Cardiac rhythm and conduction disturbances: what is the role of autoimmune mechanisms?

The immunopathogenesis of cardiac rhythm and conduction disorders has been underestimated. Therefore, the aim of this review is to analyze the current data and controversial issues in this area. The incidence of autoantibodies to human conducting tissue has been analyzed in sick sinus syndrome, bradyarrhythmia, and hypersensitive carotid sinus syndrome. Patients with anti-sinus node antibodies (ASNab) have a 10-fold higher risk of developing sick sinus syndrome, compared to age-matched controls. The risk of acquiring an atrioventricular block was up to 3-fold in patients with anti-atrioventricular node antibodies (AAVNab) in comparison to controls. The incidence of anti His antibodies (AHISab) was low both in patients and controls. Anti-cardiac Purkinje cell antibodies (ACPCab) seemed to be an epiphenomenon and not a pathogenetic marker of conduction disorders. In congenital heart block association with HLA-B27 and HLA-DR3 is a possible prerequisite in the pathophysiology of the disease, although transplacental passage of various antibodies and immune complexes is widely recognized. The main autoantibodies detected both in children with congenital heart block and their mothers are anti-Ro/SS-A and anti-La/SS-B antibodies. The cross-reactivity of laminin with anti-La antibodies could be important in the initiation of the autoimmune process. Autoantibodies against adrenoceptors and muscarinic cholinergic receptors of neonatal heart and human endogenous retrovirus-3 expressed in fetal cardiac tissue could also play a role in the pathogenesis of the congenital heart block. Of note, apoptosis could be one of the possible mechanisms of the progression of the congenital conduction disturbances to the complete heart block. In addition, evidence is compiling that cellular activation and cellular cytotoxicity specific for a given target tissue appears to be at least equally important in the pathogenesis of the disease as the humoral response. In conclusion, the immunopathogenesis of certain cardiac rhythm and conduction disorders is well established in sick sinus syndrome, congenital heart block, and connective tissue diseases. ASNab, AAVNab, anti-Ro/SS-A, and anti-La/SS-B antibodies can be regarded as diagnostic and prognostic markers.