Increased risk of ischemic stroke and systemic embolism in hyperthyroidism-related atrial fibrillation: A nationwide cohort study.

Abstract Objective We aimed to evaluate the long-term risk of ischemic stroke/systemic embolism of hyperthyroidism-related AF. Methods This retrospective population-based cohort study included records of 1,034,099 atrial fibrillation patients between 2005 and 2016 from the Korean National Health Insurance Service database. After exclusion, we identified 615,724 oral anticoagulation-naive patients aged ≥18 years with new-onset non-valvular atrial fibrillation, of whom 20,773 had hyperthyroidism-related atrial fibrillation. After 3:1 propensity score matching, ischemic stroke and systemic embolism occurrences were compared between hyperthyroidism-related and non-hyperthyroidism-related (“nonthyroidal”) atrial fibrillation patients. Results After exclusion, we identified 615,724 oral anticoagulation-naive AF patients of whom 20,773 had hyperthyroidism-related AF. Median follow-up duration was 5.9 years. Hyperthyroidism-related AF patients had significantly higher risks of ischemic stroke and systemic embolism than nonthyroidal AF patients (1.83 vs. 1.62 per 100-person year, hazard ratio[HR], 1.13; 95% confidence interval[CI], 1.07 to 1.19; P Conclusion Hyperthyroidism-related AF patients have high risks of ischemic stroke and systemic embolism like nonthyroidal AF, especially when initially diagnosed. This risk is reduced by treating hyperthyroidism.