Lower-dose warfarin delays renal progression and prolongs patient survival in patients with stage 3 – 5 chronic kidney disease and nonvalvular atrial fibrillation: a 12-year follow-up study

Background Anticoagulants are used to reduce the risk of stroke in patients with atrial fibrillation (Af) and chronic kidney disease (CKD). Warfarin is one of the commonly used anticoagulants; however, its effect on renal function remains unclear. Methods In a retrospective cohort study (January 2001 - July 2013), we surveyed data charts from 2,450 patients with stage 3 - 5 CKD, and enrolled 159 patients with Af. In total, 104 patients had a CHADS2 score of >= 2 (congestive heart failure, hypertension, >= 75 years old, diabetes, 1 point; prior stroke or transient ischemic attack or thromboembolism, 2 points). These patients were categorized into groups A and B based on warfarin treatment. Group A included 73 patients and was not undergoing warfarin treatment and group B included 31 patients undergoing warfarin treatment. The baseline demographic and biochemical data as well as changes in estimated glomerular filtration rate (eGFR) after 6, 12, and 18 months of warfarin treatment were analyzed. We also studied censored patient survival over 12 years using Kaplan-Meier model. Results The mean international normalization ratio (INR) of warfarin treatment in group B was 1.92 ± 1.04. Moreover, group B showed a significant increase in eGFR. The maximum improvement was at 6 months (mean eGFR increased from 25.97 to 31.12 mL/min; p = 0.01) and lasted for up to 18 months (eGFR 28.65 mL/min). Despite higher initial CHADS2 scores, group B showed a superior survival rate compared with group A (p = 0.02). Conclusion Lower doses of warfarin may protect against renal dysfunction and could be beneficial for treatment of stage 3 - 5 CKD with Af.