Elastic Compression Stockings for Prevention of Post-thrombotic Syndrome

superiority of targeted pressure at 35 mm Hg for compliant patients. Analysis of the primary endpoint per protocol amongst patients responding to the definition of compliance for compression scheduled by randomization

analysis of primary endpoint (cumulative incidence of PTS) amongst patients responding to the definition of observance for compression scheduled by randomization. It means a per protocol analysis. The per protocol analysis defined as follow : patients ideally compliant (see next secondary outcome measure with self declaration of compression carrying superior or equal to 80 % especially)and patients with respect to randomization.

Time frame: 24 months

Superiority of 25 mm Hg on the therapeutic compliance criterion

Superiority of 25 mm Hg on the therapeutic compliance criterion at 24 months Compliance is defined by 2 conditions : 1. Girerd adapted to elastic compression stocking score adjusted between 0 and 2 (the question 2 will not be taken into account beacause not adapted to the logistics of the study) 2. because of French clinical practices it should be pertinent to take into consideration 2 compliance type : 1. ideal compliance : Self declaration ≥ 80 % (reference PRANDONI) 2. adequate compliance : self declaration between 50 and 79% for (French references Delluc and Optimev study)

Time frame: 24 months

superiority of 25 mm Hg for constraints related to compression and chronic venous insufficiency quality of life (CIVIQ)

CIVIQ quality of life (CIVIQ 20) specific to chronic venous insufficiency at 3 months, 12 months and 24 months and questionnaire about constraints of compression stockings.

Time frame: 3 months, 12 months, 24 months

non inferiority of 25 mm Hg for the comparative evaluation of the symptomatic effect of short-term compression (pain, sensation of oedema) form baseline to 3 months

Comparison of evolution at short-term (3 months) of venous thrombosis symptoms (pain, oedema feeling). Self assessment by VAS of pain and oedema feeling once a week during 3 months. Assessment by the investigator at inclusion and during visit at 3 months (ankle measurement, clinical signs) will be done also. A statistical analysis will be done as soon as 3 months follow up data will be verified to evaluate symptoms evolution due to deep venous thrombosis.

Time frame: 3 months

Non-inferiority of 25 mm Hg for changes in overall quality of life evaluated on the basis of the EUROQUOL questionnaire

Non-inferiority of 25 mm Hg for changes in overall quality of life evaluated on the basis of the EUROQUOL questionnaire (EQ5D)

Time frame: 3months, 12 months, 24 months

non inferiority of 25 mm Hg for the intensity of long term chronic venous insufficiency symptoms (12 months and 24 months)

Long term assessment of evolution and intensity of symptoms (pain, oedema feeling) related to potential post-thrombotic syndrome apparition * Monthly self-assessment by VAS for pain and oedema feeling during 24 months. It will be done at the end of each month and will focus on symptoms intensity (last week of the month) * An assessment will be done by investigator, in addition of previous criterion, at 12 and 24 months * Assessment with the Ginsberg score (interview by the investigator at 12 and 24 months) * Comparison of averages on Villalta score (quantitative)

Time frame: 12 and 24 months

non inferiority of 25 mm Hg for the onset of permanent trophic disorders

CEAP classification evaluated by investigator at 3, 12 and 24 months

Time frame: 3 months, 12 and 24 months

non inferiority of 25 mm Hg for the onset of sequalae or post thrombotic residues on an duplex scan at 3 months, 12 and 24 months

Assessment by duplex scan of deep and superficial veins at 3, 12 and 24 months * Assessment by duplex scan of deep reflux (\>1s in femoral vein, and/or popliteal vein, tibio peroneal trunck) * Assessment by duplex scan of superficial reflux (\> 0.5s in great saphenous vein, small saphenous vein, perforating veins) * Assessment by echographic score of thickness and location of residual thrombus * Assessment by duplex scan of re-canalization of collectors trunks and/or parietal sequalae

Time frame: 3, 12 and 24 months

testing for the prognostic factors of the onset post thrombotic syndrome and comparison of the onset kinetics of post thrombotic syndrome

variables tested as prognostic factors of post thrombotic syndrome apparition : * location of the upper pole of thrombus * kinetic of thrombus lysis by duplex scan at 3 months * Idiopathic nature of TED * Delay of diagnostic of deep venous thrombosis * Initial intensity of deep venous thrombosis symptoms * Initial evolution of symptoms of deep venous thrombosis between J0 and 3 months * Persistence of the symptoms at 3 months * Patient's characteristics * Kinetic of of Villalta score apparition ≥ 5 by survival curve * Kinetic of post thrombotic syndrome apparition by Villalta score

Time frame: 24 months

test for key factors in good compliance

Compliance evaluation according to the 2 axes defined on third outcome measure and research of determinants of good compliance by specific questionnaire

Time frame: 24 months

Adverse events

description and comparison of the incidence of adverse events including unexpected adverse events, events expected with this type of disease (recurrence of the venous thromboembolic disease, recurrence of deep vein thrombosis, pulmonary embolism, superficial venous thrombosis, venous ulcer) and events possibly related to the study treatment (arterial decompensation passing to Lerich stage III or IV, skin intolerance)

Time frame: 24 months

Subgroups analysis of the primary objective and secondary objectives according to the gender stratification criterion and age

Stratification on age (more or less than 65 years-old) for testing the hypothesis by subgroups analysis of the benefit of a better adaptation of compression 25 mm Hg on older subjects, as suggested by S. Khan.

Time frame: 24 months

superiority of 25 mmHg on 35 mmHg in preventing the onset of clinical post thrombotic syndrome

superiority of 25 mmHg on 35 mmHg in preventing the onset of clinical post thrombotic syndrome. Outcome measure identical to primary endpoint

Time frame: 24 months

sensitivity analysis of primary endpoint excluding patients with a differential diagnosis can explain a Villalta score ≥ 5

sensitivity analysis of primary endpoint excluding patients with a differential diagnosis which could explain a Villalta score ≥ 5. Outcome measure identical to primary endpoint

Time frame: 24 months