To determine whether organ-specific cardiac autoantibodies are present in dilated cardiomyopathy, indirect immunofluorescence on human heart and skeletal muscle was used to test sera from 200 normal subjects and from 65 patients with dilated cardiomyopathy, 41 with chronic heart failure due to myocardial infarction and 208 with other cardiac disease. Three immunofiuorescence patterns were observed: diffuse cytoplasmic on cardiac tissue only (organ-specific), fine striational on cardiac and, to a lesser extent, skeletal muscle (cross-reactive 1) and broad striational on both cardiac and skeletal muscle (cross-reactive 2). Cardiac specificity of the cytoplasmic pattern was confirmed by absorption studies with homogenates of human atrium, skeletal made and rat liver.
Organ-specific cardiac antibodies (IgG; titer range 1/10 to 1/180) were more frequent in patients with dilated cardiomyopathy (17 [26%] of 65) than in those with other cardiac disease (2 [1%] of 208, p < 0.0001) or heart failure (0 [0%] of 41, p < 0.001) or in normal subjects (7 [3.5%] of 200, p < 0.0001). Organ-specific cardiac antibodies were more common in patients with dilated cardiomyopathy and in those with fewer symptoms (8 of 15 in New York Heart Association functional class I versus 9 of 50 in classes II to IV, p < 0.01) and more recent (<2 years) onset of disease (9 of 19 versus 8 of 46, p < 0.02). Conversely, cross-reactive antibodies 1 and 2 were detected in a similar proportion of patients with dilated cardiomyopathy (7 [11 %] of 65), other cardiac disease (15 [7%] of 208) or heart failure (1 [2%] of 41) and normal subjects (11 [5.5%] of 200, p = NS). The presence of organ-specific cardiac antibodies provides a novel serologic marker of cardiac autoimmunity in dilated cardiomyopathy.
