Vascular disease and stroke risk in atrial fibrillation: a nationwide cohort study.

BACKGROUND: Vascular disease (including myocardial infarction and peripheral artery disease) has been proposed as a less well-validated risk factor for stroke in patients with atrial fibrillation. We investigated whether vascular disease is an independent risk factor of stroke/thromboembolism in atrial fibrillation and whether adding vascular disease improves Congestive heart failure, Hypertension, Age 75 years, Diabetes, previous Stroke (CHADS(2)) risk stratification.

METHODS: By using nationwide Danish registers, we identified all patients discharged with atrial fibrillation and not treated with vitamin K antagonist or heparin between 1997 and 2008. The rate of stroke/thromboembolism in patients with atrial fibrillation with and without vascular disease was determined, and the risk associated with vascular disease was estimated in Cox regression analyses. The value of adding vascular disease to the CHADS(2) score was evaluated by Net Reclassification Improvement and Integrated Discrimination Improvement.

RESULTS: We included 87,202 patients with non-valvular atrial fibrillation; of these, 15,212 (17.4%) had vascular disease, 11,750 (77.2%) had myocardial infarction, 2503 (16.5%) had peripheral artery disease, and 959 (6.3%) had both. In patients with a CHADS(2) score=0, the rate of stroke/thromboembolism at 1-year follow-up was 2.31 (1.63-3.26) and 1.52 (1.34-1.73) per 100 person-years in patients with and without vascular disease, respectively. Vascular disease increased the risk of stroke/thromboembolism in both univariate (hazard ratio [HR] 1.26; confidence interval [CI], 1.18-1.35) and multivariate (HR, 1.12; CI, 1.05-1.21) analyses. The risk of stroke/thromboembolism associated with peripheral artery disease alone (HR, 1.93; CI, 1.70-2.19) was greater than the risk with myocardial infarction alone (HR, 1.12; CI, 1.04-1.21), and vascular disease significantly improved the predictive ability of the CHADS(2) score (Net Reclassification Improvement 0.032, P<.001).

CONCLUSIONS: Vascular disease is an independent predictor of stroke/thromboembolism in atrial fibrillation and improves the predictive ability of the CHADS(2) score.