Trifascicular block progressing to complete AV block on exercise: a rare presentation demonstrating the usefulness of exercise testing.

A 41-year-old man presented with dyspnoea and giddiness on exertion for the last 1 month. A resting ECG during showed trifascicular block with complete right bundle branch block, left anterior fascicular block and a prolonged PR interval of >0.24 s. His echocardiography showed no evidence of wall motion abnormality. He was subjected to a treadmill test for exercise-induced ischaemia, which showed complete atrioventricular (AV) block during first stage of Bruce protocol. His symptoms of dyspnoea and giddiness were also reproduced. The test was terminated and ECG returned to trifascicular block, similar to that at his baseline ECG during recovery. Coronary angiogram (CAG) was performed to rule out any ischaemic cause for this exercise-induced AV block, which was normal. In view of his reproducible symptoms and demonstration of complete AV block on exercise, a dual-chamber pacemaker (DDD) was implanted. His symptoms disappeared and he remained asymptomatic on follow-up.