Hemodynamic significance of collateral blood flow in chronic venous obstruction

Introduction Complaints related to the post-thrombotic syndrome do not always correlate well with the extent of post-thrombotic changes on diagnostic imaging. One explanation might be a difference in development of collateral blood flow. The aim of this study is to investigate the hemodynamic effect of collateralisation in deep venous obstruction. Methodology Resting intravenous pressure of the common femoral vein was measured bilaterally in the supine position of patients with unilateral iliofemoral post-thrombotic obstruction. In addition, pressure in control limbs was also measured in the common femoral vein after sudden balloon occlusion in the external iliac vein. Results Fourteen patients (median age 42 years, 12 female) were tested. In eleven limbs post-thrombotic disease extended below the femoral confluence. Median common femoral vein pressure was 17.0mmHg in diseased limbs compared to 12.8mmHg in controls (p=0.001) and 23.5mmHg in controls after sudden balloon occlusion (p=0.009). Results remained significant after correcting for non-occlusive post-thrombotic disease. Conclusion This study shows that common femoral vein pressure is increased in post-thrombotic iliofemoral deep venous obstruction, though not as much as after sudden balloon occlusion. The latter difference could explain the importance of collateralisation in deep venous obstructive disease and the discrepancy between complaints and anatomical changes; notwithstanding, the presence of collaterals does not eliminate the need for treatment.