Warfarin Benefits Patients with Atrial Fibrillation and CKD

Across the range of kidney function levels, warfarin therapy improves survival and reduces adverse events in patients with atrial fibrillation, reports a study in the Journal of the American Medical Association.

The researchers identified 24,317 Swedish patients with atrial fibrillation and a history of acute myocardial infarction. On the basis of serum creatinine levels, 51.7 percent of patients had CKD: estimated GFR (eGFR) less than 60 mL/min/1.73 m2. At discharge, 21.8 percent of patients had a prescription for warfarin. Outcomes associated with warfarin therapy were analyzed for groups at different levels of kidney function.

At 1 year, rates of a composite outcome of death, myocardial infarction, or stroke were significantly lower among patients receiving warfarin. Adjusted hazard ratios among warfarin-treated patients were 0.73 at an eGFR of greater than 60 mL/min/1.73 m2, 0.73 between 30 and 60 mL/min/1.73 m2, 0.84 between 15 and 30 mL/min/1.73 m2, and 0.57 at less than 15 mL/min/1.73 m2. Across kidney function groups, there was no warfarin-related increase in bleeding risk.

Warfarin therapy was also associated with a reduction in the combined rate of the primary composite outcome and the bleeding outcome. The adjusted hazard ratios were 0.76 at an eGFR of greater than 60 mL/min/1.73 m2, 0.75 between 30 and 60 mL/min/1.73 m2, 0.82 between 15 and 30 mL/min/1.73 m2, and 0.55 at 15 mL/min/1.73 m2 or less.

An increasing number of patients have concomitant CKD and atrial fibrillation. There are conflicting data on the benefits and safety of warfarin for patients with CKD; trials of anticoagulation therapy have excluded patients with reduced kidney function.

In this large Swedish cohort study, warfarin reduced the risk of death, myocardial infarction, or ischemic stroke in patients with concomitant atrial fibrillation and CKD without increasing bleeding risk. Benefits were noted at all levels of eGFR. Reduced kidney function is not a reason to deny warfarin therapy in patients with atrial fibrillation and established cardiovascular disease, the authors suggest [Carrero JJ, et al. Warfarin, kidney dysfunction, and outcomes following acute myocardial infarction in patients with atrial fibrillation. JAMA 2014; 311:919–928].