibrillae as an integral component of fibrosis and sclerosis of the myocardium.