Atrial Fibrillation in Endurance Athletes

PM&R News   •   December 2018

With “Holiday Heart” season upon us, it seems appropriate to have a discussion about Atrial fibrillation. Atrial fibrillation (AF) is most commonly seen in older men and is generally associated with cardiac risk factors including hypertension and coronary artery disease leading to structural changes in the heart. However, several studies have also identified an association of paroxysmal AF in young to middle aged endurance athletes. So, if you were planning to keep your heart healthy this holiday season with marathon training or 100-mile bike rides, you may not be completely out of the woods.

The higher incidence of AF in endurance athletes has been specifically observed in males, although it is unclear if the effect also occurs in women due to insufficient data. In most of the studies performed, high intensity endurance athletes (i.e running, cycle, cross-country skiing, rowing) were compared against a control of non-endurance athletes (i.e. golf). Significantly, mild to moderate exercise is associated with a decreased risk of AF, suggesting exercise may be on a bell-shaped curve. The cumulative number of intensity minutes and shortened recovery times point to an increased risk of AF. Several mechanisms have been proposed to explain this association, but the exact pathophysiology remains uncertain. One mechanism investigated is a correlation between left atrial dilation and endurance athletes. Left atrial (LA) dilation in endurance athletes is likely due to increased pulmonary pressures found during exercise, which lead to increased left atrial pressure and subsequent dilation. This sounds plausible, but when athletes with observed LA dilation were compared to those without, no significant difference was found in the number of AF events that occurred. Another mechanism that has been proposed is inadequate recovery between high intensity events leading to fibrosis and inflammation in the atrium, which serves as a substrate for AF. An additional contributing factor may be the increased parasympathetic tone found at rest in endurance athletes. This high vagal tone leads to sinus bradycardia which may be the trigger for AF. Ultimately, the process leading to AF in athletes is likely multifactorial and will continue to be a topic of research.

What does this mean clinically? A thorough history and work-up should be done initially to exclude alternate causes of AF (such as WPW, hyperthyroidism, heart disease, etc). Once complete, the guidelines for treatment remain similar to those in the general population – rate vs rhythm control. The endurance athletes’ preference, however, will likely vary. Beta-blocker therapy is poorly tolerated because it impairs the athletes’ ability to compete at high levels. De-training has also been proposed, but most athletes have not been interested in this solution. The most popular treatment in this population is ablation therapy. With ablation therapy, the athlete can return to their sport without the need for medications. As far as anticoagulation, CHA₂DS₂-VASc score should be used to risk stratify each individual. Most young to middle aged athletes will have a score of 0, resulting in no anticoagulation.

Contributing Author: Malia Cali, MD