OASIS-2 (substudy)

Organization to Assess Strategies for Ischemic Syndromes – 2 (2001)

Condition

Anticoagulation in unstable angina

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Objective

To evaluate whether oral anticoagulant therapy given for 5 months was superior to standard therapy in patients with unstable angina receiving ASA

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Trial design

Randomized, controlled, double-blind study
Active treatment: oral anticoagulant therapy (loading dose of 10 mg followed by 3 mg once daily for 2 days, then target INR 2.5) in addition to ASA for 5 months (n=1848)
Control treatment: standard therapy with ASA alone for 5 months (n=1864)

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Endpoints

Primary efficacy endpoint: composite of cardiovascular death, myocardial infarction, or stroke
Secondary efficacy endpoints: composite of cardiovascular death, myocardial infarction, stroke and readmission to the hospital for unstable angina
Safety endpoints: major and minor bleeding

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Trial participants

3.712 patients eligible for the main OASIS-2 trial, which compared a 3-day regimen of hirudin vs. heparin, who could be randomized within 12 hours of symptom onset

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Results

Primary outcome: A primary endpoint occurred in 140 of 1848 patients (7.6%) randomized to oral anticoagulants compared to 155 patients (8.3%) in the control group (relative risk reduction 10%). 308 patients (16.7%) experienced the secondary outcome in the oral anticoagulant group compared to 327 patients (17.5%) in the control group (relative risk reduction 5%)
Safety outcome: Major bleeding occurred in 49 patients (2.7%) in the oral anticoagulant group compared to 25 control patients (1.3%). Life-threatening bleedings accounted for about half of these events

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Summary

Efficacy: In the group receiving oral anticoagulants, a small, non-significant reduction in the risk of the primary (cardiovascular death, myocardial infarction, stroke) and secondary (cardiovascular death, myocardial infarction, stroke, readmission to hospital for unstable angina) efficacy outcomes was observed
Safety: There was an excess of major and minor bleeding with oral anticoagulants

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Reference

Yusuf S, Pogue J, Anand S for the OASIS Investigators. Effects of long-term, moderate-intensity oral anticoagulation in addition to aspirin in unstable angina. J Am Coll Cardiol 2001;37:475-484

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Corresponding author

Salim Yusuf, MD, Canadian Cardiovascular Collaboration Project Office, Hamilton General Hospital, McMaster Clinic, Room 252, 237 Barton Street East, Hamilton, Ontario L8L 2X2 Canada, e-mail: yusufs@mcmaster.ca

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