Morphometric and Hemodynamic Analysis of the Compressed Iliac Vein

Evaluation of hemodynamic characteristics of iliac vein in chronic venous disease and iliac vein compression syndrome patients using magnetic resonance image: A prospective study

OBJECTIVE

The purpose of this study was to explore the characteristics of hemodynamic parameters of iliac vein of patients with chronic venous disease (CVD) using 2D-PC and 4D-Flow MRI and to test the diagnostic and grading efficiency of 2D-PC and 4D-Flow MRI in CVD and iliac vein compression syndrome (IVCS).

METHODS

Consecutive patients with CVD diagnosed in the outpatient department from 2023 to 2024 were enrolled in this study. Demographic data and medical records of the patients were also collected. The CEAP classification, Villalta score, and venous clinical severity score (VCSS) were used to evaluate the severity of lower limb symptoms. After computational tomography venography (CTV) scans to verify iliac vein compression, every patient underwent 2D-PC and 4D-Flow MRI scanning. Circle CVI42 software was used to perform data post processing. Inferior vena cave (IVC), common iliac vein (CIV) and common femoral vein (CFV) were chosen to acquire hemodynamic parameters by MRI. The hemodynamic parameter included flow rate (FR) per cardiac cycle, FR per minute, peak flow velocity (FV) and minimum FV measured by 2D-PC MRI and FR per cardiac cycle, peak FV and pressure gradient measured by 4D-Flow MRI. We analyzed the consistency of hemodynamic parameters between 2D-PC and 4D-Flow MRI, the differences in hemodynamic parameters between symptomatic and asymptomatic limbs and limbs with and without iliac vein compression, and the correlation between parameters and severity of symptoms.

RESULTS

A total of 34 individuals, including 3 healthy volunteers, 15 CVD patients with iliac vein compression, and 16 CVD patients without IVCS, were enrolled in this study. Hemodynamic parameters measured by 2D-PC and 4D-Flow MRI complied with the flow rate conservation and maintained consistency (P<0.01). There was a statistically significant difference in the FR of CIV and FR difference between CIV and CFV measured by 2D-PC and 4D-Flow MRI between symptomatic and asymptomatic limbs (2D-PC MRI: FR of CIV: 6.0±3.1 VS 8.5±5.1, P=0.01. FR Difference: 1.6±2.1 VS 3.6±4.3 P=0.01) (4D-Flow MRI: FR of CIV: 6.9±2.8 VS 8.7±4.2, P=0.04. FR Difference: 3.0±2.8 VS 4.8±3.5 P=0.05), and limbs with and without iliac vein compression (2D-PC MRI: FR of CIV: 5.3±3.0 VS 7.6±4.4, P=0.03. FR Difference: 1.3±2.7 VS 2.8±3.4 P=0.04) (4D-Flow MRI FR of CIV: 6.1±2.6 VS 8.2±3.7, P<0.01. FR Difference: 2.1±3.7 VS 4.6±3.1 P=0.04). The FR of CIV and the FR difference between CIV and CFV were negatively correlated with symptom severity in all affected limbs (2D-PC MRI: FR of CIV:P<0.01 r=-0.3, FR difference: P=0.03, r=-0.3). There was a potential negative correlation between the FR of the CIV in limbs with iliac vein compression and the severity of symptoms (2D-PC MRI: FR of CIV:P=0.07 r=-0.4).

CONCLUSIONS

In conclusion, hemodynamic parameters provided by 2D-PC and 4D-Flow MRI possess the potential clinical value of evaluating CVD and iliac vein compression.

Haemodynamic study of left nonthrombotic iliac vein lesions: a preliminary report

Nonthrombotic iliac vein lesions (NIVLs) are significant causes of chronic venous insufficiency (CVI) in the left lower limb and symptom recurrence following left lower limb varicose vein treatment. The goal of this study was to explore the haemodynamic and morphological characteristics of iliac veins in patients with NIVLs. Pressure at the caudal end of the stenotic left common iliac vein (LCIV) segment, local blood flow velocity, and time-averaged wall shear stress in the stenotic segment exhibited positive correlations with the clinical CVI classification (R = 0.92, p < 0.001; R = 0.94, p < 0.001; R = 0.87, p < 0.001), while the relative retention time showed a negative correlation (R = -0.94, p < 0.001). The pressure difference (∆P) between the two ends of the stenotic segment and the velocity difference (∆V) between the stenotic segment and the caudal end were positively correlated with the clinical classification (R = 0.92, p < 0.001; R = 0.9, p < 0.001). The cross-sectional area stenosis rate and length of the stenotic LCIV segment were positively correlated with the clinical classification (R = 0.93, p < 0.001; R = 0.63, p < 0.001). The results suggest that haemodynamic assessment of the iliac vein could effectively portray blood flow disturbances in stenotic segments of the LCIV, potentially reflecting the degree of iliac vein stenosis. Haemodynamic indicators are correlated with the severity of clinical CVI symptoms.

A comparative study of altered hemodynamics in iliac vein compression syndrome

Introduction: Iliac vein compression syndrome (IVCS) is present in over 20% of the population and is associated with left leg pain, swelling, and thrombosis. IVCS symptoms are thought to be induced by altered pelvic hemodynamics, however, there currently exists a knowledge gap on the hemodynamic differences between IVCS and healthy patients. To elucidate those differences, we carried out a patient-specific, computational modeling comparative study. Methods: Computed tomography and ultrasound velocity and area data were used to build and validate computational models for a cohort of IVCS (N = 4, Subject group) and control (N = 4, Control group) patients. Flow, cross-sectional area, and shear rate were compared between the right common iliac vein (RCIV) and left common iliac vein (LCIV) for each group and between the Subject and Control groups for the same vessel. Results: For the IVCS patients, LCIV mean shear rate was higher than RCIV mean shear rate (550 ± 103 s-1 vs. 113 ± 48 s-1, p = 0.0009). Furthermore, LCIV mean shear rate was higher in the Subject group than in the Control group (550 ± 103 s-1 vs. 75 ± 37 s-1, p = 0.0001). Lastly, the LCIV/RCIV shear rate ratio was 4.6 times greater in the Subject group than in the Control group (6.56 ± 0.9 vs. 1.43 ± 0.6, p = 0.00008). Discussion: Our analyses revealed that IVCS patients have elevated shear rates which may explain a higher thrombosis risk and suggest that their thrombus initiation process may share aspects of arterial thrombosis. We have identified hemodynamic metrics that revealed profound differences between IVCS patients and Controls, and between RCIV and LCIV in the IVCS patients. Based on these metrics, we propose that non-invasive measurement of shear rate may aid with stratification of patients with moderate compression in which treatment is highly variable. More investigation is needed to assess the prognostic value of shear rate and shear rate ratio as clinical metrics and to understand the mechanisms of thrombus formation in IVCS patients.