Atrial Fibrillation in Athletes - The Story Behind The Running Hearts.

Atrial fibrillation (AF) is the most commonly encountered arrhythmia in clinical practice but the mechanisms underlying the initiation and maintenance of AF are yet to be clarified. It is wellknown that regular exercise is beneficial to health and reduces the risks of cardiovascular diseases. However, recent studies suggest that long-term endurance exercise, including running, swimming, rowing and cycling, or vigorous competitive sports may increase the incidence of AF in these athletes.1-3 Since different studies used different criteria to define the intensity of exercise, the association between exercise and AF in people who exercise simply for fitness is not well established. For instance, in the Cardiovascular Health Study, the incidence of AF in older adults (>65 years old) was lower with moderate-intensity but not high-intensity exercise.4 In the Physician Health Study, vigorous exercise, defined as any exercise strenuous enough to break sweat, was associated with an increase in the incidence of AF only in joggers younger than 55 years old.5 However, how much exercise is too much remains debatable. This review article is intended to provide a summary of the possible links between vigorous exercise and AF that occurs in endurance or competitive athletes. Exercise and AF