Self-cardioversion of paroxysmal lone atrial fibrillation with exercise.

To the Editor: Endurance athletes may be at increased risk for lone atrial fibrillation.1–5 We describe a middle-aged physician athlete with paroxysmal lone atrial fibrillation in whom cardioversion consistently occurs with vigorous exercise. At 45 years of age, the patient had atrial fibrillation at an average ventricular rate of approximately 55 beats per minute. The results of physician examination, echocardiography, tests of thyroid function, and measurements of electrolytes were normal. After 24 hours of observation, external electrical cardioversion was attempted at progressive energy levels up to 400 J, without success. The patient was discharged home with instructions to take . . .