Net Clinical Benefit of Warfarin in Patients with Atrial Fibrillation: A Report from the Swedish Atrial Fibrillation Cohort Study
Background—Known risk factors for bleeding during anticoagulant treatment are largely the same as those predicting thromboembolic events in patients with atrial fibrillation (AF). Our objective was to investigate how to maximize the likelihood of avoiding both stroke and bleeding.
Methods and Results—All 182,678 subjects with AF in the Swedish Hospital Discharge Register were studied for an average of 1.5 years (260,000 patient-years at risk). Patients were stratified according to risk scores using historic ICD-diagnostic codes in the register. Information about medication was obtained from the Swedish Drug Registry. Our primary endpoint was net benefit defined as number of avoided ischaemic strokes with anticoagulation minus number of excess intracranial bleedings with a weight of 1.5 to compensate for the generally more severe outcome with intracranial bleedings. The adjusted net clinical benefit favoured anticoagulation for almost all AF patients. The exception were patients at very low risk of ischaemic stroke with a CHA2DS2-VASc score =0 and moderately elevated bleeding risk (-1.7%/year). The results were broadly similar with CHADS2, except for patients with very low embolic risk, where the CHA2DS2-VASc was able to identify those patients (n=6,205; 3.9% of all patients) who had no net clinical benefit or even some disadvantage from anticoagulant treatment.
Conclusions—In almost all patients with AF, the risk of ischaemic stroke without anticoagulant treatment is higher than the risk of intracranial bleeding with anticoagulant treatment. Analysis of the net benefit indicates that more patients may benefit from anticoagulant treatment.
- Received August 8, 2011.
- Accepted February 27, 2012.
- Copyright © 2012, American Heart Association, Inc. All rights reserved. Unauthorized use prohibited