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Second Copenhagen Atrial Fibrillation, Aspirin, and Anticoagulation Study - AFASAK-2
Description:
Warfarin, aspirin, or both for thromboembolic events in atrial fibrillation.
Hypothesis:
To compare the effects of fixed doses of warfarin and aspirin, separately and in combination, with the effects of adjusted-dose warfarin on preventing stroke in patients with chronic atrial fibrillation.
Study Design
Study Design:
Patients Screened: Not given
Patients Enrolled: 677
Mean Follow Up: 3 years
Mean Patient Age: 74
Patient Populations:
Chronic atrial fibrillation
Primary Endpoints:
Thromboembolic event (Stroke or systemic embolism)
Secondary Endpoints:
AMI, TIA, or death.
Major Bleeding requiring hospital intervention, involving CNS, or leading to permanent functional impairment or death.
Drug/Procedures Used:
Warfarin 1.25 mg qd; warfarin 1.25 mg qd with aspirin 300 mg qd, and aspirin 300 mg qd with warfarin adjusted to INR 2.0-3.0.
Principal Findings:
Patients with chronic atrial fibrillation were randomized into four groups. One group (167 patients) received fixed-dose warfarin (1.25 mg./day). The second group (171 patients) received 1.25 mg. of warfarin and 300 mg. of aspirin, and the third group (169 patients) received 300 mg. of aspirin. The fourth group (170 patients) received adjusted-dose warfarin (INR 2-3). Cumulative event rates were calculated by the Kaplan-Meier method.
During the study period, 58 patients dropped out, and 112 patients were withdrawn. There were 39 primary events and 47 secondary events. At the time that the study was terminated, 421 patients were on treatment and free of events.
After one year the primary event rate was 5.8% for patients on fixed-dose warfarin, 7.2% for patients on warfarin and aspirin, 3.6% on aspirin alone, and 2.8% on adjusted-dose warfarin. After three years the event rates were 11.9%, 12.8%, 8.4%, and 8.3%, respectively (p=0.67).
Major bleeding was rare with no difference detected among the four groups.
Increasing age, prior AMI, and adverse events during treatment were independent risk factors for primary events.
Interpretation:
Although there was no statistically significant difference in the rates of primary, secondary, and major hemorrhagic events between the groups, the statistical power of the study was limited due to its premature termination. Adjusted-dose warfarin appeared to have the lowest primary event rate. This study does not justify a change in the current recommendation of adjusted-dose warfarin INR 2-3 for stroke prevention in patients with atrial fibrillation.
References:
1. Eur Heart J 1998; 19(Abstr Suppl):154 Preliminary results
Keywords: Stroke, Platelet Aggregation Inhibitors, Warfarin, Risk Factors, Embolism, Hemorrhage
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