An Electron Microscopic Study of Myocardial Ischemia in the Rat

Myocardial infarcts were produced in rats by ligating the anterior descending branch of the left coronary artery. After one hour, changes in the ultrastructure of myofibers in the infarcts were readily demonstrated by electron microscopy. These changes became progressively severe with time, and consisted primarily of swelling of mitochrondria and sarcoplasmic reticulum followed by increased lipid droplets and myolysis. Autolysis Atolysis of myocardium was also studied and the changes found to be similar to those of myocardial infarcts, but more uniform and slightly delayed in development. Perhaps the early ultrastructrural changes are related to hyperosmolarity of mitochondria and sarcoplasmic reticulum, especially after cell death. It is hoped that definition of ischemic ultrastructural change will be useful in defining electron microscopic lesions in other forms of myocardial damage.