Antibodies to cardiac conducting tissue in progressive systemic sclerosis.

Cardiac conducting tissue antibodies (CCTA) were detected, using indirect immunofluorescence, in 8 (25%) out of 32 sera from patients with progressive systemic sclerosis (PSS) and in 39 (35%) out of 110 with rheumatoid arthritis (RA). Conduction abnormalities, namely right bundle branch block, were present in 19 (59%) of the PSS patients and in 37 (32%) of the RA cases. No significant correlation was found between the prevalence of CCTA and conduction abnormalities in PSS patients, while this was present in RA patients (p less than 0.001). CCTA were always negative in 18 patients with systemic lupus erythematosus and were found in one out of 8 cases with Sjögren's syndrome, also positive for rheumatoid factor without clinical RA. These data suggest that CCTA are evoked when involvement of cardiac conducting tissue (as in RA) or working myocardium (as in PSS) is present. Whether CCTA should be mainly regarded as an expression of the immunological derangement underlying these pathological conditions or whether they are secondary to myocardial tissue damage, must still be clarified.