Exercise-Induced Second-Degree Atrioventricular Block in Endurance Athletes

DOUTRELEAU, S., C. PISTEA, E. LONSDORFER, and A. CHARLOUX. Exercise-Induced Second-Degree Atrioventricular Block in Endurance Athletes. Med. Sci. Sports Exerc., Vol. 45, No. 3, pp. 411-414, 2013. Training induces volume-and time-dependent morphological and functional changes in the heart. Heart rhythm disorders, such as atrial arrhythmia (including atrial fibrillation and atrial flutter), are a well-established consequence of such long-term endurance practice. Although resting bradycardia and first-degree atrioventricular persist in veteran athletes, a higher conduction system impairment has never been reported neither at rest nor during exercise. We report here two cases of Type II second-degree atrioventricular block occurring during exercise in middle-age well-trained athletes. Because animal and human studies suggest that a progressive myocardial fibrosis could explain such phenomenon, long-term training could also have consequences on the conduction pathways.