Scar formation in the cardiac conduction system of a patient with Takayasu's arteritis.

An autopsied case of Takayasu's arteritis associated with complete atrioventricular (AV) block is described for the first time. The findings of scar formation and diffuse infiltration of lymphocytes into the cardiac conduction system, particularly the AV node, were similar to those in patients with connective tissue diseases or congenital complete heart block. The degree of AV block progressed with aggravation of the disease. These findings suggest that complete AV block may have been induced by acquired autoimmunity involving the cardiac conduction system.