Canadian Atrial Fibrillation Anticoagulation study (1991)


Prevention of stroke and systemic embolism in patients with non-valvular AF 

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To assess the potential of warfarin to to reduce systemic thromboembolism and its inherent risk of hemorrhage in patients with AF 

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Trial design

Randomized double-blind, placebo-controlled study
Active treatment: warfarin (INR 2.0–3.0) (n=187)
Control treatment: placebo (n=191)

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Primary endpoint: composite of non-lacunar stroke, non-CNS systemic embolism, and fatal or intracranial hemorrhage
Secondary endpoints: TIA, lacunar infarction, major bleeding, minor bleeding, and death

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Trial participants

378 patients (planned 630) with AF; mean age 67.7 years

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Efficacy outcome: Primary outcome events occurred in 7 of 187 patients receiving warfarin and in 11 of 191 patients receiving placebo corresponding to an annual rate of 3.5% and 5.2%, respectively (relative risk reduction 37%). The annual rate of the event cluster non-lacunar stroke or non-CNS embolic events was 2.5% with warfarin and 5.2% with placebo, the resulting relative risk reduction 55%. Recruitment and follow-up were stopped early because two other similar studies had shown a decrease in the rate of stroke among patients treated with warfarin.
Safety outcome: Fatal or major bleeding occurred in 5 patients receiving warfarin and one patient receiving placebo. The corresponding annual rates were 2.5% in warfarin-treated and 0.5% in placebo-treated patients. Minor bleeding occurred in 16% of patients receiving warfarin and 9.4% receiving placebo

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Efficacy: In AF-patients, anticoagulation with warfarin was superior to placebo in reducing non-lacunar stroke and non-CNS embolism
Safety: Major and minor bleedings were more common in the warfarin group

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Connolly SJ, Laupacis A, Gent M, Roberts RS, Cairns JA, Joyner C. Canadian Atrial Fibrillation Anticoagulation (CAFA) Study. J Am Coll Cardiol 1991;18:349-355

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Corresponding author

Stuart J. Connolly, MD, Population Health Research Institute, McMaster University, 237 Barton Street East, Hamilton, ON L8L 2X2, Canada

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