Exercise-induced complete heart block in a patient with chronic bifascicular block.

Heart block induced by exercise or associated with symptomatic, chronic bifascicular block can progress to high-grade atrioventricular (AV) block and sudden death. The authors describe a case of exercise-induced AV block in a patient with chronic bifascicular block. Thirty seconds of ventricular asystole were observed during exercise treadmill testing. Myocardial ischemia was ruled out, and the cause was determined to be distal AV nodal block. The pathophysiology, diagnosis, and treatment of distal AV nodal block are reviewed. The role of exercise treadmill testing and electrophysiologic studies in distal AV block are outlined in a diagnostic and therapeutic strategy.