Effectiveness and safety of rivaroxaban versus warfarin in obese patients with acute venous thromboembolism: analysis of electronic health record data.

There is limited data evaluating clinical outcomes of rivaroxaban versus warfarin in obese patients with venous thromboembolism (VTE). Our objective was to evaluate the effectiveness and safety of rivaroxaban versus warfarin in obese VTE patients. We performed a cohort analysis using Optum® De-Identified Electronic Health Record data from 11/1/2012 to 9/30/2018. Patients with a body mass index (BMI) ≥ 30 kg/m2 admitted to the hospital, emergency department or observation unit for VTE, prescribed rivaroxaban or warfarin as their first oral anticoagulant (OAC) within 7-days and had ≥12-months of EHR activity prior were included. We excluded patients with OAC use at baseline or cancer. Patients were 1:1 matched (standard differences<0.10). Primary outcomes were recurrent VTE and major bleeding at 3-, 6- and 12-months using an intent-to-treat approach. Subanalyses of BMI 30.0-34.9, 35.0-39.9 and ≥ 40 kg/m2 were performed. Risk was compared using Cox regression and reported as hazard ratios (HRs) with 95% confidence intervals (CI). We identified 6755 rivaroxaban and 6755 warfarin users with BMI ≥ 30 kg/m2 and incident VTE. At 3-, 6- and 12-months, rivaroxaban was associated with a reduced hazard of recurrent VTE compared to warfarin (HR 0.61, 95%CI   0.51-0.72; HR 0.65, 95%CI  0.55-0.77; HR 0.63, 95%CI  0.54-0.74) with no difference in major bleeding (HR  0.99, 95%CI  0.68-1.44; HR 0.90, 95%CI  0.64-1.26; HR 1.00, 95%CI  0.73-1.36). No statistical difference was found across BMI categories for either recurrent VTE (p-interaction≥0.43) or major bleeding (p-interaction ≥ 0.58) at any time point. In obese VTE patients, prescription of rivaroxaban was associated with a significantly reduced risk of recurrent VTE versus warfarin, without impacting major bleeding. Our findings remained consistent across BMI classes.