Patients who have both AFib and moderate-to-severe CKD have been commonly omitted from large trials examining antithrombotic therapy. As a result, the data guiding treatment for patients with both CKD and AFib is limited. This new study found that while warfarin significantly reduced the risk of stroke or systemic thromboembolism in patients with CKD, the bleeding risk increased greatly. On the other hand, aspirin did not reduce the stroke or systemic thromboembolism risk and significantly increased the risk of bleeding. 

"Thus, the net clinical effect of warfarin treatment requires careful assessment in patients with chronic kidney disease, and the data do not provide clear guidance regarding indications for anticoagulant therapy in patients with both atrial fibrillation and chronic kidney disease," the study's authors cautioned. "Ideally, the role of warfarin (or of other, newer anticoagulant agents) in patients with atrial fibrillation who have chronic kidney disease should be evaluated in a clinical trial."