Switching from warfarin to a DOAC in frail elderly asian patients with atrial fibrillation: a nationwide population-based study

Abstract Background Recently, switching international normalized ratio guided warfarin management to a direct oral anticoagulant (DOAC) was associated with more bleeding complications than maintaining warfarin in frail elderly patients with atrial fibrillation (AF). However, there is a paucity of information on whether these results could be applied to Asian patients with AF, who are known to have relatively low time in therapeutic range (TTR) levels. Purpose To evaluate the safety and effectiveness of switching from warfarin to a DOAC in frail elderly Asian patients with AF. Methods Using a Korean health insurance database, we included patients with AF who were prescribed warfarin between January 2013 and August 2015 without significant bleeding or thromboembolic events during the window period, specifically those aged 75 or older with a Hospital Frailty Risk Score of 5 or more. Those who switched to DOACs during the window period were categorized as the DOAC group and those who continued with warfarin were categorized as the warfarin group. The primary outcome was defined as the composite of major bleeding (MB) and clinically relevant non-major bleeding (CRNMB), and secondary outcomes were defined as thromboembolic events, all-cause death, the composite of MB, CRNMB and ischemic stroke (so-called net clinical outcome [NCO]). The propensity score weighting method was utilized to compare the two groups. Results A total of 12,162 patients were included (8,108 with maintaining warfarin, 4,054 with switching to a DOAC). Baseline characteristics were well-balanced after the inverse probability of treatment weighting (mean age, 80 years; men, 50%; and mean CHA₂DS₂-VASc score, 5.6). Compared with maintaining warfarin, switching to a DOAC was associated with significantly higher risks of the primary outcome (hazard ratio [HR] 1.43, 95% confidence interval [CI] 1.09-1.87, p=0.01), thromboembolic events (1.28, 1.01-1.62, p=0.039), all-cause death (1.38, 1.15-1.66, p<0.001) and the NCO (1.26, 1.01-1.58, p=0.04). (Figure A, Figure B), whereas there was no difference in the risk of intracerebral hemorrhage (0.90, 0.50-1.60, p=0.7157). When comparing each DOAC with maintaining warfarin, switching to rivaroxaban was associated with a higher risk of the composite of MB and CRNMB (1.91, 1.38-2.64, p<0.001) and thromboembolic events (1.40, 1.03-1.91, p=0.034) than maintaining warfarin. Conclusion In line with the non-Asian population, switching to a DOAC was associated with a significantly higher risk of MB or CRNMB, thromboembolic events, all-cause death and NCO compared with maintaining warfarin in frail elderly Asian patients with AF. Therefore, even in Asians, switching to a DOAC should be considered more cautiously in patients who are stably managed on warfarin.