Abstract 84: Impact Of Gastrointestinal Surgery On Efficacy Of Oral Anticoagulants In Patients With Nonvalvular Atrial Fibrillation: A Nationwide Population-based Study

Introduction: Alteration of the gastrointestinal (GI) tract by resection or bypass surgery might affect the absorption of both warfarin and direct oral anticoagulants (DOACs). The clinical trials of DOACs excluded individuals with altered GI tract, hence there are limited pharmacokinetic data for them. Only several cases have been reported suggesting atrial fibrillation-related stroke due to reduced absorption of DOACs after GI surgery. We aimed to investigate the efficacy of warfarin and DOACs who underwent GI surgery using nationwide population-based data. Methods: This was a retrospective cohort study using claim-based national data from 2013 to 2020 from Korean Health Insurance Review and Assessment Service (HIRA). Patients with nonvalvular AF (NVAF) taking oral anticoagulants (OACs) were included. The patients taking OACs due to other indications than NVAF were excluded. Cox proportional hazard models with time-varying covariates were used to investigate the impact of GI surgery in patients taking warfarin and DOACs. Results: Of the 311,782 patients (mean age 72, male 56.7%) with NVAF, 3,807 underwent GI surgery. Warfarin and DOACs were prescribed in 14.3% and 85.7% of the patients, respectively. Overall, warfarin was associated with a higher risk of ischemic stroke compared with DOACs (hazard ratio [HR] 1.51, 95% confidence interval [CI] 1.44-1.59). In the GI surgery group, the hazard ratio for ischemic stroke for warfarin compared with DOACs was 2.70 (95% CI, 1.63-4.45, Figure). In the no GI surgery group, warfarin also had a higher risk of ischemic stroke compared with DOACs (HR 1.51, 95% CI 1.44-1.59). Among DOAC-treated patients, GI surgery was not associated with a risk of ischemic stroke (HR 0.87, 95% CI 0.67-1.12). Conclusions: DOACs were more effective for stroke prevention than warfarin in patients with NVAF whose GI tracts were altered due to previous surgery. GI surgery did not affect the risk of stroke in patients with NVAF taking DOAC.