Spontaneous recanalization in deep venous thrombosis: a prospective duplex ultrasound study.

Aim: The aim of this study was to evaluate the dynamics of the recanalization process (spontaneous fibrinolysis) in completely occlusive deep venous thrombosis (DVT) using duplex ultrasound examination and to investigate the influence of different factors on the evolution of thrombus regression.

Methods: This longitudinal prospective study was done with 74 consecutive patients with completely occlusive acute multilevel DVT, confirmed by echo duplex scan after 1, 3, 6, and 12 months. At each re-evaluation, the degree and the type of recanalization were determined. Efficacy of tinzaparin (175 IU/kg, s.c., q.d. for 7-14 days) and continued with warfarin (12 months at INR 2-3) as well as patients' compliance with compressive elastic hosiery wearing were carefully followed. Relationship between the degree and pattern of recanalization and patients' age, gender, as well as thrombosis etiology and location were determined.

Results: Sixty-four patients completed the study. The mean recanalization rate was 39.7% at 1, 64.8% at 3, 82% at 6, and 90.3% at 12 months. Marginal recanalization was more frequently observed, but recanalization pattern was changing during follow-up.

Conclusions: In the case of efficient anticoagulant and compressive therapy, the spontaneous recanalization process of DVT is important from the very first month of evolution, but an almost complete re-permeabilization is observed only after 12 months of treatment. The unilocular, marginal pattern of thrombus lysis is often observed and has better evolution than the multilocular cavernous one. The dynamics of recanalization are characterized by distal-to-proximal extension and in the first 6 months are significantly influenced by patient's gender and thrombosis etiology.