Editor's Note: Dr. Olshansky and Dr. Sullivan are members of the ACC Sports & Exercise Cardiology Section and Leadership Council. Now in its second year, the Council is dedicated to the cardiovascular care of athletes, as well as individuals of all ages (pediatric through adult), engaged in exercising.

Atrial fibrillation (AF) has become the most commonly treated arrhythmia but it is rare in the young. In older populations, exercise is associated with a lower relative-risk of new-onset AF.¹ A recent meta-analysis indicated no association between physical activity and risk of AF.² However, the relative-risk of AF increases with exercise frequency.³ Retrospective, longitudinal, case-controlled, and epidemiologic studies, particularly in men, indicate that endurance-type sports are associated with a substantial risk of AF. In a meta-analysis, endurance athletes had an greater risk of AF (odds ratio of 5.29 CI: 3.57 - 7.85, P = 0.0001).⁴ Women athletes may be at lower risk for AF⁵ but not so for men large body size and weight.⁶

The reason endurance athletes appear at high risk of AF may to be due to a complex relationship between arrhythmia triggers and a unique substrate within the athlete heart. Stressors of the sport, including changes in volume status, pH, electrolytes, extremes of temperature, changes in blood pressure, and excessive alterations in autonomic tone can have profound effects on atrial stretch, pressure overload, and pulmonary vein changes leading to AF. Atrial remodeling can occur.^{7, 8} Inflammation is postulated to have a role.^{9, 13, 12} Catecholamine excess may be to blame^{10, 11} especially in light of high baseline of parasympathetic activity.

Work Up of AF in the Athlete

Generally, the athlete comes to medical attention with symptoms, or intolerance of the sport. The number of athletes with undetected AF is unknown. Careful evaluation of underlying cardiac disease is essential; unique conditions such as arrhythmogenic right ventricular and hypertrophic cardiomyopathy, for example, may be associated with AF. When no cardiac condition is diagnosed (generally the case), AF needs to be considered by type (single episode, recurrent paroxysms, persistent episode(s) or longstanding), duration, heart rate and any comorbidity. Attention to the timing of symptoms in relation to sport is necessary.

Other triggers (e.g., thyrotoxicosis, electrolyte abnormality) must be considered. Use of supplements and performance enhancing drugs: androgenic steroids, erythropoiesis stimulating agents, growth hormone, stimulants (e.g., amphetamines and ephedrine), β-2 stimulants (e.g., salbutamol or salmeterol), intoxicants (e.g., alcohol, ketamine, cocaine, ecstasy, marijuana) and diuretics should be ruled out.

AF should be documented but, even before a definitive arrhythmia diagnosis is secured with external (or internal) monitoring, restriction may be necessary if symptoms are severe (extreme dyspnea, fatigue or syncope) especially if endurance or extreme physical activity is required during the sport. Further testing (echocardiography, cardiac catheterization or MRI, for example) is determined based upon clinical findings. Stress testing, approximating the duration and type of exercise performed can help determine if AF is exercise-induced, and the rate, symptoms and hemodynamics during AF.

Managing AF in the Athlete

Management focuses on control of AF and consideration for restriction based on the specific sport, the level of competition and the symptoms. By an unknown mechanism, some athletes may have a controlled ventricular response during AF and remain asymptomatic without medications. Asymptomatic athletes who have short episodes of AF or an isolated potentially explainable episode (even if it requires cardioversion) can participate in sports.

For those with recurrent and highly symptomatic episodes, sport restriction may be necessary. Reduction in athletic activity may reduce the risk of AF. Beta-blockers or calcium antagonists to control rapid ventricular rate may blunt physical performance, yet, not ameliorate symptoms. If utilized, stress testing before a return to sport is in order. The same holds true if an antiarrhythmic drug is prescribed. No antiarrhythmic drug has proven efficacious in the competitive athlete to decrease AF episodes. All effects can be overridden by excess catecholamines. If oral anticoagulation is prescribed based on high-risk of stroke, contact or other sports, in which risk of bleeding is high, should be avoided.

Ablation has an emerging role for the athlete. Ablation of an accessory pathway associated with AF would be expected to be curative.¹⁷ Ablation of associated atrial flutter alone would not.¹⁸ Pulmonary vein isolation via catheter ablation is an emerging technique that has been utilized early in the treatment of the athlete^14-16 especially when no structural heart disease is diagnosed. While the studies are small, follow-up is short, and more than one ablation procedure may be required. Risk of ablation must be weighed carefully against its benefit. Return to sport is possible, but not necessarily guaranteed, after pulmonary vein isolation. Nevertheless, ablation, early in the management of AF can offer the athlete new hope to return to play.

References

1. Mozaffarian D, Furberg CD, Psaty BM, Siscovick D. Physical activity and incidence of atrial fibrillation in older adults: the cardiovascular health study. Circulation. 2008;118:800-7.
2. Ofman P, Khawaja O, Rahilly-Tierney CR, Peralta A, Hoffmeister P, Reynolds MR, Gaziano JM, Djousse L. Regular Physical Activity and Risk of Atrial Fibrillation: A Systematic Review and Meta-Analysis. Circ Arrhythm Electrophysiol. 2013.
3. Aizer A, Gaziano JM, Cook NR, Manson JE, Buring JE, Albert CM. Relation of vigorous exercise to risk of atrial fibrillation. Am J Cardiol. 2009;103:1572-7.
4. Abdulla J, Nielsen JR. Is the risk of atrial fibrillation higher in athletes than in the general population? A systematic review and meta-analysis. Europace. 2009;11:1156-9.
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15. Koopman P, Nuyens D, Garweg C, La Gerche A, De Buck S, Van Casteren L, Alzand B, Willems R, Heidbuchel H. Efficacy of radiofrequency catheter ablation in athletes with atrial fibrillation. Europace. 2011;13:1386-93.
16. Calvo N, Mont L, Tamborero D, Berruezo A, Viola G, Guasch E, Nadal M, Andreu D, Vidal B, Sitges M, Brugada J. Efficacy of circumferential pulmonary vein ablation of atrial fibrillation in endurance athletes. Europace. 2010;12:30-6.
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18. Heidbuchel H, Anne W, Willems R, Adriaenssens B, Van de Werf F, Ector H. Endurance sports is a risk factor for atrial fibrillation after ablation for atrial flutter. Int J Cardiol. 2006;107:67-72.

Keywords: Atrial Fibrillation, Atrial Flutter

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