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

Although rivaroxaban has demonstrated consistent drug levels in normal weight and obese patients, sufficient confirmation of equal clinical effectiveness and safety is currently lacking. 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. 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/m 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/m) were performed. Cox regression was performed and reported as hazard ratios (HRs) and 95% confidence intervals (CIs). 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 (-interaction = .58) or major bleeding (-interaction = .44) outcomes. 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.