Perspective:

It is noteworthy that a simple treadmill test may be helpful in predicting the patient’s risk of AF during long-term follow-up. However, the mechanisms underlying the inverse relationship between fitness and AF risk remain unclear. AF is perpetuated by structural remodeling of the atria, manifested by fibrosis, which not only affects the left atrium, but also other atrial regions, such as the sinus node. It is possible that some patients with poor CRF were unable to exercise further due to chronotropic incompetence, in addition to other causes, such as deconditioning and coexisting comorbidities. Recent studies have also suggested that elite athletes may be more likely to develop AF. The current study cannot address this finding since such individuals would be very unlikely to have been referred for exercise testing.