Aspirin for prevention and treatment of venous thromboembolism.

Venous and arterial thromboses have been regarded for many years as two different diseases requiring anticoagulant or antiplatelet treatment, respectively. Platelets have a role in venous thromboembolism through several mechanisms, including the formation of and adhesion to the neutrophil extracellular traps, as recently demonstrated. When given for antithrombotic prophylaxis in high risk medical or surgical patients, aspirin was shown to reduce the incidence of venous thromboembolism in clinical studies and meta-analyses. However, controversial recommendations have been released on the role of aspirin for the prevention of venous thromboembolism. Two randomized, double blind trials have recently shown a reduction of recurrence by about 30% with aspirin compared to placebo in patients who had completed treatment with vitamin K antagonists for a first episode of unprovoked venous thromboembolism. The clinical value of this risk reduction in comparison to that obtained with warfarin and the new oral anticoagulant agents, should take into account the low risk for bleeding and costs associated with aspirin. Given its safety, worldwide availability and low cost, aspirin can be considered a valid alternative to oral anticoagulants for the extended treatment of venous thromboembolism after a first unprovoked event.