Ultrastructural and immunohistochemical analysis of biopsy-proven chronic active mycocarditis with numerous clusters of lymphocytes.

A 60-year-old women was admitted to our hospital with deteriorating congestive heart failure. Although the diagnosis of active myocarditis was confirmed by right ventricular endomyocardial biopsy, this patient died of refractory heart failure during corticosteroid treatment. Numerous lymphocytic clusters were observed microscopically in the heart at autopsy. Most of the infiltrating cells in the clusters were positive for CD 8, HAM 56 or MHC class 2 antigen; few cells were positive for CD 56. Expression of perforin was found in some of the infiltrating cells. Electron microscopic examination revealed small lymphocytes adhering to the surface of injured cardiac myocytes. Close contact of these lymphocytes to macrophages was shown in the clusters. ICAM-1 and MHC class 1 antigens were strongly expressed in the cardiac tissue. These results indicate that cytotoxic T lymphocyte-mediated cytotoxicity had continued to operate during immunosuppressive therapy. Corticosteroids may not be suitable for the treatment of chronic active myocarditis when persistent expression of ICAM-1 is observed.