Prolonged Anticoagulation After a First Episod of Idiopathic Proximal Deep Vein Thrombosis (PADIS TVP)

Inclusion Criteria: * Patients with a first episode of idiopathic proximal deep vein thrombosis who have been treated during 6 months (Plus or minus 15 days) using Vitamin K antagonist with a INR between 2 and 3. Exclusion Criteria: * Age \> 18 * warfarin hypersensibility * unwilling or unable to give writting informed consent * distal deep vein thrombosis or pulmonary embolism * Proximal deep vein thrombosis which was provoked by a reversible major risk factor * major thrombophilia (protein C, S or antithrombin deficiency, antiphospholipids antibodies, homozygous factor V Leiden) * previous documented episode of proximale deep vein thrombosis or pulmonary embolism * other indication for anticoagulant therapy (e.g.:atrial fibrillation, mechanic valve) * patient on antithrombotic agent in whom antithrombotic agent should be started again after stopping anticoagulation * pregnancy * women without contraception * planned major surgery in the next 18 months * ongoing cancer or cured cancer in less than 2 years * serious bleeding risk (e.g.: gastric ulcer) * platelet count less than 100 Giga/l * Life expectancy less than 18 months