Evaluation of the membrane attack complex of complement for the detection of a recent myocardial infarction in man

The diagnosis of an acute myocardial infarction (MI) can be cumbersome for pathologists. Even with a positive nitroblue tetrazolium (NBT) reaction, ha ematoxylin and eosin (H&E) evaluation of the myocardial tissue can remain i nconclusive. Early signs presumed diagnostic for myocardial infarction, suc h as hypereosinophilia, waviness, and contraction band necrosis, have to be considered non-specific and are probably reversible signs of ischaemia, Se veral studies implicate the complement system, and especially complement fa ctor C9, as part of the membrane attack factor (MAC), in cardiomyocyte dama ge during MI. In a post-mortem study on well-documented cardiological autop sies, we evaluated the use of complement factor C9 immunostaining as a mark er for the detection of very recent MI. Forty-three tissue samples from 40 patients were obtained from the left ventricular free wall only, a region t hat can be specifically attributed to one corresponding coronary artery, As some patients presented with MIs of various stages in that perfusion area, in total 57 observations were possible. C9 immunostaining specifically det ected irreversibly damaged (= infarcted) cardiomyocytes, as is implied by t he lytic activity of C9/MAC binding to cell membranes. Most interesting was the group of clinically suspected, NBT-positive Mis resulting from very re cent myocardial ischaemia. In this population, where H&E evaluation by (car dio-) experienced pathologists was not conclusive, C9 immunostaining clearl y pointed towards myocardial infarction in 47% of the cases. In conclusion, C9 immunostaining, routinely practicable in the pathology laboratory, has an additional value in discriminating between reversible ischaemia and infa rcted cardiomyocytes in very early MIs. Copyright (C) 2000 John Wiley & Son s, Ltd.