Repeated myocardial infarction in non-arteriosclerotic and arteriosclerotic Sprague-Dawley rats.

Adult male Sprague--Dawley rats, with and without arteriosclerosis, were subjected to an isoprenaline-induced myocardial infarction. After 4 weeks' convalescence, the survivors were subjected to a second myocardial infarct. Animals free of arterial disease were able to survive only 2 infarcts, whereas those with preexisting arterial disease were able to endure a third and some a fourth infarct. Changes in serum enzymes (CPK, SGOT, SGPT and LDH), lipids (triglycerides, free fatty acids and cholesterol), glucose, BUN, and corticosterone manifested intensification or diminution of their characteristic response pattern with each subsequent episode of acute myocardial infarction and repair. Many animals died as a result of left ventricular aneurysm formation. Animals with pre-existent coronary artery disease were especially capable of affecting repair of the myocardium or aneurysmal wall through mesenchymal or fibroblastic activity.