We would like to thank Saleem et al1Hemodynamics of iliac venous compression syndrome. for his letter and interest in our article. Endovascular treatment for patients with severe iliac vein compression syndrome (IVCS) that addresses all lesions has recognized benefits.2Saleem T. Knight A. Raju S. Diagnostic yield of intravascular ultrasound in patients with clinical signs and symptoms of lower extremity venous disease. Because a small number of patients will experience limited benefits, we have observed that some patients will have severe iliac vein stenosis with mild symptoms and some will have no stenosis but will have obvious venous insufficiency.3Zymvragoudakis V. Spiliopoulos S. Moulakakis K. Lattimer C. Geroulakos G. Incidence and clinical significance of non thrombotic iliac vein lesions. In both cases, the cause could be venous reflux. Thus, such patients will not benefit from stent placement. By analyzing the hemodynamic characteristics of IVCS, we initially identified which patients would more likely benefit from iliac venous stent deployment, which has implications for identifying patients with "pathologic" IVCS and reducing the costs to healthcare systems.4Chen Z.H. Huang Y. Wang L.P. Peng M.Y. Li C. Huang W. Preliminary study of hemodynamics of iliac venous compression syndrome using magnetic resonance imaging.Our study first proposed measuring the flow rate (FR) difference between the common iliac veins and external iliac veins at the stenotic site of the affected limb rather than the FR at baseline in the common iliac vein to determine the possible value of iliac venous stent deployment because large variations exist in the FR at baseline between patients who would and would not benefit from this procedure. Thus, the change in FR might be a more accurate reflection of the effect of stenosis on hemodynamics than is the FR at baseline. We discussed the role of FR differences and collateral vessels in IVCS. Jayaraj and Raju5Iliocaval venous obstruction: endovascular treatment. qualitatively reported that the presence of collateral vessels will often indicate the presence of more severe symptoms, in accordance with Poiseuille's law. Our findings are consistent with their results, indicating that venous hypertension at rest can be "silent" owing to the presence of collateral shunts. Many studies have reported that the presence of severe lower extremity symptoms must indicate the absence of collateral vessels; thus, collateral vessels have only been used as a supplementary indicator for the diagnosis of IVCS. The FR difference will be affected by both stenosis and the presence of collateral shunts and, thus, could better reflect the severity of IVCS hemodynamics.We agree with Gagne et al6Gagne P.J. Gasparis A. Black S. Thorpe P. Passman M. Vedantham S. et al.Analysis of threshold stenosis by multiplanar venogram and intravascular ultrasound examination for predicting clinical improvement after iliofemoral vein stenting in the VIDIO trial. that intravascular ultrasound (IVUS), as the reference standard for the diagnosis of IVCS, can also predict the prognosis of IVCS after endovascular treatment. However, we used nonenhanced magnetic resonance imaging for our patient before surgery. We can select the appropriate sequence parameters to obtain clear three-dimensional (3D) reconstruction images to show the stenosis and simultaneously obtain the hemodynamic parameters with economic advantages. During the procedure, we did not use IVUS. We used 3D digital subtraction angiography (DSA) to perform rotating angiography through 360° of the C-arm to clarify the morphologic characteristics of the veins, determine the overall vein stenosis, and guide vein intervention. According to our experience, 3D-DSA is superior to multiplane angiography in detecting stenosis and filling defects. Compared with IVUS, 3D-DSA also has advantages in evaluating the overall view of venous stenosis.We strongly believe that through the innovation of inspection technology and analysis methods, hemodynamic research of IVCS progression and clinical outcomes will help clarify the relationship between various factors and symptoms and expand our clinical understanding and the prevention of IVCS.7Wang Y. Pierce I. Gatehouse P. Wood N. Firmin D. Xu X.Y. Analysis of flow and wall shear stress in the peroneal veins under external compression based on real-time MR images.References

Hemodynamics of iliac venous compression syndrome.

J Vasc Surg Venous Lymphat Disord. 10: 978-979Saleem T. Knight A. Raju S.

Diagnostic yield of intravascular ultrasound in patients with clinical signs and symptoms of lower extremity venous disease.

J Vasc Surg Venous Lymphat Disord. 8: 634-639Zymvragoudakis V. Spiliopoulos S. Moulakakis K. Lattimer C. Geroulakos G.

Incidence and clinical significance of non thrombotic iliac vein lesions.

Eur J Vasc Endovasc Surg. 58: e125Chen Z.H. Huang Y. Wang L.P. Peng M.Y. Li C. Huang W.

Preliminary study of hemodynamics of iliac venous compression syndrome using magnetic resonance imaging.

J Vasc Surg Venous Lymphat Disord. 10: 131-138.e3

Iliocaval venous obstruction: endovascular treatment.

in: Sidawy A.N. Perler B.A. Rutherford's vascular Surgery and endovascular therapy. 9th ed. Elsevier, : 2116Gagne P.J. Gasparis A. Black S. Thorpe P. Passman M. Vedantham S. et al.

Analysis of threshold stenosis by multiplanar venogram and intravascular ultrasound examination for predicting clinical improvement after iliofemoral vein stenting in the VIDIO trial.

J Vasc Surg Venous Lymphat Disord. 6: 48-56.e1Wang Y. Pierce I. Gatehouse P. Wood N. Firmin D. Xu X.Y.

Analysis of flow and wall shear stress in the peroneal veins under external compression based on real-time MR images.

Med Eng Phys. 34: 17-27Article InfoIdentification

DOI: https://doi.org/10.1016/j.jvsv.2022.02.018

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© 2022 by the Society for Vascular Surgery. Published by Elsevier Inc.

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