Renal Function and the Risk of Stroke and Bleeding in Patients With Atrial Fibrillation An Observational Cohort Study

Background and Purpose We sought to determine the risk of stroke/thromboembolism and bleeding associated with reduced renal function in patients with atrial fibrillation and the risk of stroke and bleeding associated with warfarin treatment in specific estimated glomerular filtration rate (eGFR) groups. Methods We conducted a register-based cohort study and included patients discharged with nonvalvular atrial fibrillation from 1997 to 2011 with available eGFR. Results A total of 17349 patients were identified with eGFR available at baseline. All levels of lower eGFR were associated with higher risk of stroke/thromboembolism and bleeding. Use of warfarin was associated with higher bleeding risk in all eGFR groups; hazard ratios 1.23 (95% confidence interval [CI], 0.97-1.56), 1.26 (95% CI, 1.14-1.40), 1.18 (95% CI, 1.07-1.31), 1.11 (95% CI, 0.87-1.42), 2.01 (95% CI, 1.14-3.54) in patients with eGFR 90, 60 to 89, 30 to 59, 15 to 29, and <15 mL/min per 1.73 m(2), respectively. Use of warfarin was associated with lower risk of stroke/thromboembolism in patients with eGFR 15 mL/min per 1.73 m(2); hazard ratios 0.57 (95% CI, 0.43-0.76), 0.57 (95% CI, 0.51-0.64), 0.48 (95% CI, 0.44-0.54), 0.60 (95% CI, 0.45-0.80) in patients with eGFR 90, 60 to 89, 30 to 59, and 15 to 29 mL/min per 1.73 m(2), respectively. Use of warfarin was not associated with lower risk of stroke/thromboembolism in patients with eGFR<15 mL/min per 1.73 m(2); hazard ratio 1.18 (95% CI, 0.58-2.40). Conclusions In patients with atrial fibrillation, the risk of stroke and bleeding was associated with levels of renal function. Warfarin treatment was associated with higher risk of bleeding in all eGFR groups and lower risk of stroke in patients with eGFR15 mL/min per 1.73 m(2).