The results of the Prolong study, currently submitted for publication, show that patients with a first unprovoked venous thromboembolic event who have altered D-dimer levels, measured one month after anticoagulation with vitamin K antagonists is stopped, have a high rate of recurrences (about 14%) and a prolongation of anticoagulation is effective in reducing significantly this rate. Those patients with normal D-dimer (about 60% of all patients examined) have a low rate of recurrences (about 5%) and likely a prolongation of anticoagulation in all these patients cannot be recommended.

In line with these results, the Prolong-Two study aims at assessing the predictive role for recurrence of D-dimer levels measured: a) during anticoagulation, b) one month after its withdrawal and c) periodically during follow up.

Patients with a first unprovoked venous thromboembolism (including proximal deep vein thrombosis of a leg and/or pulmonary embolism) which are treated with vitamin K antagonists for not less than 6 months are considered for the study. D-dimer assay is performed during anticoagulation and patients with altered results continue the anticoagulation for 6 more months. Those with normal D-dimer stop the anticoagulant treatment and are again examined one month later. Anticoagulation is resumed for 6 more months in those patients with abnormal D-dimer results but is permanently stopped in those with a normal assay. The latter patients are examined and D-dimer assay performed again every two months to evaluate the natural history of the assay after anticoagulation is stopped and the possible predictive value for recurrence of a change of the assay during follow-up from normal to abnormal results.

Inclusion Criteria

• Age > 18 years
• After a first documented idiopathic proximal deep vein thrombosis and/or pulmonary embolism
• After at least 6 months of oral anticoagulation
• After written informed consent

Exclusion Criteria:

• Age > 82 y
• Recurrent venous thromboembolism
• If the Venous thromboembolism occurred:
• during pregnancy or puerperium
• after recent (i.e. within three months) fracture or plaster casting of a leg,
• after immobilization with confinement to bed for three consecutive days after surgery with general anesthesia lasting longer than 30 minutes
• Patients with:
• active cancer
• antiphospholipid antibody syndrome
• antithrombin deficiency
• serious liver disease or renal insufficiency (creatininemia > 2 mg/dL),
• other indications for anticoagulation or contraindications for this treatment
• limited life expectation
• Patients who live too far from the clinical center

Subjects with a single previous idiopathic venous thromboembolic event who stop anticoagulation