To the Editor.—
Dr Dunn1 raised the possibility of atrioventricular nodal dysfunction in a 63-year-old wind-surfer whose ventricular response to atrial fibrillation was only 80 beats per minute. An additional explanation for the slow ventricular response is enhanced vagal tone, a common physiological effect of exercise training. Our clinical experience suggests that a slow ventricular response to atrial fibrillation is the rule rather than the exception in such endurance-trained patients.
Thompson PD. Paroxysmal Atrial Fibrillation in a Physically Active Man. JAMA. 1988;260(20):3006. doi:10.1001/jama.1988.03410200049019