While there are gaps in the evidence related to epidemiology and mechanisms of atrial fibrillation (AFib), these patients should be encouraged to be physically active with moderation, according to a state-of-the-art review published online Aug. 30 in JACC: Clinical Electrophysiology.

N. A. Mark Estes III, MD, FACC, and Christopher Madias, MD, examined whether exercise is detrimental to patients with AFib and found a considerable body of evidence supporting an increased incidence of AFib in high-intensity endurance athletes. The frequency of AFib is estimated to be between two and 10 times greater in high-intensity endurance athletes than in sedentary individuals, but much of this evidence is retrospective and observational. Much of the data have been largely focused on men, and recent evidence suggests there might be a sex-specific effect.

While there are multiple knowledge gaps regarding pathophysiologic mechanisms underlying the development of AFib in athletes, proposed mechanisms include alterations of autonomic tone, left atrial enlargement and fibrosis, electrical remodeling and increased inflammation. Studies have shown that at rest and during low intensity physical activity, endurance athletes have dominant vagal tone compared with non-athletes. Additionally, mechanical as well as electrophysiologic remodeling have been noted in endurance athletes.

It is common to recommend that athletes with symptomatic AFib reduce the duration and intensity of exercise for up to three months to assess the relationship between exercise and AFib. If this results in a meaningful decrease in AFib, it is reasonable to allow resumption of less intense exercise and reassess the symptoms related to AFib. However, if an athlete chooses not to reduce their exercise, it is reasonable for physicians to respect the athlete's decision and advance alternate therapeutic approaches for the AFib. Recommendations regarding continued sports participation for the competitive athlete have been recently updated and can guide clinicians in advising athletes with AFib. Of note, athletes with AFib that is well tolerated and self-terminating may participate in competitive sports without the need for any therapy.

"Clinicians must use the limited, but best available data to manage these patients," the authors write. "To the extent that the cardiovascular benefits of exercise are well established, all patients should be encouraged to be physically active with moderation. The evidence is conclusive that sedentary lifestyles contribute to AFib development independent of gender. Physical activity in moderation decreases the risk of AFib in men and women; however, men should be advised of the potentially increased risk of AF with long term, high-intensity endurance training."

Keywords: Athletes, Atrial Remodeling, Sedentary Behavior, Incidence, Atrial Fibrillation, Retrospective Studies, Physical Endurance, Sports, Exercise, Rest, Inflammation, Electrophysiology

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