Using the CHA2DS2-VASc Score for Refining Stroke Risk Stratification in 'Low-Risk' Asian Patients With Atrial Fibrillation

BACKGROUND A new scoring system, the anticoagulation and risk factors in atrial fibrillation (ATRIA) score, was proposed for risk stratification in patients with atrial fibrillation (AF). Whether the ATRIA scheme can adequately identify patients who are at low risk of ischemic stroke remains unknown. OBJECTIVES The goal of the present study was to compare the performance of ATRIA to that of CHA(2)DS(2)-VASc (congestive heart failure, hypertension, age >= 75, diabetes mellitus, prior stroke or transient ischemic attack, vascular disease, age 65 to 74, female) scores for stroke prediction. METHODS This study used the National Health Insurance research database in Taiwan. A total of 186,570 AF patients without antithrombotic therapy were selected as the study cohort. The clinical endpoint was the occurrence of ischemic stroke. RESULTS During the follow-up of 3.4 +/- 3.7 years, 23,723 patients (12.7%) experienced ischemic stroke. The CHA(2)DS(2)-VASc score performed better than ATRIA score in predicting ischemic stroke as assessed by c-indexes (0.698 vs. 0.627, respectively; p < 0.0001). The CHA(2)DS(2)-VASc score also improved the net reclassification index by 11.7% compared with ATRIA score (p < 0.0001). Among 73,242 patients categorized as low-risk on the basis of an ATRIA score of 0 to 5, the CHA(2)DS(2)-VASc scores ranged from 0 to 7, and annual stroke rates ranged from 1.06% to 13.33% at 1-year follow-up and from 1.15% to 8.00% at 15-year follow-up. The c-index of CHA(2)DS(2)-VASc score (0.629) was significantly higher than that of the ATRIA score (0.593) in this "low-risk" category (p < 0.0001). CONCLUSIONS Patients categorized as low-risk by use of the ATRIA score were not necessarily low-risk, and the annual stroke rates can be as high as 2.95% at 1-year follow-up and 2.84% at 15-year follow-up. In contrast, patients with a CHA(2)DS(2)-VASc score of 0 had a truly low risk of ischemic stroke, with an annual stroke rate of approximately 1%. (C) 2014 by the American College of Cardiology Foundation.