Pysiological Evaluation of Venous Obstruction in the Post-Thrombotic Leg

Abstract

The accuracy and value of occlusion plethysmography (OP) in assessing post-thrombotic iliac and femoral vein obstruction was determined in 45 patients (85 legs) six months after an acute iliofemoral venous thromboses using contrast phlebography (CP) as reference method. The additional value of femoral venous pressure (FVP) measurements in assessing the physiological importance of iliac vein obstructions was determined in 34 of these patients (60 legs). The sensitivity and specificity of OP in detecting femoral and iliac vein obstructions was 79% and 84% respectively. OP was unable to distinguish femoral from iliac lesions and stenosis from obstructions. A maximum venous outflow (MVO) <30 ml·100 ml−1 ·min−1 was greatly associated with venous obstruction which was very uncommon if the MVO >50 ml·100 ml−1 ·min−1. Resting FVPs were of little value in assessing iliac venous outflow. Exercise pressures and comparison with normal contralateral veins improved the association with anatomical obstruction. A difference in FVP change with exercise exceeding l mmHg as compared to the contralateral leg was most predictive of an iliac vein obstruction. Patients with obvious clinical symptoms of venous outflow obstruction (venous claudication) all had iliac vein obstruction, abnormal OP and an FVP change with exercise exceeding 5 mmHg. This demonstrates the ability of OP and FVP to reflect physiological rather than morphological post-thrombotic venous obstruction.