Venous haemodynamics and morphology in relation to recanalisation and thrombus resolution in patients with proximal deep venous thrombosis

Objective: Follow-up studies of deep venous thrombosis (DVT) are needed to gain increased knowledge of the process of recanalisation over time. In thi s study modern diagnostic techniques were used to analyse changes in venous circulation during the process of recanalisation and thrombus resolution. Design and setting: Prospective follow-up study of patients with symptomati c DVT referred to a vascular diagnostic laboratory. The patients were evalu ated by repeated examinations with colour duplex ultrasound and computerise d strain-gauge plethysmography. Patients: Eighteen consecutive patients with acute DVT occluding the calf v eins and femoro-popliteal vein segments. Main outcome measures: Ultrasonographic assessment of thrombus resolution a nd flow patterns in deep and superficial veins. Plethysmographic determinat ion of venous volume and venous outflow capacity. Results: At 3 months' and 6 months' follow-up, 33% and 56%, respectively, w ere recanalised but almost all limbs still had some degree of functional ou tflow obstruction. Duplex evaluation further demonstrated a complex pattern of recanalisation with thrombus resolution from above, from below or both. Computerised strain-gauge plethysmography showed a progressive time-relate d increase in venous outflow capacity and venous volume over 6 months, but volumetric variables could not be used to distinguish between limbs with pa tent veins and those with still-occluded veins. None of the limbs had compl etely compressible femoro-popliteal venous segments at the end of the follo w-up. Conclusion: The combination of these two modern diagnostic techniques, suit able for repeated studies, can provide detailed information on morphologica l and haemodynamic changes occurring during the process of recanalisation a nd thrombus resolution.