[Electron-microscopic study of the left heart ventricle of rats in the advanced stage of myocardial hypertrophy].

The ultrastructure of the left ventricle was studied in 10 rats, 5 of whom were subjected to partial ligation of the aortic isthmus 9 months prior to the procurement of the material. In 3 of the operated rats cardiac insufficiency was induced by means of additional exercises. Three normal rats could swim for 5 hours running before they got exhausted, 2 rats were intact. The operated animals with signs of cardiac insufficiency exhibited highly distinct ultrastructural changes that did not differ qualitatively from those observed in the acute phase of myocardial hypertrophy. No alterations were noted in the mitochondria, which does not permit to interpret the disorders in the energy balance of the cell as the leading cause of chronic cardiac insufficiency. In chronic cardiac insufficiency the myocardial cells seem to develop physiological disturbances undetectable by electron microscopy that may be the cause of cardiac failure. This is supported by the appearance of gross changes in the myocardium on the advanced stages of hypertrophy even after insignificant additional exercises.