Warfarin Benefits AFib Patients with Chronic Kidney Disease

A new observational study suggests the use of warfarin may be beneficial for atrial fibrillation patients who also have chronic kidney disease.

To study outcomes associated with warfarin treatment in relation to kidney function in patients with established cardiovascular disease and atrial fibrillation, a team led by researchers from the Karolinska Institutet in Stockholm, Sweden analyzed data from more than 24,000 survivors of acute myocardial infarction who also had atrial fibrillation. Among these patients, more than half had chronic kidney disease—stage 3 or worse. More than one-fifth of all patients (5,292 in total) were treated with warfarin.
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After 1 year of follow-up, the patients receiving warfarin experienced a lower death rate, myocardial infarction, or stroke, but saw no substantial increases in bleeding complications, in comparison to those not receiving warfarin. The severity of patients’ chronic kidney disease did not affect the results, according to the study authors.

The study was undertaken due to “an important knowledge gap” regarding the safety and effectiveness of common drugs in individuals with chronic kidney disease, says Juan-Jesus Carrero-Roig, PhD, a research associate in the department of molecular medicine and surgery at the Karolinska Institutet, and lead study author.

As kidney dysfunction interferes with drug metabolism and drug elimination, patients with kidney dysfunction have traditionally been excluded from randomized controlled trials, explains Carrero-Roig.

“Yet,” he says, “practice guidelines are extrapolated afterwards to those in the absence of formal evaluation.

“We observed that more than 50 percent of the included patients were considered to have moderate chronic kidney disease or worse, evidencing the commonness of kidney dysfunction in individuals with cardiovascular disease,” continues Carrero-Roig, who describes the association between warfarin treatment and a lower risk for the composite outcome without increased risk of bleeding as the study’s “main finding.”

The study included individuals with kidney disease who do not require dialysis, he adds, noting that the evaluation of warfarin safety in dialysis patients has yet to be fully established.

For primary care practitioners, “the most important message is that warfarin/coumarin treatment also works in patients with reduced kidney function,” says Jonas Spaak, MD, PhD, a clinical researcher in cardiology at the Danderyd University Hospital, and co-author of the study.

“Even though these patients have a high risk of bleeding complications, they also have a high risk of stroke, new myocardial infarction, and death,” says Spaak. “Thus, it is extra important to ensure a good therapy control—INR values in therapeutic range—in warfarin/coumarin patients with reduced kidney function.”

—Mark McGraw

Reference

Carrero J, Evans M, et al. Warfarin, Kidney Dysfunction, and Outcomes Following Acute Myocardial Infarction in Patients With Atrial Fibrillation. JAMA. 2014.