The controversial relationship between exercise and atrial fibrillation:clinical studies and pathophysiological mechanisms

Atrial fibrillation (AF) is the most common clinically significant arrhythmia observed both in the general population and in competitive athletes. Coronary artery disease, hypertension, and diabetes mellitus are among the most important risk factors and are all preventable by regular physical activity. However, while the benefits of moderate physical activity in controlling cardiovascular risk factors and decreasing the risk of AF have been extensively proved, concerns have raised about the potential negative effects of vigorous exercise, particularly in endurance athletes. Furthermore, in a subset of patients with AF younger than 60 years, routine evaluation does not reveal any cardiovascular disease or any other known causal factor. This condition is called “lone AF” and the potential mechanisms underlying this condition are speculative and remain to be clarified. Atrial ectopy, increased vagal tone, changes in electrolytes, left atrial (LA) dilatation and fibrosis have been proposed among others as potential mechanisms. However, no convincing data still exist. Particularly the increase in LA size represents in athletes a physiological adaptation to exercise conditioning and the presence of biatrial fibrosis has not been demonstrated in humans. Thus, contrary to patients with cardiovascular disorders, the atrial substrate seems to play a secondary role in healthy athletes. This review article analyses the controversial relationship between AF and physical activity, with a particular attention to the pathophysiological mechanisms that could be responsible for AF in the athletic population.