Net Clinical Benefit of Warfarin in Patients With Atrial Fibrillation: A Report From the Swedish Atrial Fibrillation Cohort Study
What is the risk:benefit ratio of warfarin in patients with atrial fibrillation (AF)?
The data in this study were obtained from a national database that included 170,292 patients (mean age 76 years) with a diagnosis of AF in 2005-2008. Fifty-three percent of patients were not treated with warfarin. The mean duration of follow-up was 1.5 years. Net clinical benefit (NCB) was defined as the number of ischemic strokes off warfarin minus the number of intracranial hemorrhages on warfarin with a weight of 1.5 to account for the more severe consequences of intracranial hemorrhage. NCBs were analyzed according to stroke risk (CHA2DS2-VASc score) and bleeding risk (HAS-BLED score).
The NCB favored warfarin for patients with a CHA2DS2-VASc score ≥1. The greatest NCB occurred in patients with the highest risk scores. The adjusted NCB was >6%/year in patients with a CHA2DS2-VASc score of 6 and a HAS-BLED score of 4. In the small subgroup of patients with a CHA2DS2-VASc score of 0 and moderately elevated bleeding risk, the NCB did not favor warfarin.
The authors concluded that the risk of ischemic stroke off warfarin exceeds the risk of intracranial hemorrhage on warfarin for almost all patients with AF.
Of note is that the risk of intracranial bleeding on warfarin exceeded the risk of ischemic stroke off warfarin in only 0.4% of patients in this very large AF cohort. The data indicate that almost all patients with AF have more to gain than to lose from anticoagulation with warfarin.
Keywords: Odds Ratio, Stroke, Intracranial Hemorrhages, Follow-Up Studies, Warfarin, Atrial Fibrillation, Risk Assessment
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