Background: Current guidelines recommend the CHA2DS2-VASc score to aid decision making regarding anticoagulation in patients with atrial fibrillation (AF). However, the interaction between exercise capacity (EC) and CHA2DS2-VASc is not well described. We hypothesized that for patients with incident AF, higher EC is associated with lower ischemic stroke rate, irrespective of the CHA2DS2-VASc score.
Methods: This retrospective cohort study included 4,243 patients without a history of AF (mean age 63±12 years; 39% women; 68% white) who underwent clinical treadmill stress testing (ETT) in the Henry Ford Health System from 1991 to 2009, and had incident AF during follow-up (mean time from the ETT to incident AF 5.6 ± 4.1 years). EC was categorized on the basis of peak metabolic equivalents (METs) achieved: < 6, 6 to 9, 10 to 11, and ≥12. The score was calculated at the time of the AF incidence and considered low if it was 0-1 or 0-2 score for men and women, respectively. Multivariable Cox proportional hazards models were used to determine the independent association of EC with post AF stroke and the interaction between CHA2DS2-VASc score and EC in predicting ischemic stroke.
Results: Of the included patients, 3014 (71%) had a high CHA2DS2-VASc score. 847 (20%) patients developed ischemic stroke during the follow-up. EC was significantly lower in patients with incident stroke (mean METs achieved 6.1±2.8 vs. 7.4±3.1; p <0.001). EC category was an independent predictor of incident ischemic stroke after adjusting for confounders including CHA2DS2-VASc score. An increase of 1-MET was associated with 6% lower risk of stroke (95% CI 4-9%). In addition, there is a significant interaction between CHA2DS2-VASc score and EC (p=0.007, figure).
Conclusion: Higher EC was independently associated with a lower risk of ischemic stroke. Our results suggest that even remotely measured EC can be used as a novel risk stratifying strategy for AF patients, even those with low CHA2DS2-VASc score.