Warfarin associated with lower stroke, systemic thromboembolism risk in patients with both afib and CKD

The addition of chronic kidney disease (CKD) to atrial fibrillation is associated with an increased risk of stroke or systemic thromboembolism and bleeding. Warfarin treatment was associated with decreasing this risk, a new study found.

Researchers collected data on all patients discharged from Danish hospitals with a diagnosis of nonvalvular atrial fibrillation between 1997 and 2008. Of the more than 130,000 patients studied, 2.7% had non-end-stage CKD and an additional 0.7% were on renal-replacement therapy at the time of hospitalization.

The study was published in the New England Journal of Medicine on Aug. 16.

The kidney disease and atrial fibrillation patients had a significantly increased risk of stroke or systemic thromboembolism compared to those with only atrial fibrillation (hazard ratio for non-end-stage group, 1.49; 95% CI, 1.38 to 1.59; hazard ratio for renal-replacement group, 1.83; 95% CI, 1.57 to 2.14). Taking warfarin appeared to reduce this risk (to a similar degree as in non-kidney-disease patients), but aspirin did not. The kidney disease group also had an increased risk of bleeding, which was further increased by both aspirin and warfarin.

The risk of stroke and thromboembolism was not affected by the severity of the kidney disease, the researchers noted, but the bleeding risk increased with larger doses of loop diuretics. Because warfarin was found both to reduce clot risk and increase bleeding risk, careful assessment is required to determine its likely effects in individual patients with kidney disease, the authors said. A clinical trial should be conducted to more precisely determine the effects of warfarin in these patients.

The authors also called for clinical trials of oral anticoagulants in patients with chronic kidney disease. Thus far, trials of these new drugs have largely excluded patients with kidney disease. The authors cautioned that their conclusions were limited by the observational nature of the trial and the availability of over-the-counter aspirin, among other factors.