Exercise-induced Atrioventricular Block Progressing to Complete Atrioventricular Block 4 Years after the Initial Presentation: A Case Report.

A 66-year-old man presented with dyspnea which occurred while running for 3 months. His resting electrocardiogram was normal, but a treadmill test revealed a 2:1 atrioventricular (AV) block when the sinus rate increased to 142 beats per minute. We diagnosed exercise-induced AV block and implanted a dual-chamber pacemaker. Initially, the ventricles were paced mainly during exercise. However, the patient became dependent on ventricular pacing at rest 4 years after the initial presentation, and progression to complete AV block was thereafter confirmed. This case highlights that exercise-induced AV block is not a benign condition, and AV conduction can deteriorate further over time.