BACKGROUND Atrial fibrillation, the most common cardiac arrhythmia, is associated with an elevated thromboembolic risk, including ischemic stroke. Guidelines recommend the stratification of individual stroke risk and tailored antithrombotic therapy. This study investigated the demographics, comorbidities, and prognosis of non-valvular AF (NVAF) in Korean patients.

METHODS AND RESULTS We extracted data on 10,846 patients with newly diagnosed NVAF who were naïve to oral anticoagulants from the National Health Insurance Service-National Sample Cohort. CHADS₂and CHA₂DS₂-VASc scores were calculated for each subject using claims data. The study endpoints were ischemic stroke, thromboembolism, and mortality. Mean age was 63.7 years, and 46.8% of the patients were women. Women were older and had higher CHADS₂and CHA₂DS₂-VASc scores. During 30,138 person-years of follow-up, ischemic stroke occurred at a rate of 2.95/100 person-years. CHADS₂and CHA₂DS₂-VASc scores showed good performance in risk prediction. CHA₂DS₂-VASc score performed better at discriminating stroke risk in patients with low-risk profiles. The presence of female sex and vascular disease added little improvement in risk prediction.

CONCLUSIONS Korean NVAF patients had high risk of stroke and mortality, and had multiple comorbidities. While both CHADS₂and CHA₂DS₂-VASc schema had good performance in risk prediction, CHA₂DS₂-VASc score was superior in identifying truly low-risk patients. Given that Asian ethnicity is associated with bleeding events, individualized accurate risk prediction is necessary to improve patient outcomes.