Published Online
on August 28, 2008

A more recent version of this article appeared on January 1, 2009

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Submitted on February 29, 2008
Revised on May 5, 2008
Accepted on May 20, 2008

Potentially Preventable Strokes in High-Risk Patients With Atrial Fibrillation Who Are Not Adequately Anticoagulated

David J. Gladstone MD, PhD^*; Esther Bui MD; Jiming Fang PhD; Andreas Laupacis MD; M. Patrice Lindsay MSc; Jack V. Tu MD, PhD; Frank L. Silver MD; and Moira K. Kapral MD, MSc

From the Institute for Clinical Evaluative Sciences (D.J.G., J.F., A.L., M.P.L., J.V.T., F.L.S., M.K.K.), Toronto, Canada; Division of Neurology (D.J.G., E.B., F.L.S.), Department of Medicine (D.J.G., J.V.T.), Regional Stroke Centre and Neurosciences Program (D.J.G.), Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Canada; Department of Medicine (A.L., J.V.T., F.L.S., M.K.K.), and the Department of Health Policy, Management and Evaluation (J.V.T., M.K.K.), University of Toronto, Toronto, Canada; the Division of General Internal Medicine and Clinical Epidemiology (M.K.K.), and the Women's Health Program (M.K.K.), University Health Network, Toronto, Canada; the Heart and Stroke Foundation Centre for Stroke Recovery (D.J.G.); the Keenan Research Centre at the Li Ka Shing Knowledge Institute of St. Michael's Hospital (A.L.), Toronto, Canada; and the Canadian Stroke Network (M.P.L., J.V.T., F.L.S., M.K.K.).

^* To whom correspondence should be addressed. E-mail: david.gladstone{at}sunnybrook.ca.

Background and Purpose—Warfarin is the most effective stroke prevention medication for high-risk individuals with atrial fibrillation, yet it is often underused. This study examined the magnitude of this problem in a large contemporary, prospective stroke registry.

Methods—We analyzed data from the Registry of the Canadian Stroke Network, a prospective database of consecutive patients with stroke admitted to 12 designated stroke centers in Ontario (2003 to 2007). We included patients admitted with an acute ischemic stroke who (1) had a known history of atrial fibrillation; (2) were classified as high risk for systemic emboli according to published guidelines; and (3) had no known contraindications to anticoagulation. Primary end points were the use of prestroke antithrombotic medications and admission international normalized ratio.

Results—Among patients admitted with a first ischemic stroke who had known atrial fibrillation (n=597), strokes were disabling in 60% and fatal in 20%. Preadmission medications were warfarin (40%), antiplatelet therapy (30%), and no antithrombotics (29%). Of those taking warfarin, three fourths had a subtherapeutic international normalized ratio (<2.0) at the time of stroke admission. Overall, only 10% of patients with acute stroke with known atrial fibrillation were therapeutically anticoagulated (international normalized ratio 2.0) at admission. In stroke patients with a history of atrial fibrillation and a previous transient ischemic attack or ischemic stroke (n=323), only 18% were taking warfarin with therapeutic international normalized ratio at the time of admission for stroke, 39% were taking warfarin with subtherapeutic international normalized ratio, and 15% were on no antithrombotic therapy.

Conclusions—In high-risk patients with atrial fibrillation admitted with a stroke, and who were candidates for anticoagulation, most were either not taking warfarin or were subtherapeutic at the time of ischemic stroke. Many were on no antithrombotic therapy. These findings should encourage greater efforts to prescribe and monitor appropriate antithrombotic therapy to prevent stroke in individuals with atrial fibrillation.

Key words: anticoagulation • aspirin • atrial fibrillation • prevention • stroke • warfarin

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Warfarin: An Inconvenient Truth

Melina Gattellari, John Worthington, and Nicholas Zwar
Stroke 2009 40: 5-7. [Extract] [Full Text] [PDF]

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