Field emission scanning electron microscopic study on the noninfarcted myocardium after myocardial infarction.

Intracellular membranous ultrastructural changes in the noninfarcted myocardium of the left ventricle were studied by examining experimental myocardial infarction in rats with a field emission scanning electron microscope. The left coronary artery was ligated at its origin for 7 days. The resulting infarcts comprised approximately 40% of the total area of the left ventricles. In a light microscopic study, the transverse diameter of myocytes had increased to 17.1 +/- 2.9 microns in the noninfarcted myocardium, compared to 14.1 +/- 3.1 microns in the myocardium of sham-operated rats (p less than 0.01). For the scanning electron microscopic study, the specimens were processed according to the Osmium-DMSO-Osmium method. Marked morphological changes of intracellular membranous structures were found in the noninfarcted myocardium, especially in the lacelike network of sarcoplasmic reticulum which occasionally formed large flattened cisternae, and in the marked proliferation of surface caveolae. It is speculated that these early ultrastructural changes in the noninfarcted myocardium reflect an adaptation of microorganellae in the failing hearts of the rats.