CELEST trial is a controlled, randomized, multicentre, non-inferiority double-blind trial which aims to determine whether ECS applying 25mmHg of targeted pressure at the ankle are non inferior to ECS applying 35mmHg of targeted pressure at the ankle. Patients with a first acute symptomatic proximal DVT will be randomized to wear for two years either ECS applying 25mmHg of targeted pressure at the ankle or ECS applying 35mmHg of targeted pressure at the ankle. All patients will be prescribed anticoagulants for at least three months. The primary outcome will be the rate of PTS assessed with the Villalta scale in both arms of the study during the 2 years study period. Rate of compliance,severity of PTS and quality of life in both groups will constitute the main secondary outcomes.