Effectiveness and safety of rivaroxaban versus warfarin in obese nonvalvular atrial fibrillation patients: analysis of electronic health record data.

Background: Although rivaroxaban has demonstrated consistent drug levels in normal weight and obese patients, sufficient confirmation of equal clinical effectiveness and safety is currently lacking.Purpose: To evaluate the effectiveness and safety of rivaroxaban versus warfarin for prevention of stroke and systemic embolism (SSE) in obese nonvalvular atrial fibrillation (NVAF) patients.Methods: Using Optum de-identified Electronic Health Record (EHR) data from November 2011 to September 2018,we evaluated NVAF patients with a body mass index (BMI)≥30 kg/m2 newly initiated on rivaroxaban or warfarin (index date), with ≥12-months of EHR activity and ≥1 encounter before the index date. We excluded patients with valvular disease or evidence of oral anticoagulant (OAC) use at baseline. Patients who were prescribed rivaroxaban were 1:1 propensity-score matched to patients who were prescribed warfarin (standard differences <0.10 achieved for all covariates). Outcomes included SSE and major bleeding using an intent-to-treat approach. Subanalyses stratified by BMI (30.0-34.9, 35.0-39.9 and ≥40 kg/m2) were performed. Cox regression was performed and reported as hazard ratios (HRs) and 95% confidence intervals (CIs).Results: We included 35,613 rivaroxaban and 35,613 warfarin users with NVAF. Patients were followed for a median of 2.6 years (25%-75% range = 1.2-4.1). Rivaroxaban was associated with a reduced risk of SSE (HR = 0.83, 95%CI = 0.73-0.94) and major bleeding (HR = 0.82, 95%CI = 0.75-0.89) compared to warfarin. Subanalysis did not show a statistically significant interaction across BMI categories for SSE (p-interaction = .58) or major bleeding (p-interaction = .44) outcomes.Conclusions: Among obese NVAF patients, prescription of rivaroxaban was associated with a reduced risk of SSE and major bleeding compared to warfarin, which remained consistent across BMI classes.