[Prospective 12-year follow-up study of clinical and hemodynamic sequelae of deep venous thromboses in patients with low risk (Zurich Study)].

No prospective study of the long-term sequelae of more than 10 years after acute deep vein thrombosis exists so far. Therefore, 28 patients with DVT were included in a prospective study to evaluate the natural history of postthrombotic syndrome. Clinical and hemodynamic examinations were performed at the time of admission; after 3, 6 and 12 months; after the 2nd, 3rd, 4th, 5th; and finally after the 12th year. All patients received unfractionated heparin initially and oral anticoagulants subsequently. After 12 years, 64% of the patients exhibited normal findings. Mild skin changes were found in 28%, marked trophic changes in 5%, and only 1 venous ulcer occurred. Regular use of compression stockings was reported by 54% of the patients with multilevel disease. Although mean maximum venous outflow was significantly reduced from the acute event to 2 years later (p < 0.003) compared with the contralateral leg, a significant (p < 0.05) improvement was observed 6 months later. Recanalization of calf vein thrombosis was detected by Doppler sonography after 3 months. 64% of the multilevel thromboses were recanalized completely or in part after 1 year; in 69%, valvular incompetence was found. In conclusion, in contrast to earlier reports, this prospective study up to 12 years after DVT demonstrates a low incidence of PTS by administration of initially unfractionated heparin, oral anticoagulation and compression therapy. However, the adverse clinical event rate (mortality 14%) and recurrency rate of 24% show that the prognosis after DVT does not appear favorable even in low-risk patients.