Residual vein thrombosis and trans-popliteal reflux in patients with and without the post-thrombotic syndrome.

doi: 10.1160/TH13-06-0442 Thromb Haemost 2013; 110: 854–855 Dear Sirs, Post-thrombotic manifestations develop in up to 50% of patients with proximal deepvein thrombosis (DVT) of the lower extremities as a result of venous hypertension (1). Whether the post-thrombotic syndrome (PTS) is predominantly the consequence of outflow obstruction, venous valvular reflux or both is conflicting (2-5). With a prospective cohort design we assessed the development of residual vein thrombosis (RVT) and popliteal valve incompetence (PVI) in 290 consecutive patients with the first episode of proximal DVT who received conventional anticoagulation, were instructed to wear compression elastic stockings for at least two years, and were followed-up for up to three years. The development of post-thrombotic signs and symptoms was assessed at predefined times along the three-year follow-up using the Villalta scale (1). Briefly, the presence of five leg symptoms (i.e. pain, cramps, heaviness, pruritus, and paresthesia) and six objective signs (i.e. pretibial oedema, induration of the skin, hyperpigmentation, new venous ectasia, redness and pain during calf compression) was scored. For each item, a score of 0 up to 3 was assigned using the contralateral unaffected leg as denominator for all evaluations. The presence of a venous ulcer of the lower limb indicated severe PTS. In the absence of a venous ulcer, patients were classified as having severe PTS if they had a score of 15 or more on two consecutive visits, at least three months apart. A total score of 5 to 14 on two consecutive visits, at least three months apart, indicated mild PTS. The investigation was approved by the Ethical Board of our Institution, and all patients gave their written informed consent for participation in the study. Three and six months after the index DVT, the patients received the ultrasound assessment of the common femoral and the popliteal vein to determine the presence of RVT, and the colour-Doppler assessment of the popliteal vein to determine the development of PVI. Veins were considered as recanalised in case of a vein diameter under maximum compressibility < 4 mm within six months of the DVT diagnosis. The presence in at least one examination of a retrograde flow through the popliteal valve after a standardised compression of the midthigh, persisting after repeating the maneuver with a tourniquet to prevent the influence of superficial vein reflux, was considered suggestive of valve incompetence. An incompetent vein was defined by an abnormal valve closure time that produced a greater than 0.5 seconds reversal flow. For the comparison between the baseline characteristics of patients who developed the PTS and those who did not, we performed the t-test for continuous variables and the chi-square test for categorical variables. A p-value < 0.05 was regarded as statistically significant. For the assessment of the risk of PTS conferred by RVT and/or PVI, we calculated the relative risk (RR) after adjusting it for age and sex. PTS developed in 119 patients (41.0%; 95% confidence interval [CI], 35.4 to 46.7) and was severe in six. The main baseline