Effects of heparin in large doses on the extent of myocardial ischemia after acute coronary occlusion in the dog.

Heparin in large doses significantly improved epicardial electrocardiographic findings and preserved myocardial tissue and creatine phosphokinase (CPK) after coronary ligation in the dog. Epicardial S-T segment elevation 15 minutes after occlusion was lowered 84% (from 64.5 + 8.5 [standard error of the mean] to 10.4 +/- 3.0 mv) by heparin infusions of 60,000 units. Myocardial creatine phosphokinase depletion was reduced from 39 to 24% at comparable levels of S-T segment elevation. Histologic evidence of necrosis decreased 32%. It is concluded that heparin can reduce the extent of ischemic injury after acute coronary occlusion in the dog. These results may lend insight into the factors responsible for ischemic injury.