THE ROLE OF VENOUS OUTFLOW OBSTRUCTION IN PATIENTS WITH CHRONIC VENOUS DYSFUNCTION

Objective: To quantify the functional venous outflow obstruction with different location and extent of obstruction attributed to previous de ep vein thrombosis. Design: Case-control study. Setting: Vascular Labo ratory, St Mary's Hospital Medical School, London, England. Patients: Two groups: group 1, 25 case patients and 9 control subjects, and grou p 2, 45 case patients and 30 control subjects. Interventions: Ascendin g venography, duplex scanning, air plethysmography, and venous pressur e measurements in the foot and the ann via a 21-gauge butterfly needle . Main Outcome Measures: Venous outflow fraction (VOF), venous outflow resistance (VOR), and arm-foot pressure differential (A-F PD) at rest and after reactive hyperemia. Results: Venous outflow resistance was evaluated in group 1. Twenty-two case patients underwent VOF testing, and 16 had A-F PD measurement performed. Case patients in group 2 unde rwent VOF testing. Signs and symptoms of chronic venous dysfunction me re associated with the anatomical extent of obstruction, Limb swelling and ache were present in most of the patients. Skin changes were note d in about 30% and ulceration in 10% of patients. The results of all t ests showed no evidence of obstruction in control subjects. In most ca se patients with popliteal vein obstruction, test results were similar to those in control subjects: the more proximal the veins involved, t he mure severe the obstruction. In 16 case patients, all 3 tests were performed and agreement between A-F PD and VOR test results was found in 14 of them. The VOF test results agreed with the results of A-F PD and VOR tests in 9 case patients. In group 2, 50% of the limbs with ob struction proximal to the popliteal vein had a reduced VOF, which beca me worst in the limbs with extensive obstruction, particularly when th e iliac veins were involved. Of the 73 limbs tested for VOF in both gr oups, only 7 limbs (9.6%) had their venous outflow markedly reduced by occlusion of the superficial veins. Conclusions: The anatomical exten t of venous obstruction and the development of collateral circulation determine the hemodynamic severity of the chronic venous obstruction. The deep collaterals seem to be more important than the superficial ve nous system in bypassing the obstruction. The VOR and the A-F PD tests can be used to identify those patients who have venous obstruction, w hereas the use of the VOF test may reduce the need for performing the above tests in 50% of the patients.