Athletes and Atrial Fibrillation: No Longer Synonymous?

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For the longest time, cardiologists have accepted the axiom that athletes who exercise vigorously have a higher incidence of atrial arrhythmias, such as atrial fibrillation (AF). A recent observational study published in JAMA Cardiology, however, challenges this long-standing association and makes us question just how much these two actually go hand-in-hand.

In this observational study of 6813 Spanish athletes with a mean age of 22 years, only 21 (0.3%) developed AF during a ~20-year study (1997-2017); predictors of increasing AF risk were increasing age (OR 1.07); years of competition (OR 1.14); and left atrial anteroposterior diameter (OR 1.21), which was the strongest predictor, in multivariate analysis.¹ The study population was 35% women and only 1 of the 21 individuals who developed AF was a woman. Most or all sports disciplines were represented with 28% participating in endurance sports (running, triathlons), 25% in power/sprint sports (such as weightlifting), and 47% in mixed sports. Of those who developed AF, 85.7% of the AF was paroxysmal, 4.8% was persistent and 9.5% was long-standing persistent.¹

Volume vs pressure overload

Many hemodynamic changes can occur with exercise. Endurance sports are a volume overload challenge on the heart and create cardiac chamber dilation. Resistance sports (ie, weightlifting), on the other hand, place a pressure overload challenge on the heart and induce chamber remodeling akin to other pressure overload situations (such as left ventricular hypertrophy from aortic stenosis or hypertension). Yet, both types of athletic endeavor can result in atrial dilation, which is considered a physiologic, nonpathologic cardiac adaption to exercise; previous studies have shown that left atrial enlargement occurs in proportion to lifetime training hours, type of sport, and level of competition. In fact, the “normal” range of left atrial size is actually higher for athletes compared to non-athletes.² However, as this study highlights, even though this left atrial change is considered physiologic, it may be the strongest marker of risk.

The take home-we ought to consider monitoring or screening athletes for left atrial chamber remodeling more regularly so that we can better refine prediction of risk for incident AF. 

A caveat to keep in mind with respect to this study is that AF screening detection was done by baseline and/or exercise ECG or with 24-hour Holter monitor. These screening technologies do have limited sensitivity and longer screening modalities may indeed yield a higher rate of AF,  particularly because the majority of AF detected was paroxysmal.

References:

1. Boraita A, Santos-Lozano A, Heras ME, et al. Incidence of atrial fibrillation in elite athletes. JAMA Cardiol.Published online October 31, 2018. doi:10.1001/jamacardio.2018.3482.

2. D'Ascenzi, Flavio et al. Atrial enlargement in the athlete’s heart: assessment of atrial function may help distinguish adaptive from pathologic remodeling. J Am Soc Echocardiogr. 2018;31:148-157.