Endurance Exercise Elevates Atrial Fibrillation Risk

Is moderation the key to all things, including exercise?

While moderate exercise has proven health benefits, such as reduced mortality, an article published ahead of print in Current Opinion in Cardiology suggests endurance exercise sets the stage for cardiomyopathy.

With its potential to increase cardiac output 6-fold, endurance exercise appears to raise the risk of atrial fibrillation (AF) later in life. Of note, AF in athletes is less likely to be associated with common AF risk factors.

Previous research has demonstrated that intense exercise bestows only modest incremental health benefits, while also inducing cardiac remodeling and negating some of the cardiovascular benefits of modest exercise. Thus, exercise is similar to many drugs in that it has an apparent dose-response relationship that exhibits a U-shaped curve, with either no or extreme exercise being associated with poor cardiac outcomes. As exercise intensity and duration increase, so does left atrial dilatation.

In the current study, researchers from 2 Canadian universities documented how observational studies have suggested that repeated strenuous endurance exercise overloads the atria, creating stretch-induced microtears, inflammation, and endocardial scarring. These consequences have been confirmed in animal models, identifying endurance exercise as a causative factor for AF.

The optimal dose of exercise for cardiovascular protection appears to be below what is needed for peak cardiovascular performance. Because it is clear that endurance exercise increases the risk for future AF, and AF represents a cardiac-overuse injury, researchers are now trying to identify the harm threshold.

Treating AF in athletes requires clinicians to understand their needs. Anecdotal evidence has indicated that athletes prefer to avoid drug therapy, and the most promising AF treatment for them is catheter ablation. Ironically, athletes usually seek care so they can return to endurance exercise.