In adults the most common cause of acquired complete heart block is:

B. Sclerodegenerative disease.

DISCUSSION: Before permanent pacemakers were available, 50% of patients with complete heart block died within 1 year. The most common cause of acquired complete heart block in adults is sclerodegenerative disease of the cardiac skeleton and AV conduction system. Other less common causes of complete heart block include ischemic heart disease, cardiomyopathic processes, Chagas' disease, and traumatic injury.