DILATED CARDIOMYOPATHY - A CHRONIC MYOCAR DITIS - NEW ASPECTS IN DIAGNOSIS AND THERAPY

Clinical and experimental data suggest that autoimmunological mechanis ms may play an important role in the pathogenesis of postmyocarditic c ardiomyopathy This may be due to the viral infection itself, or may be induced by persistence of the virus. Apart from the clinical signs of myocarditis, which are usually not specific, the diagnosis of acute m yocarditis should be enabled by the histological examination of endomy ocardial biopsies. In accordance with the Dallas criteria the histolog ical diagnosis of acute myocarditis is defined by the presence of infl ammatory cells in the myocardium associated with myocyte necrosis and degeneration of adjacent myocytes. This morphology, however, is only s een within the first 7 to 10 days of the acute stage of the disease. L ater, most cases of clinically suspected acute myocarditis are histopa thologically consistent with the diagnosis of ''borderline myocarditis ''. Although endomyocardial biopsies have markedly improved diagnostic possibilities, the diagnosis of myocarditis by light microscopy has i ts limitations. Mainly the differentiation of infiltrating mononuclear cells from interstitial fibroblasts or pericytes is visually difficul t. New immunohistochemical methods were therefore introduced to improv e the specificity and sensitivity of the diagnosis. Using monoclonal a ntibodies against cell surface markers from lymphocytes (CD3, CD4, CD8 ) the identification, characterization and quantification of lymphocyt ic infiltrates in the myocardium is improved very significantly Furthe rmore, the use of monoclonal antibodies against MHC-class-I and class- II-antigens provides further information about the immunological statu s of the myocardium. In conclusion, the use of these new immunohistolo gical methods offers the possibility of establishing immunological cri teria in addition to histological parameters, This, permits a more acc urate diagnosis and a better understanding of immune mechanisms possib ly involved in the pathogenesis of chronic myocarditis and/or dilated car diomyopathy. Recent data using immunohistochemical methods have sh own that about 35 %-40 % of patients with clinically suspected dilated cardiomyopathy have lymphocytic infiltrates and an increased MHC-clas s-I and class-11-antigen expression in the myocardium. On the assumpti on that this can be taken as an indication for an active autoimmunolog ical process, these patients were treated in an open non-randomized pr ospective trial with prednisolone. 23 out of 31 patients showed a sign ificant improvement of their clinical, hemodynamic and immunohistochem ical status. These data indicate that the histological and immunohisto chemical evaluation of myocardial biopsies might help to identify pati ents with clinically suspected dilated cardiomyopathy who have a chron ic myocarditis and can possibly be improved by immunosuppressive thera py. However, a definitive assessment of the usefulness of immunosuppre ssive therapy in chronic myocarditis is not possible until double-blin ded randomized studies have confirmed these results.