Serial sectioning and multiple level examination of endomyocardial biopsies for the diagnosis of myocarditis.

To determine if serial sectioning and multiple level evaluation increase the sensitivity of endomyocardial biopsy for the detection of myocarditis, we prospectively studied all diagnostic endomyocardial biopsies between 1986 and 1989. Biopsies were embedded in paraffin, serially sectioned, and every 4-microns section was mounted in ribbons on glass slides. Every fifth slide was stained with hematoxylin and eosin and examined for myocarditis by the Dallas criteria (myocyte necrosis and inflammatory cells). Of a total of 153 biopsies, 20 cases (13%) were diagnostic of myocarditis on at least one section. Four biopsies (25%) were positive at slide Level 1, and 15 (75%) by slide Level 5; in five cases (25%), diagnostic foci were present only at or after slide Level 10. Multiple levels should be performed in the histologic evaluation of endomyocardial biopsies to increase the sensitivity of endomyocardial biopsy in the evaluation of myocarditis.