Cellular response of the evolving myocardial infarction after therapeutic coronary artery reperfusion.

This study describes the cellular response of the evolving myocardial infarction in humans after early coronary artery reperfusion by one or more of the following therapies: streptokinase, percutaneous transluminal coronary angioplasty, tissue plasminogen activator, and/or coronary artery bypass graft surgery. Postmortem histologic changes were compared in two groups (n = 43 pairs) of human hearts with acute myocardial infarction matched for clinical age and left ventricular location of the infarct. The treatment group received one or more of the forms of reperfusion therapy. The control group received conventional therapy. The treatment group was judged to have an older histologic age infarct, P less than 0.002, compared with documented clinical age. For example, infarcts that were clinically 4 days old or less were judged histologically to be 1 day older. The treatment group had a higher Cellular Response Index, P less than 0.017; more hemorrhage within the infarct, P less than 0.001; a greater extent of selective myocardial cell necrosis, and a lesser extent of coagulation necrosis, P less than 0.05; more patchy, nontransmural distribution of necrosis, P less than 0.04; and a more florid cellular response, specifically more macrophages, P less than 0.034, and reactive stromal cells, P less than 0.05. In infarcts less than 3 days old clinically, the treatment group had hemorrhage and a cellular response which were wide-spread throughout the lesion, P less than 0.05, n = 18 pairs. In infarcts 3 to 4 days old clinically, the treatment group had a florid cellular response due to more macrophages, P less than 0.05, n = 9 pairs. In infarcts 5 to 10 days old, the treatment group had more macrophages, P less than 0.01; and more phagocytosis, P less than 0.003. In infarcts 10 to 40 days old clinically, the treatment group had scar formation that was patchy, P less than 0.05. In conclusion, this study demonstrates that early therapeutic coronary artery reperfusion after an acute myocardial infarction alters the pattern of injury and the cellular response to the evolving myocardial infarction so that the classical criteria for infarcts need to be modified.