Outcomes After Use of Standard- and Low-Dose Non-Vitamin K Oral Anticoagulants in Asian Patients With Atrial Fibrillation

Background and Purpose- Limited data are available describing the relative effectiveness, safety, and optimal dosing of non-vitamin K antagonist oral anticoagulants (NOACs) for treatment of nonvalvular atrial fibrillation in East Asian patients. We tried to compare effectiveness and safety outcomes of standard- and low-dose NOACs and warfarin in this population. Methods- Using nationwide administrative claims-based datasets from the Korean National Health Insurance Service Database (July 1, 2015, to December 31, 2016), this study comprised 56 504 anticoagulation-naive nonvalvular atrial fibrillation patients with high thromboembolic risk (CHA₂DS₂-VASc score, ≥2) treated with oral anticoagulants. Main study outcomes included thromboembolic events (ischemic stroke or systemic embolism), major bleeding, and mortality. Results- Among the study patients, 10 409 (18.4%) received warfarin and 46 095 (81.6%) were treated with NOACs: dabigatran (n=12 593; 22.3%), rivaroxaban (n=21 000; 37.2%), and apixaban (n=12 502; 22.1%). Low-dose NOAC (75.1% dabigatran, 59.7% rivaroxaban, and 62.7% apixaban) was more frequently used than standard-dose NOAC. During median follow-up of 15.0 months, each NOAC was associated with significantly lower risk of thromboembolic events (hazard ratio [HR], 0.76; 95% CI, 0.75-0.81 for dabigatran; HR, 0.74; 95% CI, 0.65-0.83 for rivaroxaban; and HR, 0.68; 95% CI, 0.59-0.78 for apixaban). Regarding safety outcomes, dabigatran (HR, 0.81; CI, 0.69-0.95) and apixaban (HR, 0.67; CI, 0.56-0.79) were associated with lower risk of major bleeding but not with rivaroxaban (HR, 0.96; CI, 0.84-1.11). Among adults <75 years of age without chronic kidney disease, use of low-dose apixaban did not demonstrate clinical benefit over warfarin with respect to thromboembolic events (HR, 0.99; CI, 0.76-1.28) and mortality (HR, 0.85; CI, 0.62-1.16). Conclusions- In this cohort of East Asian patients with nonvalvular atrial fibrillation, NOACs were associated with better effectiveness and safety outcomes versus warfarin. Lower NOAC doses were more often used, but an unjustified underdosing of apixaban seems to result in lower clinical benefit.