Reduced External Iliac Venous Blood Flow Rate Is Associated with Asymptomatic Compression of the Common Iliac Veins

Application of 4D flow MRI for exploring factors affecting haemodynamics of iliac veins in asymptomatic population

BACKGROUND

Haemodynamics plays an important role in the development of vascular disease. There is currently a lack of studies evaluating the characteristics and affecting factors of the iliac vein haemodynamics in clinical practice.

OBJECTIVE

The goal of this study was to use 4D flow MRI to explore the haemodynamic characteristics of iliac veins and its affecting factors in an asymptomatic population.

METHODS

Thirty consecutive volunteers without venous-related symptoms or signs underwent four-dimensional postprocessing of their MRI images. Relevant parameters, the demographic data, common iliac vein-inferior vena cava angle, iliac vein area, tortuosity, iliac vein mean flow, mean velocity was computed and analysed. T tests and Spearman's tests were used for analysing. A P value of 0.05 or less was considered significant.

RESULTS

Height and iliac vein area were positively correlated with flow, while degree of stenosis, and common iliac-inferior vena cava angle were negatively correlated with that. Degree of stenosis was positively correlated with velocity, but the common iliac-inferior vena cava angle and iliac vein tortuosity were negatively correlated with that. The mean flow and velocity of iliac veins in females were lower than males. The mean flow and velocity of the left iliac veins were lower than those of the right.

CONCLUSION

The height, gender, tortuosity, degree of stenosis, common iliac vein-inferior vena cava angle of the iliac vein are important factors that affect flow and velocity of the iliac veins. There were differences in haemodynamic parameters of the bilateral iliac veins.

Quantitative two-dimensional phase-contrast magnetic resonance imaging characterization of lower extremity venous disease: venous reflux versus venous obstruction

Background

Lower extremity venous disease (LEVD) is a complex disorder, and determining the etiology of LEVD is paramount for treatment selection. Two-dimensional phase-contrast magnetic resonance imaging (2D PC-MRI) can provide an objective measure of hemodynamic status and may help differentiate between different etiologies of LEVD. A total of 271 participants, including 256 symptomatic patients with venous lower extremity disease and 15 healthy volunteers, were collected in this cohort study.

Methods

It is a single-center prospective observational study using 2D PC-MRI analysis to assess the hemodynamic characteristics of patients with LEVD among participants recruited between April 2017 and October 2021 at a tertiary hospital. The approval institutional review board number for this study were 201802137B0, 201901058B0, 202100938B0, and 202102344B0. Participants were classified as venous reflux (VR) and venous obstruction (VO) by standard ultrasonography. 2D PC-MRI by 1.5 T scanner revealed stroke volume (SV), forward flow volume (FFV), absolute stroke volume (ASV), mean flux (MF), velocity time integral (VTI), and mean velocity (MV) for each selected venous segments.

Results

2D PC-MRI assessed 167 diseased legs from the 116 VR patients [mean age ± standard deviation (SD): 57.9±12.8 years; 39 males] and 113 diseased legs from the 95 VO patients (mean age ± SD: 66.4±12.8 years; 42 males). 2D PC-MRI analysis demonstrated discrimination ability to differentiate from VR to VO [SV, FFV, ASV, MF, VTI, and MV in the various venous segments, respectively, P≤0.001; area under the curve (AUC) =62-68.8%, P≤0.001 by Mann-Whitney U test]. The ratio data (morbid limb to normal limb) in the same individual with single-leg disease revealed differences between VR and VO (SV, FFV, ASV, and MF in the various venous segments, respectively; P<0.05; AUC =60.2-68.7%, P≤0.05 by Mann-Whitney U test). The most favorable differentiating variables of ratios were FFV in the great saphenous veins [AUC =68.7%, 95% confidence interval (CI): 59.8-77.6%] and ASV in the external iliac veins (AUC =67.4%, 95% CI: 58.7-76.2%).

Conclusions

Quantitative 2D PC-MRI analysis is capable of differentiating VR from VO. It also provides an important diagnostic capability for preoperative evaluation.

Venous Segmental Flow Changes after Superficial Venous Intervention Demonstrating by Quantitative Phase-Contrast Magnetic Resonance Analysis: Preliminary Data from a Longitudinal Cohort Study

The effects of superficial venous intervention on hemodynamics can be quantified using two-dimensional phase-contrast magnetic resonance imaging (2D PC-MRI). Twelve patients received pre- and postintervention 2D PC-MRI analysis using quantitative hemodynamic parameters. Fifteen healthy volunteers served as controls. The 2D PC-MRI results of the target limbs (limbs scheduled for intervention for venous reflux) differed from those of the controls in terms of stroke volume (SV), forward flow volume (FFV), absolute stroke volume (ASV), and mean flux (MF) in all venous segments. The velocity time integral (VTI) and mean velocity (MV) of the popliteal vein (PV) segments were similar between the target limbs and controls preoperatively. After intervention, the target limbs exhibited an increase in VTI and MV in the femoral vein (FV) and PV segments. We compared the target and nontreated limbs of the individual patients preoperatively and postoperatively to minimalize individual bias. All QFlow parameter ratios in the FV segment increased after venous intervention (VTI, p = 0.025; MV, p = 0.024). In the PV segment, FFV and ASV increased significantly (p = 0.035 and 0.024, respectively). After interventions, the volume (FFV and ASV) of the PV segment and the efficiency (VTI and MV) of the FV segment significantly increased.