Risk of ischemic stroke after atrial fibrillation diagnosis: A national sample cohort

Atrial fibrillation (AF) is a major risk factor for ischemic stroke and associated with a 5-fold higher risk of stroke. In this retrospective cohort study, the incidence of and risk factors for ischemic stroke in patients with AF were identified. All patients (≥30 years old) without previous stroke who were diagnosed with AF in 2007-2013 were selected from the National Health Insurance Service-National Sample Cohort. To identify factors that influenced ischemic stroke risk, Cox proportional hazard regression analysis was conducted. During a mean follow-up duration of 3.2 years, 1022 (9.6%) patients were diagnosed with ischemic stroke. The overall incidence rate of ischemic stroke was 30.8/1000 person-years. Of all the ischemic stroke that occurred during the follow-up period, 61.0% occurred within 1-year after AF diagnosis. Of the patients with CHA2DS2-VASc score of ≥2, only 13.6% were receiving warfarin therapy within 30 days after AF diagnosis. Relative to no antithrombotic therapy, warfarin treatment for >90 days before the index event (ischemic stroke in stroke patients and death/study end in non-stroke patients) associated with decreased ischemic stroke risk (Hazard Ratio = 0.41, 95%confidence intervals = 0.32-0.53). Heart failure, hypertension, and diabetes mellitus associated with greater ischemic stroke risk. AF patients in Korea had a higher ischemic stroke incidence rate than patients in other countries and ischemic stroke commonly occurred at early phase after AF diagnosis. Long-term (>90 days) continuous warfarin treatment may be beneficial for AF patients. However, warfarin treatment rates were very low. To prevent stroke, programs that actively detect AF and provide anticoagulation therapy are needed.