Anti-β-Adrenoceptors Autoimmunity Causing `Idiopathic' Arrhythmias and Cardiomyopathy

Background: To determine the prevalence of anti-β-adrenoceptors autoantibodies (aβAA) in patients with idiopathic arrhythmias (IA) and to assess whether aβAA are predictive markers for concealed cardiomyopathy in such patients. Methods and Results: Sixty-seven patients (group 1) with IA [25 supraventricular (SVA) and 42 ventricular (VA)]; 14 patients (group 2) with suspected cardiomyopathy, 12 patients with definite cardiomyopathy (group 3); and 19 healthy controls (group 4) were tested with an enzyme immunoassay, using synthetic peptides corresponding to the second extracellular loop of the human β1-and β2-adrenoceptors. Endomyocardial biopsy was performed in 29 patients. As compared with group 4 [3/19 (15.7%)], anti-β1-adrenoceptor autoantibodies (aβ1AA) were more frequent in group-1 patients [38/67 (56.7%; P