Immune reactions in infective endocarditis. I. Clinical data and diagnostic relevance of antimyocardial antibodies.

Clinical data from 72 patients with infective endocarditis (41 with defined pathogen, 31 with no pathogen isolated) were analyzed with respect to the diagnostic relevance of immunologic parameters. In our patients from a rural area, no significant changes in the epidemiology and pathogenesis of infective endocarditis were observed. Antiendocardial and antisarcolemmal (ASA) antibodies were demonstrated in 60% to 100% of cases. Their frequency depended on the endocarditic pathogen and on the clinical course: in subacute or chronic endocarditis these antibodies were found regularly, in acute lethal cases their occurrence was diminished. Whereas antiendocardial antibodies are diagnostic markers of endocarditis, ASA and antimyolemmal antibodies in particular most likely indicate myocardial involvement in endocarditis. Only complement fixing antimyolemmal antibodies induced cytolysis of vital, adult, heterologous cardiac cells. Our data suggest that antibody-mediated cytolysis in vitro may also play a pathogenetic role in vivo.