"Aspirin for the Prevention of Recurrent Venous Thromboembolism". The New England Journal of Medicine. Published on November 4, 2012.

Clinical Question

Does aspirin reduce the recurrence of venous thromboembolism (VTE) in patients who have completed initial anticoagulant therapy after a first episode of unprovoked VTE?

Bottom Line

Major Points

Patients with a first episode of unprovoked VTE have a high risk of recurrence when anticoagulants are discontinued. Although aspirin is effective in preventing arterial thrombotic events and primary VTE in high-risk surgical patients, its efficacy in preventing recurrent VTE after the discontinuation of anticoagulants was uncertain.

Guidelines

At the time of publication and the conclusion of the study, guidelines reflecting these results were not specified.

Design

Population

Inclusion Criteria:
- At least 18 years of age
- Completed initial anticoagulation therapy (6 weeks to 24 months) after a first unprovoked episode of symptomatic deep-vein thrombosis or acute pulmonary embolism
Exclusion Criteria:
- VTE occurred more than 2 years before enrollment
- Patients with indications or contraindications to aspirin or other antiplatelet therapy, patients who required long-term anticoagulation, or those with other serious conditions

Interventions

- Aspirin 100 mg daily (n=411)
- Placebo (n=411)

Outcomes

Primary Outcome:
- Recurrence of VTE. The aspirin group showed a 26% risk reduction compared to placebo, but this was not statistically significant (hazard ratio with aspirin, 0.74; 95% CI, 0.52 to 1.05; P=0.09).

Secondary Outcomes:
- Major vascular events defined as a composite of VTE, MI, stroke, or cardiovascular death were reduced by 34% in the aspirin group compared to placebo (hazard ratio with aspirin, 0.66; 95% CI, 0.48 to 0.92; P=0.01).

Criticisms

- The study did not reach the initial recruitment goal, resulting in limited power to detect a significant reduction in the primary outcome.
- High rate of discontinuation of the study drug may have underestimated the benefits of aspirin therapy.

Funding

Funded by National Health and Medical Research Council (Australia), Health Research Council (New Zealand), Australasian Society of Thrombosis and Hemostasis, National Heart Foundation of Australia, and Bayer HealthCare.

Further Reading