Primary prevention of arterial thromboembolism in non-rheumatic atrial fibrillation in primary care: randomised controlled trial comparing two intensities of coumarin with aspirin

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Abstract
Objective: To investigate the effectiveness of aspirin and coumarin in preventing thromboembolism in patients with non-rheumatic atrial fibrillation in general practice. Design: Randomised controlled trial. Participants: 729 patients aged ≥60 years with atrial fibrillation, recruited in general practice, who had no established indication for coumarin. Mean age was 75 years and mean follow up 2.7 years. Setting: Primary care in the Netherlands. Interventions: Patients eligible for standard intensity coumarin (international normalised ratio 2.5-3.5) were randomly assigned to standard anticoagulation, very low intensity coumarin (international normalised ratio 1.1-1.6), or aspirin (150 mg/day) (stratum 1). Patients ineligible for standard anticoagulation were randomly assigned to low anticoagulation or aspirin (stratum 2). Main outcome measures: Stroke, systemic embolism, major haemorrhage, and vascular death. Results: 108 primary events occurred (annual event rate 5.5%), including 13 major haemorrhages (0.7% a year). The hazard ratio was 0.91 (0.61 to 1.36) for low anticoagulation versus aspirin and 0.78 (0.34 to 1.81) for standard anticoagulation versus aspirin. Non-vascular death was less common in the low anticoagulation group than in the aspirin group (0.41, 0.20 to 0.82). There was no significant difference between the treatment groups in bleeding incidence. High systolic and low diastolic blood pressure and age were independent prognostic factors. Conclusion: In a general practice population (without established indications for coumarin) neither low nor standard intensity anticoagulation is better than aspirin in preventing primary outcome events. Aspirin may therefore be the first choice in patients with atrial fibrillation in general practice. Studies have shown that patients with non-rheumatic atrial fibrillation may benefit from anticoagulation This study in a general practice population found no benefit of standard or low dose anticoagulation on risk of stroke, systemic embolism, major haemorrhage, or vascular death when compared with aspirin Hypertension and age were prognostic factors for event occurrence Aspirin is the treatment of choice for preventing thromboembolism in primary care patients at low risk