The benefits of anticoagulation with warfarin outweigh the risks in patients with chronic kidney disease, even for those with the most severe kidney damage, a Swedish study has found.
The study – published in this week’s JAMA – showed warfarin treatment reduced the risk of thrombotic events in post-MI patients with atrial fibrillation and chronic kidney disease (CKD), without increasing their risk of bleeding.
International kidney disease guidelines were recently modified to advise caution over warfarin use in patients with CKD because of their increased bleeding risk, while NICE continues to note that little is known about the benefits versus risks of treatment in patients with CKD in draft updated atrial fibrillation guidance published earlier this year.
The Swedish study, based on national registry data, included 24,317 patients who survived an MI and had atrial fibrillation, 5,292 (21.8%) of whom were treated with warfarin at discharge from hospital and 12,583 (51.7%) of whom had CKD stage 3 or worse.
Over 12 months of follow-up, the patients treated with warfarin had an 18% lower relative risk of recurrent MI, stroke or death than untreated patients, but the same risk of haemorrhage.
The pattern was the same among those patients with CKD and across different levels of severity of CKD. Warfarin treatment resulted in 18%, 17%, 13% and 20% reductions in the risk of recurrent MI, stroke or death among patients with eGFR > 60, >30-60, >15-30 and <15, ml/min per 1.73 m2, respectively, without an increase in bleeding risk.
The authors, led by a team at the Karolinska Institute in Stockholm, concluded: ‘Warfarin treatment was associated with a lower one-year risk for the composite outcome of death, MI, and ischemic stroke without a higher risk of bleeding in consecutive acute MI patients with atrial fibrillation. This association was not related to the severity of concurrent CKD.’
An editorial in the same issue of the journal cautioned that the findings may not apply to treatment of all patients with atrial fibrillation in settings other than following MI – and stressed time in therapeutic range remains the most important guide to warfarin’s effectiveness and safety.
The authors wrote: ‘These data support the use and continuation of warfarin therapy among patients with CKD with excellent INR control.’
JAMA 2014; available online 5 March
