Aspirin did not significantly reduce the rate of recurrent venous thromboembolism compared to placebo (4.8% vs 6.5% per year; HR 0.74; 95% CI 0.52-1.05; P=0.09).
RCT (n=822)
Does aspirin 100 mg daily reduce the recurrence of venous thromboembolism in patients who have completed initial anticoagulant therapy after a first episode of unprovoked venous thromboembolism?
Low-dose aspirin after initial anticoagulation for unprovoked VTE did not significantly reduce VTE recurrence but significantly reduced major vascular events without increasing bleeding risk.
Effect estimate: HR 0.74 (95% CI 0.52-1.05)
Absolute Event Rate: 4.8% vs 6.5%
p-value: p=0.09
BACKGROUND: Patients who have had a first episode of unprovoked venous thromboembolism have a high risk of recurrence after anticoagulants are discontinued. Aspirin may be effective in preventing a recurrence of venous thromboembolism. METHODS: We randomly assigned 822 patients who had completed initial anticoagulant therapy after a first episode of unprovoked venous thromboembolism to receive aspirin, at a dose of 100 mg daily, or placebo for up to 4 years. The primary outcome was a recurrence of venous thromboembolism. RESULTS: During a median follow-up period of 37.2 months, venous thromboembolism recurred in 73 of 411 patients assigned to placebo and in 57 of 411 assigned to aspirin (a rate of 6.5% per year vs. 4.8% per year; hazard ratio with aspirin, 0.74; 95% confidence interval CI, 0.52 to 1.05; P=0.09). Aspirin reduced the rate of the two prespecified secondary composite outcomes: the rate of venous thromboembolism, myocardial infarction, stroke, or cardiovascular death was reduced by 34% (a rate of 8.0% per year with placebo vs. 5.2% per year with aspirin; hazard ratio with aspirin, 0.66; 95% CI, 0.48 to 0.92; P=0.01), and the rate of venous thromboembolism, myocardial infarction, stroke, major bleeding, or death from any cause was reduced by 33% (hazard ratio, 0.67; 95% CI, 0.49 to 0.91; P=0.01). There was no significant between-group difference in the rates of major or clinically relevant nonmajor bleeding episodes (rate of 0.6% per year with placebo vs. 1.1% per year with aspirin, P=0.22) or serious adverse events. CONCLUSIONS: In this study, aspirin, as compared with placebo, did not significantly reduce the rate of recurrence of venous thromboembolism but resulted in a significant reduction in the rate of major vascular events, with improved net clinical benefit. These results substantiate earlier evidence of a therapeutic benefit of aspirin when it is given to patients after initial anticoagulant therapy for a first episode of unprovoked venous thromboembolism. (Funded by National Health and Medical Research Council Australia and others; Australian New Zealand Clinical Trials Registry number, ACTRN12605000004662.).
Brighton et al. (Sun,) conducted a rct in First episode of unprovoked venous thromboembolism (n=822). Aspirin vs. Placebo was evaluated on Recurrence of venous thromboembolism (HR 0.74, 95% CI 0.52-1.05, p=0.09). Aspirin did not significantly reduce the rate of recurrent venous thromboembolism compared to placebo (4.8% vs 6.5% per year; HR 0.74; 95% CI 0.52-1.05; P=0.09).