Abstract
To evaluate the concordance between elevated plasma MB CPK and irreversible myocardial ischemic injury, coronary occlusion was induced for 10 minutes to 48 hours in 21 open chest dogs and 13 conscious animals. Results of plasma CPK and MB CPK assayed in samples obtained serially for 24 hours were compared to microscopic changes in hearts from the same animals examined 48 hours after occlusion. Twelve of the 34 dogs died within two hours after coronary occlusion. Among the surviving 22 dogs, one failed to exhibit gross or electrocardiographic evidence of ischemia and was therefore excluded. Twelve had coronary occlusion maintained for 30 minutes or longer and in 11 of these peak plasma MB CPK activity exceeded the normal range (mean ±2 SD) and baseline values by at least 100%. Necrosis was present in the hearts from each manifested by nuclear pyknosis, eosinophilia, shrinkage of cytoplasm, and leukocytic infiltration. In the remaining nine dogs with occlusion for less than 30 minutes, peak plasma MB CPK activity was not elevated and necrosis was not detected. The close concordance between plasma MB CPK elevations and myocardial necrosis was significant (chi2=14.5, P<0.001), and thus, increased plasma MB CPK activity reflected irreversible myocardial ischemic injury.