Ambiguity of morphological criteria of myocarditis in cardiac biopsy specimens

Abstract

Myocarditis is diagnosed when leukocytic infiltrate is accompanied by myocyte degeneration or necrosis. Endomyocardial biopsy is evaluated as the main diagnostic method. The purpose of the present study was to examine the individual elements of a histological picture and specify morphological criteria of diagnosing myocarditis in cardiac biopsy. The Dallas criteria were the point of reference. In the cardiobiopsies from 70 patients with clinically suspected myocarditis or congestive cardiomyopathy an active myocarditis was found in 19 cases, significantly more frequently in the group clinically classified as having myocarditis. Contraction bands, endocardial changes and vasculopathy were more frequent in cases histologically classified as active myocarditis than in borderline myocarditis. In our opinion the Dallas criteria include certain ambiguities concerning mainly differences of individual types and phases of myocarditis as well as their relations to congestive cardiomyopathy. The sensitivity and specificity of the diagnosis are related both to methodological limitations (material selection) and difficulties occurring mainly at the level of perception, evaluation and interpretation of changes. It is possible to improve the efficacy of cardiac biopsy in diagnosing myocarditis if a new techniques better revealing myocyte damage and more unequivocally determining the cellular composition of the stroma have been developed.