[Myocardial ultrastructure in experimental stenosis of the thoracic aorta in dogs]

Myocardium of the left ventricle of the heart has been studied in 15 dogs with an experimental aortic stenosis and in 5 control dogs. It has been demonstrated that 15-30 min after stenosis of the thoracic aorta, certain destructuve changes occur, first of all in myocitic mitochondria; later, myofibrillar and capillary endothelial cells lesions are revealed. The destructive changes are mostly pronounced 1-2 days after the aortic stenosis. Mosaic picture depending on heterogeneity of cardiomyocitic ultrastructure is observed. At the same time, certain compensatory changes take place: increase in number of ribosomes, polysomes, outgrowth of the granular sarcoplasmic reticulum, division and increase in size of mitochondria. Myofibrillar hypertrophy, noted 1 week after the operation, stabilizes by the 2nd month. Later (more than in a year), structural rearrangement of myofibrillae and increased mitochondrial destruction are noted.