Quantitation of leukocytes in endomyocardial tissue from 100 normal human hearts at autopsy. Implications for diagnosis of myocarditis from biopsy specimens of living patients.

From 100 normal human hearts, evenly distributed by age and sex, 5 endomyocardial samples were obtained from the septal surface of each ventricle with a cardiac bioptome. In each case, from both ventricles, the number of lymphocytes, eosinophils, plasma cells, and neutrophils was counted in 10 high-power (x400) microscopic fields, and the mean number of each type of leukocyte was calculated. In 95% of the 2,000 high-power fields, the number of interstitial lymphocytes was less than 5.0. Moreover, in all but one heart, the mean number of lymphocytes was less than 4.0. The mean number of eosinophils was 0.0-0.1 and of plasma cells was 0.0-0.3. The median number of neutrophils was 0.6. Recognition of the normal number of leukocytes in the heart may help to minimize false positive interpretations of myocarditis in biopsy specimens of endomyocardial tissue from living patients.