Aspirin to Prevent Recurrent Venous Thromboembolism - ASPIRE


The goal of the trial was to evaluate treatment with low-dose aspirin compared with placebo among patients with unprovoked venous thromboembolism who completed initial anticoagulation therapy.


Low-dose aspirin would prevent recurrent venous thromboembolism.

Study Design

  • Randomized
  • Blinded
  • Parallel
  • Placebo Controlled

Patient Populations:

  • Patients ≥18 years of age who had a first episode of unprovoked venous thromboembolism and completed initial anticoagulation therapy

    Number of enrollees: 822
    Duration of follow-up: Median 37 months
    Mean patient age: 55 years
    Percentage female: 45%


  • Venous thromboembolism had occurred >2 years prior to enrollment
  • Indication or contraindication to antiplatelet therapy
  • Indication for anticoagulation therapy
  • Limited life expectancy

Primary Endpoints:

  • Recurrence of venous thromboembolism; defined as symptomatic deep vein thrombosis, nonfatal pulmonary embolism, or fatal pulmonary embolism

Secondary Endpoints:

  • Venous thromboembolism, myocardial infarction, stroke, or cardiovascular death
  • Major bleeding and clinically relevant nonmajor bleeding

Drug/Procedures Used:

Patients who had a first episode of unprovoked venous thromboembolism and completed initial anticoagulation therapy were randomized to aspirin 100 mg daily (n = 411) versus placebo daily (n = 411).

The duration of initial anticoagulation therapy (6 weeks to 24 months) was selected by the treating physician.

Principal Findings:

Overall, 822 patients were randomized. The mean age was 55 years, 45% were women, and 39% had a body mass index ≥30 kg/m2. The duration of anticoagulation therapy prior to enrollment was 3-6 months in 28%, 6-12 months in 63%, and ≥12 months in 8%.

At a median follow-up of 37 months, the primary outcome of recurrent venous thromboembolism occurred in 14% of the aspirin group versus 18% of the placebo group (p = 0.09).

The following individual outcomes are reported as % per year for aspirin versus placebo groups:
- Major vascular events: 5.2% versus 8.0% (p = 0.01)
- Major bleeding and clinically relevant non-major bleeding: 1.1% versus 0.6% (p = 0.22)
- Major vascular event, major bleeding, or all-cause mortality: 6.0% versus 9.0% (p = 0.01)

Pooling the results of the ASPIRE and WARFASA trials, aspirin was associated with a 32% reduction in venous thromboembolism (p = 0.007), a 34% reduction in major vascular events (p = 0.002), with no increase in clinically relevant bleeding (p = 0.31).


Among patients with unprovoked first venous thromboembolism who completed initial anticoagulation therapy, the use of aspirin failed to reduce the primary outcome of recurrent venous thromboembolism. The ASPIRE trial had less power than originally planned due to slow enrollment. Combining the findings of ASPIRE with the similar patient population of the WARFASA trial demonstrated a modest reduction in recurrent venous thromboembolism from aspirin therapy. Patients who suffer a venous thromboembolism appear to be at risk of an arterial vascular event, of which low-dose aspirin therapy effectively prevented without increasing major bleeding.


Brighton TA, Eikelboom JW, Mann K, et al., on behalf of the ASPIRE Investigators. Low-dose aspirin for preventing recurrent venous thromboembolism. N Engl J Med 2012;Nov 4:[Epub ahead of print].

Presented by Dr. Timothy Brighton at the American Heart Association Scientific Sessions, Los Angeles, CA, November 4, 2012.

Clinical Topics: Anticoagulation Management, Pulmonary Hypertension and Venous Thromboembolism, Vascular Medicine, Anticoagulation Management and Venothromboembolism

Keywords: Follow-Up Studies, Body Mass Index, Warfarin, Venous Thromboembolism, Hemorrhage

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