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Published on: February 28, 2012
Apixaban for Stroke Prevention in Subclinical Atrial Fibrillation
Jeff S Healey1, Renato D Lopes1, Christopher B Granger1
1From the Population Health Research Institute, McMaster University, Hamilton, ON (J.S.H., W.F.M., D.C., J.A.W., L.X., K.S., S.N., R.M., S.J.C.), the Montreal Heart Institute, University of Montreal, Montreal (L.R.), the University of Ottawa Heart Institute, Ottawa (D.H.B.), Institut Universitaire de Cardiologie et de Pneumologie de Québec, Laval University, Quebec, QC (F.P.), the Department of Clinical Neurosciences, Radiology, and Community Health Sciences, Hotchkiss Brain Institute, University of Calgary, Calgary, AB (S.B.C.), and the Université de Sherbrooke, Sherbrooke, QC (F.A.-P.) - all in Canada; the Duke Clinical Research Institute, Duke University, Durham, NC (R.D.L., C.B.G.); Amphia Ziekenhuis, Breda, the Netherlands (M.A.); Oslo University Hospital and the University of Oslo, Oslo (D.A.); the University of Modena and Reggio Emilia, Modena (G.B.), and the Department of Clinical Sciences and Community Health, University of Milan, and the Division of Subacute Care, IRCCS Istituti Clinici Scientifici Maugeri, Milan (M. Proietti) - all in Italy; St. George's, University of London, London (A.J.C.), and Liverpool Heart and Chest Hospital, Liverpool (D.J.W.) - both in the United Kingdom; J.W. Goethe University, University Hospital Department of Cardiology, Frankfurt, Germany (J.W.E., S.H.H.); the Medical University of South Carolina, Charleston (M.R.G.); Michigan State University, Lansing (J.I.); the Institute for Clinical and Experimental Medicine, Prague, Czech Republic (J.K.); the University of Rochester, Rochester, NY (V.K.); Semmelweis University, Budapest, Hungary (V.K.); Karolinska Institutet and the Heart, Vascular, and Neurology Theme, Karolinska University Hospital, Stockholm (C.L.); the University of Rennes, Rennes, France (P.M.); Cliniques du Sud-Luxembourg, Arlon, Belgium (G.M.); Hospital Universitario La Luz, Madrid (J.B.M.), and Hospital Costa del Sol, Marbella (M. Pombo) - both in Spain; Aarhus University Hospital and Aarhus University, Aarhus, Denmark (J.C.N.); University Hospital Basel, University of Basel, Basel, Switzerland (C.S.); the Veterans Affairs Portland Health Care System, Portland, OR (I.G.Z.); and Abrazo Arrowhead Hospital, Glendale, AZ (A.K.).
Background:
Subclinical atrial fibrillation is short-lasting and asymptomatic and can usually be detected only by long-term continuous monitoring with pacemakers or defibrillators. Subclinical atrial fibrillation is associated with an increased risk of stroke by a factor of 2.5; however, treatment with oral anticoagulation is of uncertain benefit.
Methods:
We conducted a trial involving patients with subclinical atrial fibrillation lasting 6 minutes to 24 hours. Patients were randomly assigned in a double-blind, double-dummy design to receive apixaban at a dose of 5 mg twice daily (2.5 mg twice daily when indicated) or aspirin at a dose of 81 mg daily. The trial medication was discontinued and anticoagulation started if subclinical atrial fibrillation lasting more than 24 hours or clinical atrial fibrillation developed. The primary efficacy outcome, stroke or systemic embolism, was assessed in the intention-to-treat population (all the patients who had undergone randomization); the primary safety outcome, major bleeding, was assessed in the on-treatment population (all the patients who had undergone randomization and received at least one dose of the assigned trial drug, with follow-up censored 5 days after permanent discontinuation of trial medication for any reason).
Results:
We included 4012 patients with a mean (±SD) age of 76.8±7.6 years and a mean CHA2DS2-VASc score of 3.9±1.1 (scores range from 0 to 9, with higher scores indicating a higher risk of stroke); 36.1% of the patients were women. After a mean follow-up of 3.5±1.8 years, stroke or systemic embolism occurred in 55 patients in the apixaban group (0.78% per patient-year) and in 86 patients in the aspirin group (1.24% per patient-year) (hazard ratio, 0.63; 95% confidence interval [CI], 0.45 to 0.88; P = 0.007). In the on-treatment population, the rate of major bleeding was 1.71% per patient-year in the apixaban group and 0.94% per patient-year in the aspirin group (hazard ratio, 1.80; 95% CI, 1.26 to 2.57; P = 0.001). Fatal bleeding occurred in 5 patients in the apixaban group and 8 patients in the aspirin group.
Conclusions:
Among patients with subclinical atrial fibrillation, apixaban resulted in a lower risk of stroke or systemic embolism than aspirin but a higher risk of major bleeding. (Funded by the Canadian Institutes of Health Research and others; ARTESIA ClinicalTrials.gov number, NCT01938248.).
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