Is immunoperoxidase staining of endomyocardial biopsies for interstitial inflammatory cells helpful in the diagnosis of myocarditis?

Abstract

Quantitative evaluation of interstitial inflammatory infiltrates has been proposed as a criterion to distinguish myocarditis from noninflammatory heart disease. Leucocytic infiltrates were quantitated by an immunoperoxidase technique on a single frozen fragment in 199 consecutive endomyocardial biopsies from 160 patients. Biopsies with a histological diagnosis of myocarditis showed a higher mean number of leucocytes per mm2 compared to biopsies diagnosed as normal, nonspecific or resolved myocarditis; however, the range of counts revealed considerable overlap with the other diagnostic categories. Therefore, myocarditis cannot be diagnosed based on interstitial inflammatory cell counts alone. However, quantitation of immunoperoxidase-stained leucocytes may prove useful in identifying patients with increased interstitial inflammation to determine the nature of ‘borderline’ myocarditis.