Long survival with giant cell myocarditis

Several aspects of giant cell myocarditis remain controversial, including the natural history of the disease and the nature of the giant cells. We have observed three patients who had long survival with chronic active giant cell myocarditis. The first patient was a 59-yr-old female who had a 10-yr history of complete heart block which was found at autopsy to have been caused by giant cell myocarditis. The second patient is a 36-yr-old female who received a heart transplant 5 yr after a biopsy proven episode of active myocarditis, and examination of the explanted heart revealed giant cell myocarditis. The third patient was a 41-yr-old male who received a heart transplant 2 yr after developing progressive heart failure, and the explanted heart had giant cell myocarditis. On immunohistochemical study of the three hearts, the giant cells stained with the macrophage markers lysozyme and KP-1 (CD-68). Staining of the same cells with desmin and actin was focally positive in a punctate pattern, correlating with the ultrastructural presence of myofibrils within giant cell phagolysosomes. The associated lymphocytic infiltrate stained primarily for the T-cell markers CD-3, CD-45RO, and CD-43 whereas only a few of the lymphocytes stained with the B-cell marker CD-20. The long histories of cardiac dysfunction in the three patients show that giant cell myocarditis may have a protracted course. The morphologic studies show that the giant cells are of histiocytic origin but can contain phagocytosed components of myocytes, observations that may account for the controversy surrounding the nature of the giant cells in giant cell myocarditis.