Impact of renal function on ischemic stroke and major bleeding rates in nonvalvular atrial fibrillation patients treated with warfarin or rivaroxaban: a retrospective cohort study using real-world evidence

Objectives: Renal dysfunction is associated with increased risk of cardiovascular disease and is an independent predictor of stroke and systemic embolism. Nonvalvular atrial fibrillation (NVAF) patients with renal dysfunction may face a particularly high risk of thromboembolism and bleeding. The current retrospective cohort study was designed to assess the impact of renal function on ischemic stroke and major bleeding rates in NVAF patients in the real-world setting (outside a clinical trial). Methods: Medical claims and Electronic Health Records were retrieved retrospectively from Optum's Integrated Claims-Clinical de-identified dataset from May 2011 to August 2014. Patients with NVAF treated with warfarin (2468) or rivaroxaban (1290) were selected. Each treatment cohort was stratified by baseline estimated creatinine clearance (eCrCl) levels. Confounding adjustments were made using inverse probability of treatment weights (IPTWs). Incidence rates and hazard ratios of ischemic stroke and major bleeding events were calculated for both cohorts. Results: Overall, patients treated with rivaroxaban had an ischemic stroke incidence rate of 1.9 per 100 person-years (PY) while patients treated with warfarin had a rate of 4.2 per 100 PY (HR = 0.41 [0.21-0.80], p = .009). Rivaroxaban patients with an eCrCl below 50mL/min (N = 229) had an ischemic stroke rate of 0.8 per 100 PY, while the rate for the warfarin cohort (N = 647) was 6.0 per 100 PY (HR = 0.09 [0.01-0.72], p = .02). For the other renal function levels (i.e. eCrCl 50-80 and >= 80 mL/min) HRs indicated no statistically significant differences in ischemic stroke risks. Bleeding events did not differ significantly between cohorts stratified by renal function. Conclusions: Ischemic stroke rates were significantly lower in the overall NVAF population for rivaroxaban vs. warfarin users, including patients with eCrCl below 50 mL/min. For all renal function groups, major bleeding risks were not statistically different between treatment groups.