Effect of reperfusion on myocardial infarct, and the accuracy of estimating infarct size from serum creatine phosphokinase in the dog

Abstract

This study was designed to determine the effect of coronary reperfusion on (1) myocardial infarct size and (2) the accuracy of previously reported methods for estimation of infarct size from serum creatine phosphokinase (CPK) values. Thirty mongrel dogs, chronically prepared, were studied in the awake state, and were divided into four groups according to the period of left circumflex coronary artery (LCCA) occlusion. Group 1: permanent occlusion (24 h) in nine dogs; group 2: 45 min occlusion (eight dogs); group 3: 1 h occlusion (five dogs); and group 4: 3 h occlusion (eight dogs). Serial blood samples were drawn for 24 h following the beginning of occlusion and were used to determine total and isoenzyme levels of CPK, and lactic dehydrogenase isoenzymes. All dogs were sacrificed 24 h after the beginning of occlusion and were anatomically examined. The extent of anatomical myocardial infarction was determined and compared with the extent of myocardial infarction as estimated from serial serum CPK values. Total serum CPK increased significantly in all groups and was associated with the appearance of CPK-MB isoenzyme and an increase in LDH_1.2 (LDH₁>LDH₂) in most dogs. Total serum CPK increased within an hour after reperfusion and the mean values in groups 2, 3, and 4 were significantly higher (P <0.05) than serum CPK values in group 1 in the period from 110 min to 4 h after occlusion. These data demonstrate that reperfusion after 45 min to 3 h of coronary occlusion results in an earlier appearance of total serum CPK. The anatomical infarction in group 1 averaged 28±3% (SEM) of the total heart and was significantly larger than infarct size in all groups with reperfusion. In contrast, estimated infarction calculated from total CPK in group 1 was not significantly different from the reperfused groups. Although there was correlation between estimated and anatomical infarction, the data in each group showed that anatomical infarct size could not be accurately estimated from total serum CPK.