Credit: Sage Ross
Low-dose aspirin can decrease the risk of major vascular events among patients with venous thromboembolism (VTE), according to a study published in Circulation.
The study included more than 1000 patients who had completed initial anticoagulant therapy after their first VTE.
Patients who went on to receive a daily dose of aspirin had a lower incidence of recurrent VTE, myocardial infarction, stroke, and cardiovascular death, compared
to those who received placebo.
The effects were not as substantial as those typically observed with warfarin or newer anticoagulants, but the results suggest low-dose aspirin is a feasible option for patients who cannot receive long-term anticoagulant therapy.
“The study provides evidence that, after a first venous thrombosis or embolism, daily aspirin reduces the risk of another event, without causing undue bleeding,” said study author John Simes, MD, of the University of Sydney in New South Wales, Australia.
“This treatment is an alternative to long-term anticoagulation and will be especially useful for patients who do not want the inconvenience of close medical monitoring or the risk of bleeding. [Additionally,] aspirin will be ideal in the many countries where prolonged anticoagulant treatment is too expensive.”
For this study, Dr Simes and his colleagues evaluated data from the ASPIRE and WARFASA trials. ASPIRE included 822 patients who were followed for an average of 3 years. And WARFASA included 402 patients who were followed for at least 2 years.
The patients had completed initial treatment with heparin and warfarin or an equivalent anticoagulant regimen following a first, unprovoked VTE. They were randomized to receive placebo (n=608) or a 100 mg daily dose of aspirin (n=616).
The researchers evaluated the differences between these 2 groups with regard to bleeding, recurrent VTE, and major vascular events, which includes recurrent VTE, myocardial infarction, stroke, and cardiovascular death.
VTE recurred in 18.4% of patients in the placebo arm and 13.1% of patients in the aspirin arm. The annual rate of recurrent VTE was 7.5% and 5.1%, respectively. So aspirin reduced the risk of VTE by 32% (hazard ratio [HR]=0.68, P=0.008).
Aspirin reduced the risk of deep vein thrombosis by 34% (HR=0.66, P=0.01) and the risk of pulmonary embolism by 34% (HR=0.66, P=0.08).
Aspirin also reduce the risk of major vascular events by 34%. The annual rate of these events was 5.7% in the aspirin arm and 8.7% in the placebo arm (HR=0.66, P=0.002).
There was no significant difference between the treatment arms with regard to bleeding. The annual rate of bleeding was 0.7% in the placebo arm and 1.1% in the aspirin arm. The annual rate of major bleeding was 0.4% and 0.5%, respectively.
“Aspirin does not require laboratory monitoring and is associated with about a 10-fold lower incidence of bleeding compared with oral anticoagulants,” said study author Cecilia Becattini, MD, of the University of Perugia in Italy.
“We are convinced that it will be an alternative for extended prevention of venous thromboembolism after 6 to 12 months of anticoagulant treatment.”
The researchers stressed that aspirin will not be a substitute for anticoagulant therapy in all patients. But it is an option for patients who are stopping anticoagulant therapy or for patients in whom long-term anticoagulant therapy is unsuitable.
“Although less effective, aspirin is inexpensive, easily obtainable, safe, and familiar to patients and clinicians worldwide,” Dr Simes noted. “If cost is the main consideration, aspirin is a particularly useful therapy. The costs of treating future thromboembolic events is greater than the cost of the preventive treatment.”
