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Warfarin confers a net clinical benefit for nearly all AF patients

NEW YORK (Reuters Health) – For all but a few patients with atrial fibrillation, the benefit of anticoagulation in preventing stroke outweighs the risk of intracranial bleeding, according to a Swedish study reported in Circulation online April 18.

“In short, when managing patients with AF, we essentially need to ask the question ‘who are the patients with bleeding risks that exceed the risk of ischemic stroke?’. Indeed, the present study only managed to identify a very small minority (consisting of 0.4% of all patients) where this was the case,” the authors wrote.

Dr. Leif Friberg, with the Karolinska Institute and Danderyd University Hospital in Stockholm, and colleagues point out that in patients with atrial fibrillation, risk factors for thromboembolic events are much the same as those for bleeding related to anticoagulant treatment. To determine which AF patients benefit on balance from anticoagulation, they examined data on 182,678 such patients in Sweden, where warfarin is the standard oral anticoagulant.

Subjects were followed for an average of 1.5 years and were stratified according to their risk for stroke and for bleeding based on standard algorithmic scores. Based on information from the national drug registry, 53% of the patients never used warfarin at any time.

The primary endpoint was net benefit of warfarin therapy, “defined as number of avoided ischemic 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 team explains.

Ischemic stroke rates increased from almost zero to 12% with increasing stroke-risk score in untreated patients, and up to 7% in warfarin-treated patients, according to the report. On the other hand, the annual rate of intracranial bleeding was 0.6 % in both warfarin-treated and untreated patients.

“The net result favored warfarin treatment for all patients, except for those at very low risk of ischemic stroke,” the authors report.

Patients with the highest risk scores for both stroke and for bleeding derived the highest net benefit (>6% per year), while only those with very low stroke risk and moderate bleeding risk had a net clinical disadvantage (-1.7% per year), the report indicates.

Dr. Friberg and colleagues conclude that more AF patients should be offered oral anticoagulant treatment. “An alternative and simpler approach to the anticoagulation issue could be to regard anticoagulation as the general rule for all AF patients, with exception for patients at very low risk of stroke,” they suggest.

SOURCE: http://bit.ly/JYIIy9

Circulation 2012.