DETECTION OF OUTFLOW OBSTRUCTION IN CHRONIC VENOUS INSUFFICIENCY

Purpose: This study compares three different modes for measuring hemodynamically significant outflow obstruction in chronic venous insufficiency: (1) arm-foot venous pressure differential combined with foot venous pressure elevation to reactive hyperemia, (2) outflow fraction determination with plethysmography, and (3) calculation of resistance from simultaneously obtained foot venous pressure and calf volume curves. Methods: The three techniques were compared in 15 normal limbs and 19 limbs with documented previous deep venous thrombosis. Outflow fraction and resistance were also measured after reactive hyperemia was induced. Results: The arm-foot venous pressure measurements delineated patients with grades 1 through 4 obstruction (Raju's grading). Resistance calculations correlated well with this grading except in patients with severe grade 4 obstruction, in whom low resistance was found. Outflow fraction determinations had marked overlapping between the different obstruction grades, substantially decreasing sensitivity to detect hemodynamically important outflow obstructions. No correlation with the resistance calculations was shown. Inducing reactive hyperemia did not alleviate these findings. The failure of the outflow fraction and resistance methods to detect significant obstruction is probably attributable to the use of plethysmographic techniques for volume measurement, which appears to give false-negative results as a result of a regional volume shift within the lower limb. Conclusions: The combination of the arm-foot vein pressure differential and the foot vein pressure elevation after reactive hyperemia seems to be the only reliable test currently available for detecting and grading global chronic obstruction.