Cardioversion and the Risk of Subsequent Stroke or Systemic Embolism and Death in Emergency Department Patients With Acute Atrial Fibrillation or Flutter

Objectives Guideline recommendations for the emergency department cardioversion of patients with acute atrial fibrillation/flutter have recently changed. This was related to several studies that found a higher-than-expected risk of subsequent stroke or systemic embolism in cardioverted atrial fibrillation/flutter patients. We sought to confirm an elevated rate of stroke, systemic embolism, or death following emergency department cardioversion to normal sinus rhythm compared with similar patients who were not converted. Methods This retrospective cohort study combined 4 datasets of atrial fibrillation/flutter patients seen at 25 emergency departments in Ontario, Canada, 2000-2012, who were all eligible for cardioversion. We linked patients to province-wide datasets to determine the primary outcome, a composite of stroke, systemic embolism, or all-cause death. To adjust for baseline differences between patients who cardioverted vs those who did not, we used overlap weights based on the propensity score. The latter included 28 variables, including oral anticoagulant prescriptions. Results Of 2521 patients, 2060 (81.7%) converted to sinus rhythm in the emergency department, and 1055 (41.8%) left on anticoagulation. Twelve (0.48%) patients met the primary outcome at 30 days and ≤5 (≤0.2%) at 7 days. In the weighted sample, at 30 days, the primary outcome occurred in 0.37% (95% CI, 0.04%-0.78%) of cardioverted patients vs 0.23% (95% CI, 0.00%-0.60%) in those not cardioverted; the absolute risk increase was 0.13% (95% CI, −0.36% to 0.69%; P = .61), and the number needed to harm was 747. Conclusion In atrial fibrillation/flutter patients eligible for cardioversion at 25 emergency departments, the rate of subsequent stroke or systemic embolism and death was very low. After adjusting for risk factors and post-conversion oral anticoagulant use, the rate of subsequent stroke and systemic embolism and death was not significantly higher in patients who cardioverted vs those who did not.