March 4th, 2014
AF Patients with Chronic Kidney Disease Also Benefit from Warfarin
Larry Husten, PHD
Anticoagulation is a cornerstone of therapy for atrial fibrillation because it lowers the heightened risk for stroke in this population. People with chronic kidney disease are also at increased risk for stroke, but the benefits of anticoagulation are less clear in this group, and anticoagulation is used less often in AF patients who have CKD. Now, a large observational study offers some reassurance that anticoagulation in AF patients with CKD may be beneficial.
Researchers in Sweden analyzed data from more than 24,000 survivors of acute myocardial infarction who had AF. In a paper published in JAMA, they report that more than half (51.7%) of this group had CKD (stage 3 or above). More than a fifth (21.8%) of all patients were treated with warfarin, and after 1 year of follow-up, these patients had a lower rate of death, MI, or stroke but no significant increases in bleeding complications. The findings persisted after the researchers adjusted for differences between the groups. Severity of CKD did not affect the results.
In an accompanying editorial, Wolfgang Winkelmayer and Mintu Turakhia discuss some of the limitations of the study, including “the central issue of confounding by indication for warfarin treatment.” They also point out that INR control in Sweden is the best in the world, so the results of the study may not apply where warfarin is not optimally employed. In addition, they caution that the results should not be generalized to AF patients who have not had an MI.
Nevertheless, they write, the study “provides the best evidence to date that vitamin K antagonists are associated with improved clinical outcomes and no significant increased risk of bleeding in patients with myocardial infarction and atrial fibrillation with advanced CKD. These data support the use and continuation of warfarin therapy among patients with CKD with excellent INR control.”
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The evidence remains lacking in patients on dialysis.
The take home message here is those who suffered an MI and has AF in addition to CKD ..warfarin therapy can reduce their risk of stroke/MI/Death without increased risk of bleeding if therapy is done in nearly perfect conditions with excellent control of INR like in Sweeden. Whether these results still apply to every day practice such as those with AF and CKD with no history of MI or in those without adequate control of their INR is unclear yet and needs further study.