Iliac Vein Compression Syndrome Research Articles

Syringe-assisted test-aspiration with mechanical aspiration thrombectomy results in good safety and short-term outcomes in the treatment of patients with deep venous thrombosis.

To evaluate the short-term outcomes and safety of syringe-assisted test-aspiration with mechanical aspiration thrombectomy in the treatment of deep venous thrombosis. This was a single-center, retrospective study of hospitalized patients with iliofemoral and/or inferior vena caval deep venous thrombosis, excluding those with pulmonary embolism. We collected the following patient data from the electronic medical records: age, sex, provoked/unprovoked deep venous thrombosis, symptom duration, thrombosed segments, and the presence of a tumor, thrombophilia, diabetes, and/or iliac vein compression syndrome. Venography and computed tomographic venography were performed in all patients before the procedure. All patients underwent syringe-assisted test-aspiration with mechanical aspiration thrombectomy under local anesthesia and sedation, and all received low-molecular-weight heparin peri-operatively. All patients underwent implantation of an inferior vena caval filter. Rivaroxaban was administered post-procedure, instead of heparin, for 3-6 months, with lower extremity compression. Overall, 29 patients with deep venous thrombosis underwent syringe-assisted test-aspiration with mechanical aspiration thrombectomy from January 2022 to October 2022 in our institution. Technical success (>70% thrombus resolution) was achieved in all patients, and using a single procedure in 25/29 patients (86%). Concomitant stenting was performed in 18/29 (62%) of the patients, and 21/29 (69%) underwent angioplasty. The median (interquartile range) procedure time was 110min (100-122), the median intra-operative bleeding volume was 150mL (120-180), and the median decrease in the hemoglobin concentration from pre- to post-operative was 7g/L (4-14). The median follow-up duration was 7 months (5-9). All patients obtained symptomatic relief, and 27/29 achieved near-remission or full remission (combined total). No patients experienced peri-operative bleeding complications, or symptom recurrence or post-thrombectomy syndrome during follow-up. The short-term outcomes following syringe-assisted test-aspiration with mechanical aspiration thrombectomy in the treatment of deep venous thrombosis were excellent, and the procedure was safe.

Fibulin-1 promotes intimal hyperplasia after venous stent implantation through ACE mediated angiotensin II signaling

ObjectiveStent intimal hyperplasia leads to in stent restenosis and thrombosis. This study determined whether Fibulin-1 activity in smooth muscle cells (SMCs) contributes to stent restenosis or thrombosis. MethodsStent implantation was conducted in a pig model. Target vessel samples were stained and analyzed by protein mass spectrometry. Cell experiments and Fibulin-1 SMC specific knockout mice (Fbln1SMKO) were used to investigate the mechanism of Fibulin-1 induced SMC proliferation and thrombosis. ResultsSMC proliferation and phenotypic transition are the main pathological changes of intimal hyperplasia in venous stents. Protein mass spectrometry analysis revealed a total of 67 upregulated proteins and 39 downregulated proteins in intimal hyperplasia after stent implantation compared with normal iliac vein tissues. Among them, Fibulin-1 ranked among the top proteins altered. Fibulin-1 overexpressing human SMCs (Fibulin-1-hSMCs) showed increased migration and phenotypic switching from contractile to secretory type and Fibulin-1 inhibition decreased the activity of SMCs. Mechanistically, Fibulin-1-hSMCs displayed increased levels of angiotensin converting enzyme (ACE) expression and angiotensin II signaling. Inhibition of ACE or angiotensin II signaling alleviated the migration of Fibulin-1-hSMCs. Using Fibulin-1 SMC specific knockout mice (Fbln1SMKO) and venous thrombosis model, we demonstrated that Fibulin-1 deletion attenuated intimal SMCs proliferation and thrombosis. Further, Fibulin-1 concentration was high in iliac vein compression syndrome (IVCS) patients treated with stent and was an independent predictor of venous insufficiency. ConclusionsFibulin-1 promotes SMC proliferation partially through ACE secretion and angiotensin II signaling after stent implantation. Fibulin-1 plays a role in venous insufficiency syndrome, implicating the protein in the detection and treatment of IVCS.

A prognostic nomogram for recurrence survival in post-surgical patients with varicose veins of the lower extremities

Varicose veins of the lower extremities (VVLEs) are prevalent globally. This study aims to identify prognostic factors and develop a prediction model for recurrence survival (RS) in VVLEs patients after surgery. A retrospective analysis of VVLEs patients from the Third Hospital of Nanchang was conducted between April 2017 and March 2022. A LASSO (Least Absolute Shrinkage and Selection Operator) regression model pinpointed significant recurrence predictors, culminating in a prognostic nomogram. The model’s performance was evaluated by C-index, receiver operating characteristic (ROC) curves, calibration plots, and decision curve analysis (DCA). The LASSO regression identified seven predictors for the nomogram predicting 1-, 2-, and 5-year RS. These predictors were age, body mass index (BMI), hypertension, diabetes, the Clinical Etiological Anatomical Pathophysiological (CEAP) grade, iliac vein compression syndrome (IVCS), and postoperative compression stocking duration (PCSD). The nomogram’s C-index was 0.716, with AUCs (Area Under the Curve scores) of 0.705, 0.725, and 0.758 for 1-, 2-, and 5-year RS, respectively. Calibration and decision curve analyses validated the model’s predictive accuracy and clinical utility. Kaplan–Meier analysis distinguished between low and high-risk groups with significant prognostic differences (P < 0.05). This study has successfully developed and validated a nomogram for predicting RS in patients with VVLEs after surgery, enhancing personalized care and informing clinical decision-making.

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 ± 103s-1 vs. 113 ± 48s-1, p = 0.0009). Furthermore, LCIV mean shear rate was higher in the Subject group than in the Control group (550 ± 103s-1 vs. 75 ± 37s-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.

Mechanism of effect of stenting on hemodynamics at iliac vein bifurcation

When performing stent intervention for iliac vein compression syndrome, the operator selects the appropriate stent and determines its implantation depth according to the type and severity of iliac vein stenosis in the patient. However, there is still uncertainty regarding how the structure of the stent and its implantation depth affect hemodynamics at the site of lesion. In this paper, we analyzed three commonly used stents (Vena stent from Venmedtch, Venovo from Bard, and Smart stent from Cordis) with different implantation depths (0, 10, 20 mm) using computational fluid dynamics (CFD). We focused on evaluating hemorheological parameters such as time-averaged wall shear stress (TAWSS), oscillatory shear index (OSI), etc., within one pulsatile cycle after stent implantation. The correlation between geometric parameters of the stents and hemodynamic indicators was assessed using Pearson correlation coefficient (r), which was further validated through PIV velocity measurement experiment. The results revealed that an increase in implantation depth led to a more pronounced disturbance effect on blood flow at bifurcation for densely arranged support body-type stents. This effect was particularly significant during periods of smooth blood flow. On the other hand, crown-shaped Vena stents exhibited relatively less disruption to blood flow post-implantation. Implantation depth showed a strong negative correlation with TAWSS but a strong positive correlation with OSI and RRT. These findings suggest an increased risk of thrombosis at iliac vein bifurcation following stent placement. Amongst all three tested stents, Vena Stent demonstrated more favorable periodic parameters after implantation compared to others. These results provide valuable theoretical insights into understanding contralateral circulation thrombosis associated with iliac vein stenting.

Clinical Outcomes at 3 Years After Stenting for Thrombotic and Non-thrombotic Iliac Vein Compression Syndrome Patients.

Iliac vein stenting for the treatment of iliac vein compression syndrome (IVCS) has been gradually developed. This article investigated the long-term patency and improvement of clinical symptoms after endovascular stenting for iliac vein obstruction patients. From 2020 to 2022, 83 patients at a single institution with IVCS underwent venous stent implantation and were divided into two groups: non-thrombotic IVCS (n = 55) and thrombotic IVCS (n = 28). The main stent-related outcomes include technical success, long-term patency, and thrombotic events. The technical success rate of all stent implantation was 100%. The mean length of hospital stay and cost were higher in the thrombotic IVCS group than in the non-thrombotic ICVS group, as well as the length of diseased vessel segment and the number of stents implanted were higher than in the control non-thrombotic group. The 1-, 2-, and 3-year patency rates were 85.4%, 80% and 66.7% in the thrombosis group, which were lower than 93.6%, 88.7%, and 87.5% in the control group (P = .0135, hazard ratio = 2.644). In addition, patients in both groups had a foreign body sensation after stent implantation, which resolved spontaneously within 1 year after surgery. Overall, there were statistically significant differences in long-term patency rate outcome between patients with thrombotic and non-thrombotic IVCS, the 1-, 2-, and 3-year patency rates in non-thrombotic IVCS patients were higher than those in thrombotic IVCS patients.

A cadaver study evaluating intraluminal anomalies of the left common iliac vein

ObjectiveIntraluminal anomalies within the left common iliac vein, characteristic of iliac vein compression syndrome, are thought to result from compression by and pulsation of the overlying right common iliac artery. This cadaver study was designed to expand on the existing literature by surveying and photographing these spurs in addition to exploring whether certain factors, inherent to the cadaver, are associated with spur presence. MethodsDissection to expose the aorta, inferior vena cava, and common iliac arteries and veins was performed in 51 cadavers. The spinal level at which the iliac vein confluence occurred was noted. The point at which the right common iliac artery crossed the left common iliac vein was examined for plaque presence. The overlying arterial structures were then transected to expose the venous system. The inferior vena cava was incised to facilitate observation into the mouth and full extent of the left common iliac vein. Spurs were photographed and documented. Statistical analysis was conducted to determine whether sex, body mass index (BMI), plaque presence, or level of the iliac vein confluence are associated with spur presence. ResultsSpurs within the left common iliac vein were observed in 16 of 51 cadavers (31.4%). All spurs were located at the point that the right common iliac artery crossed the left common iliac vein. Using1 the classification system established by McMurrich, 67% of spurs (n = 10) were marginal and triangular; 25% (n = 4) were columnar. One marginal, linear spur (6%) and one partially obstructed spur with multiple synechiae (6%) were observed. Among this population, males were 73% less likely to have a spur (odds ratio, 0.269; P = .041). No significant relationship was found between plaque presence and spur presence (odds ratio, 0.933; P = .824) and no significant differences were noted between BMI and spur presence (χ2 = 1.752, P = .625). Last, a significantly greater percent of spurs was found within cadavers with an iliac vein confluence located at the L5/S1 disc space (χ2 = 9.650; P = .002). ConclusionsStudy findings show that spurs are more common when the confluence of the common iliac veins occurs at a lower spinal level. The level of the iliac vein confluence may be important in identifying patients at increased risk of venous disease. The findings also suggest that plaque within the right common iliac artery and BMI display no distinct relationship with spur presence. Further investigation is needed to understand exactly what factors lead to spur formation.

Ultrasound characteristics of abdominal vascular compression syndromes.

Abdominal vascular compression syndrome (AVCS) is caused by the compression of abdominal blood vessels by adjacent structures or the compression of abdominal organs by neighboring blood vessels. Such compressions can result in a variety of clinical symptoms. They are not commonly seen in ultrasound practices, and their presence may have been underrecognized and underdiagnosed. This article reviews the clinical features, ultrasound characteristics, and diagnostic criteria of four types of AVCS, namely, celiac artery compression syndrome, renal vein compression syndrome, iliac vein compression syndrome, and superior mesenteric artery syndrome to increase awareness of these conditions among ultrasound practitioners. The ultrasound criteria for AVCS are primarily based on studies with small sample sizes, and therefore, it is important to exercise caution if these criteria are used.

Effectiveness of iliac vein stenting combined with endovenous laser treatment of recurrent varicose veins associated with iliac vein compression.

Iliac vein compression syndrome (IVCS) is an underlying cause of varicose vein (VV) recurrence after venous surgery. However, the management of recurrent varicose veins (RVVs) combined with IVCS has rarely been reported. This study aimed to investigate the outcomes of a one-stop procedure to correct outflow obstruction and superficial reflux for patients with RVVs and IVCS. A retrospective analysis was conducted of 102 consecutive patients diagnosed with RVVs. Computed tomography venography (CTV) was performed to confirm IVCS. The cases were divided into 2 groups: the IRVVs group, including patients with RVVs and IVCS (n=48), and the RVVs group, including patients with RVVs only (n=54). The characteristics, vein reflux, and clinical, etiological, anatomical, and pathophysiological (CEAP) distribution were investigated. Then, the IRVVs group patients who underwent endovenous laser ablation (EVLA) (n=39) were divided into a further 2 groups: the EVLA + S group (n=19), who received EVLA and stenting of iliac vein, and the EVLA group (n=20), who received EVLA treatment alone. The great/small saphenous vein (GSV/SSV) trunk occlusion, VV recurrence, visual analogue scale (VAS), and venous clinical severity score (VCSS) were investigated. The prevalence rate of femoral vein reflux was 81.2% in IRVVs group and 50% in RVVs group (P<0.05). In the IRVVs group, 72.9% of patients manifested as CEAP clinical class >3, which was higher than that in RVVs group (48.1%) (P<0.05). The 12-month GSV/SSV occlusion rate in the EVLA + S and EVLA groups were 94.7% and 90.0%, respectively. Totals of 9 patients in EVLA + S group and 6 patients in EVLA group had active venous ulcers, and the ulcer healing time in EVLA + S group was significantly shorter (27.22±7.12 vs. 46.67±9.83 days, P<0.05). The reductions in the VAS and VCSS values between baseline, 1 month, and 12 months in the EVLA + S group were more obvious than those in EVLA group (P<0.05). The one-stop combination treatment of iliac venous stenting and EVLA in patients with RVVs and IVCS is safe and effective and provides prominent symptom relief, improved quality of life, and a more satisfactory ulcer healing than EVLA alone.

Efficacy of modified time of flight magnetic resonance venography in diagnosis of iliac vein compression syndrome

ObjectiveWe investigated the diagnostic efficacy of modified time of flight magnetic resonance venography (mTOF-MRV) for iliac vein compression syndrome diagnosis by optimizing the scanning parameters and improving image quality. MethodsA retrospective study was conducted on 69 patients who underwent routine time of flight magnetic resonance venography (TOF-MRV) and 85 patients who received mTOF-MRV. Assessment of image quality of the two methods was performed by two radiologists using a four-point method. The sensitivity, specificity, positive and negative predictive values of TOF-MRV and mTOF-MRV in the diagnosis of significant iliac vein compression (stenosis >50%) were analyzed by calculating the iliac vein stenosis rates of the two methods and using digital subtraction angiography (DSA) as the gold standard. ResultsInter-observer assessment of objective data measurement revealed excellent agreement {ICC [95% confidence interval (CI)]: 0.972 (0.953 to 0.983) for TOF-MRV and 0.979 (0.965 to 0.988) for m-TOF MRV, 0.976 (0.960 to 0.986) for DSA}. The mean error of stenosis rate of mTOF-MRV was markedly smaller than that of TOF-MRV (p < 0.05). Sensitivity, specificity, positive and negative predictive values of TOF-MRV in the diagnosis of significant stenosis were 100%, 95%, 67% and 100%, respectively. The sensitivity, specificity, positive and negative predictive values of mTOF-MRV were 100%. The mean image score for the mTOF-MRV was 3.63 ± 0.59, which was significantly higher compared with that of TOF-MRV (2.19 ± 0.42). ConclusionmTOF-MRV has better image quality and can accurately diagnose venous stenosis. Therefore, it can be used for the detection of iliac vein compression syndrome and further assessment after endovascular interventions.

Clinical efficacy of ZelanteDVT™ catheter rheolytic thrombectomy in the single-session treatment of patients with subacute deep venous thrombosis.

To evaluate the clinical efficacy and safety of novel ZelanteDVT™ catheter rheolytic thrombectomy in the single-session endovascular management of subacute deep venous thrombosis (DVT). A retrospective study was performed on 31 patients with subacute DVT who underwent ZelanteDVT™ catheter rheolytic thrombectomy. Procedure data, associated complications, and venous patency score were recorded. The deep venous patency and post-thrombotic syndrome (PTS) rate were assessed in all patients during follow-up visits. After procedure, 19.4% (6/31) patients improved to grade III thrombus removal, while the remaining patients improved to grade II. Significant iliac vein compression syndrome was identified in 54.8% (17/31) patients, and 82.4% (14/17) of them received stent implantation. No serious procedure-related complications occurred. The median follow-up time was 13months. The primary patency rate at 12months was 83.87%, and the incidence of PTS was 19.35%. This novel rheological thrombectomy catheter seems to have a promising application prospect for single-session treatment of subacute DVT.

An ultrasound imaging and computational fluid dynamics protocol to assess hemodynamics in iliac vein compression syndrome

ObjectiveElevated shear rates are known to play a role in arterial thrombosis; however, shear rates have not been thoroughly investigated in patients with iliac vein compression syndrome (IVCS) owing to imaging limitations and assumptions on the low shear nature of venous flows. This study was undertaken to develop a standardized protocol that quantifies IVCS shear rates and can aid in the diagnosis and treatment of patients with moderate yet symptomatic compression. MethodsStudy patients with and without IVCS had their iliac vein hemodynamics measured via duplex ultrasound (US) at two of the following three vessel locations: infrarenal inferior vena cava (IVC), right common iliac vein, and left common iliac vein, in addition to acquiring data at the right and left external iliac veins. US velocity spectra were multiplied by a weighted cross-sectional area calculated from US and computed tomography (CT) data to create flow waveforms. Flow waveforms were then scaled to enforce conservation of flow across the IVC and common iliac veins. A three-dimensional (3D), patient-specific model of the iliac vein anatomy was constructed from CT and US examination. Flow waveforms and the 3D model were used as a basis to run a computational fluid dynamics (CFD) simulation. Owing to collateral vessel flow and discrepancies between CT and US area measurements, flows in internal iliac veins and cross-sectional areas of the common iliac veins were calibrated iteratively against target common iliac flow. Simulation results on mean velocity were validated against US data at measurement locations. Simulation results were postprocessed to derive spatial and temporal values of quantities such as velocity and shear rate. ResultsUsing our modeling protocol, we were able to build CFD models of the iliac veins that matched common iliac flow splits within 2% and measured US velocities within 10%. Proof-of-concept analyses (1 subject, 1 control) have revealed that patients with IVCS may experience elevated shear rates in the compressed left common iliac vein, more typical of the arterial rather than the venous circulation. These results encourage us to extend this protocol to a larger group of patients with IVCS and controls. ConclusionsWe developed a protocol that obtains hemodynamic measurements of the IVC and iliac veins from US, creates patient-specific 3D reconstructions of the venous anatomy using CT and US examinations, and computes shear rates using calibrated CFD methods. Proof-of-concept results have indicated that patients with IVCS may experience elevated shear rates in the compressed left common iliac vein. Larger cohorts are needed to assess the relationship between venous compression and shear rates in patients with IVCS as compared with controls with noncompressed iliac veins. Further studies using this protocol may also give promising insights into whether or not to treat patients with moderate, yet symptomatic compression.

CFD Study of the Effect of the Angle Pattern on Iliac Vein Compression Syndrome.

Iliac vein compression syndrome (IVCS, or May-Thurner syndrome) occurs due to the compression of the left common iliac vein between the lumbar spine and right common iliac artery. Because most patients with compression are asymptomatic, the syndrome is difficult to diagnose based on the degree of anatomical compression. In this study, we investigated how the tilt angle of the left common iliac vein affects the flow patterns in the compressed blood vessel using three-dimensional computational fluid dynamic (CFD) simulations to determine the flow fields generated after compression sites. A patient-specific iliac venous CFD model was created to verify the boundary conditions and hemodynamic parameter set in this study. Thirty-one patient-specific CFD models with various iliac venous angles were developed using computed tomography (CT) angiograms. The angles between the right or left common iliac vein and inferior vena cava at the confluence level of the common iliac vein were defined as α1 and α2. Flow fields and vortex locations after compression were calculated and compared according to the tilt angle of the veins. Our results showed that α2 affected the incidence of flow field disturbance. At α2 angles greater than 60 degrees, the incidence rate of blood flow disturbance was 90%. In addition, when α2 and α1 + α2 angles were used as indicators, significant differences in tilt angle were found between veins with laminar, transitional, and turbulent flow (p < 0.05). Using this mathematical simulation, we concluded that the tilt angle of the left common iliac vein can be used as an auxiliary indicator to determine IVCS and its severity, and as a reference for clinical decision making.

Iliac Vein Compression Syndrome: A Cause of Deep Vein Thrombosis

&lt;p&gt;下肢深層靜脈栓塞在臨床上是一個常見的疾病。它的發生不只常見危險因子：包含長期久站、臥床、年齡大、靜脈曲張、服用避孕藥、惡性腫瘤等，人體結構上的異常也是可能的原因。髂靜脈壓迫症候群(Iliac vein compression syndrome)，亦稱為May-Thurner syndrome，是一個極少被診斷的疾病，成因是左總髂靜脈受到右總髂動脈和後方腰椎的壓迫，造成靜脈血流滯阻。這個解剖異常約存在於20%的人口，但是常因病人有許多危險因子而未安排進一步的檢查，而沒有診斷出這個疾病。May-Thurner syndrome若症狀嚴重需置放支架，保持血管暢通才能避免復發。這篇個案報告是描述這個罕見被診斷的疾病，在臨床上病人有下肢深層靜脈栓塞，考量到這個重要疾病對病人會有很大的幫助。&lt;/p&gt; &lt;p&gt;&amp;nbsp;&lt;/p&gt;&lt;p&gt;Deep vein thrombosis as a common clinical syndrome finds its major risk factors in prolonged standing, immobility, old age, varicose veins, pregnancy, oral contraceptives, and cancer. However, an anatomical variant can also lead to blood clots in the lower extremity. May-Thurner syndrome, also known as iliac vein compression syndrome, is a rare condition in which the left common iliac vein is compressed by the right common iliac artery, thus increasing the risk of deep vein thrombosis in the left extremity. While this anatomic finding is present in over 20% of the population, most go undiagnosed as patients presenting with deep vein thrombosis have other accompanying risk factors. For severe May-Thurner syndrome, endovascular venous stenting may actually be necessary to prevent recurrence. In this case report, an 85-year-old woman with progressive swelling of left lower extremity was diagnosed with May-Thurner syndrome. When evaluating patients with unilateral leg pain and swelling, clinicians should keep in mind the possibility of May-Thurner syndrome as another possible risk factor of deep vein thrombosis.&lt;/p&gt; &lt;p&gt;&amp;nbsp;&lt;/p&gt;

Effect of stent treatment on hemodynamics in iliac vein compression syndrome with collateral vein.

Iliac vein compression syndrome (IVCS) leads to blood flow obstruction in the lower extremities and is usually treated with stents, but stenting may worsen the hemodynamics and increase the risk of thrombosis in the iliac vein. The present work evaluates the advantages and disadvantages of the stent on IVCS with a collateral vein. The computational fluid dynamics method is adopted to analyze the preoperative and postoperative flow fields in a typical IVCS. The geometric models of the iliac vein are constructed from medical imaging data. The porous model is used to simulate the flow obstruction in IVCS. The preoperative and postoperative hemodynamic characteristics in the iliac vein are obtained, e.g., the pressure gradient at two ends of the compressive region and the wall shear stress. It is found that the stenting restores the blood flow in the left iliac vein. Impacts of the stent are classified into short-term and long-term effects. The short-term effects are beneficial in relieving IVCS, i.e., shortening the blood stasis and reducing the pressure gradient. The long-term effects increase the risk of thrombosis in the stent, i.e., enlarging wall shear stress due to a large corner and a diameter constriction in the distal vessel, and suggests the need to develop a venous stent for IVCS.

Iliac vein compression syndrome by lumbar degenerative changes is associated with deep vein thrombosis after total knee arthroplasty.

This study aimed to identify whether iliac vein compression syndrome(IVCS) is associated with deep vein thrombosis(DVT) after total knee arthroplasty(TKA) and whether lower lumbar degenerative changes were risk factors for IVCS. A total of 259 consecutive patients who underwent TKA from January 2019 to March 2022 was retrospectively reviewed. Preoperative plain radiographs of lumbar spines and CT venography (CTV) for DVT diagnosis at postoperative 7days were performed in all patients. Imaging findings of lower lumbar degenerative changes were analyzed on plain radiograph including lateral osteophytes, scoliosis, lateralolisthesis, retrolisthesis, anterolisthesis, and lower lumbar lordosis angle (LLLA). Percent compression at the left common iliac vein (LCIV) and right common iliac vein (RCIV) as well as DVT were evaluated on CTV. Moreover, IVCS was defined as greater than 50% of compression of the iliac vein on CTV. DVT occurred in 79 patients (30.5%) after TKA. The overall occurrence of DVT was significantly higher in patients with IVCS of LCIV (52.8%) than those without (18.8%, P < 0.001). When DVT was further subdivided, compared to non-IVCS, IVCS of LCIV was significantly associated with bilateral DVT (P < 0.001, both), especially distal DVT (P < 0.001, both), and IVCS of RCIV was significantly associated with right-side DVT (P = 0.031), especially popliteal (P = 0.008) and distal DVT(P = 0.011). Female patients (OR: 3.945, P = 0.039), presence of left osteophyte (OR: 2.348, P = 0.006), and higher LLLA (OR: 1.082, P < 0.001) were significantly associated with IVCS of LCIV, and presence of right osteophyte (OR: 3.494, P = 0.017) was significantly associated with IVCS of RCIV. IVCS was significantly associated with DVT after TKA and lumbar degenerative changes with lateral osteophytes and hyperlordosis were significant risk factors for IVCS.

Multi-factor analysis of failure for modified single-session Angiojet rheolytic thrombectomy in treatment of acute iliofemoral venous thrombosis from iliac vein compression syndrome.

To explore the risk factors of failure for modified single-session Angiojet rheolytic thrombectomy combined with directed iliac vein stenting, directed filter retrieval in the treatment of iliac vein compression with iliofemoral vein thrombosis. During September 2017 to September 2021, 278 patients with DVT were retrospectively analyzed and 203 were eligible for inclusion. All patients were tried to take modified single-session Angiojet rheolytic thrombectomy combined with directed iliac vein stenting, directed filter retrieval treatment. The perioperative factors were analyzed between groups: group 1-modified single-session therapy succeed, and group 2-modified single-session therapy failed. The high risk factors of failure group were evaluated by logistic regression analysis. 48 patients failed in modified single-session therapy, up to 23.64%. Single factor analysis indicated that there were five independent risk factors related with the failure (p < 0.05), including course of disease longer than 7days, lumbar degeneration-related iliac vein compression syndrome (dIVCS), antegrade vein access, balloon-assisted cracking thrombus, and suction time. Logistic regression analysis indicated that course of disease longer than 7days (OR = 19.642.95%CI:6.776∼56.933), dIVCS (OR = 11.586.95%CI:4.016∼33.427) were high risk factors for modified single-session therapy failed, antegrade vein access (OR = 0.171.95%CI:0.047∼0.614) and balloon-assisted cracking thrombus (OR = 0.157.95%CI:0.045∼0.542) were protective factors for therapy failure (p < 0.05). Long course of disease and dIVCS are the high risk factors for failure of modified single-session Angiojet rheolytic thrombectomy combined with directed iliac vein stenting, directed filter retrieval in the treatment of iliac vein compression syndrome (IVCS). But, antegrade vein access and balloon-assisted cracking thrombus intraoperatively may improve the success rate of modified single-session treatment.

Minimal vessel area predicts in-stent restenosis in nonthrombotic iliac vein compression syndrome after stenting.

To the Editor: Iliac vein compression syndrome (IVCS) is a well-documented anatomic abnormality characterized by the compression of iliac veins from the adjacent artery and vertebra. Depending on whether deep vein thrombosis was co-existing, IVCS could be classified into thrombotic and nonthrombotic lesions. Endovascular procedures have become the mainstream treatment for nonthrombotic IVCS.[1] In most cases, balloon dilation is insufficient to treat nonthrombotic IVCS because the venous wall is easily recoiled. Stenting for iliac vein lesion is therefore necessary for keeping enlargement of the venous lumen. However, stent implantation may bring side effects such as in-stent thrombosis and restenosis. In-stent restenosis (ISR) caused by intimal hyperplasia remains a major drawback of stenting in arterial diseases. However, the evidence about the occurrence and predictors of ISR in nonthrombotic IVCS is limited. We therefore conducted this research to identify the incidence of ISR and explore the potential predictors of ISR in patients with nonthrombotic IVCS. Patients with nonthrombotic IVCS, who accepted stenting between 2017 and 2020 in our vascular department, were retrospectively analyzed. The study protocol was approved by the Human Research Ethics Committees of Zhongshan hospital, Fudan University (No. B2017-115), and the patient informed consent was waived. Every limb was considered as an independent data in all statistical analysis. Patients underwent stenting under local anesthesia. To precisely evaluate the venous lesion, intravascular ultrasound was performed for each limb. Diameter or area of venous stenosis was calculated using the formula: (1–minimal vessel diameter [area]/reference vessel diameter [area]) × 100%. Patients received a combination of aspirin and rivaroxaban for at least 6 months after stenting, and follow-up was suggested at 3, 6, 12 months and yearly thereafter. During the follow-up, all computed tomography (CT) scans were performed with a 64-slice detector (Optima CT 660, General Electric and Aquilion 64, Tokyo, Japan) for all subjects. Coronal, sagittal, and oblique pictures were reformatted, and the degree and location of ISR were evaluated independently by a radiologist and a vascular surgeon. In this study, ISR was defined as any degree of stenosis. Limbs could be classified into the ISR and non-ISR group based on whether stenosis has occurred. Continuous data were presented as mean ± standard deviation or median (Q1, Q3) according to their distribution, while categorical data were presented as counts (percentages). Comparison between the two groups was performed using the χ2 test, Mann–Whitney U test, Student's t-test, or Fisher's exact test where appropriate. Multivariable logistic regression analysis was performed by including all potential predictors (P < 0.10 in univariable analyses). A P value (two-sided) <0.05 was recognized as statistically significant; and analyses were conducted using SPSS Statistics (version 23, IBM, Armonk, NY, USA). A total of 68 patients with 78 limbs were eligible for further analysis. The age was 63.94 ± 8.02 years and more than half of them were female. The body mass index (BMI) was 24.97 ± 2.94 kg/m2. The most common comorbidities were hypertension and diabetes. Most of the iliac vein compression (56/78, 71.79%) occurred in the left leg and 10 patients had bilateral lesions. According to the Clinical–Etiology–Anatomy–Pathophysiology classification, there were 6 limbs of C3 (edema), 53 limbs of C4 (skin changes such as pigmentation, eczema, and induration), 7 limbs of C5 (healed venous ulcer), and 12 limbs of C6 (active venous ulcer). During the follow-up period, 10 patients with 10 limbs presented with ISR (12.8%). ISR mainly occurred at the middle of stent (8/10), a location which was close to the original compression point; the remaining two ISR occurred at the proximal segment of stent. The median time of ISR was 7.5 months (3.0–13.0 months) after stenting. The comparison of demographic and anatomic characteristics between two groups was displayed in Table 1. Specifically, the ISR group tended to be older and had a higher percentage of female patients but a lower BMI than non-ISR group. In contrast, anatomic parameters did not significantly differ between the two groups. But there was a trend toward a lower minimal vessel area (MVA) (43.16 ± 16.68 mm2vs. 55.72 ± 19.70 mm2, t = –1.915, P = 0.059) and a higher percent area stenosis (66.35 ± 12.55% vs. 59.93 ± 10.92%, t = 1.703, P = 0.093) in the ISR group compared with non-ISR group, although these differences did not reach statistical significance. In the multivariable logistic regression analysis, area stenosis was not included for avoiding the colinearity. Table 1 - Baseline and anatomic characteristics of the ISR and non-ISR group after stenting in iliac vein compression syndrome patients. Items ISR (n = 10) Non-ISR (n = 68) U/t/χ 2 P values Age (years) 68.00 ± 7.48 63.24 ± 7.95 −1.972∗ 0.058 Female 8 (80.0) 34 (50.0) 3.157† 0.076 BMI (kg/m2) 23.50 ± 2.71 25.18 ± 2.93 −1.764∗ 0.078 Left side 9 (90.0) 47 (69.12) 0.988† 0.320 CEAP classification|| −0.263∗ 0.813 C3 1 (10.0) 5 (7.4) C4 6 (60.0) 47 (69.1) C5 1 (10.0) 6 (8.8) C6 2 (20.0) 10 (14.7) MVD (mm) 3.19 ± 1.55 3.66 ± 1.45 1.054∗ 0.292 RVD (mm) 10.67 ± 2.62 10.22 ± 2.17 0.596‡ 0.553 Percent diameter stenosis (%) 67.88 ± 18.42 63.26 ± 13.39 1.196∗ 0.232 MVA(mm2) 43.16 ± 16.68 55.72 ± 19.70 1.915‡ 0.059 RVA (mm2) 139.29 ± 60.01 142.86 ± 44.18 0.228‡ 0.820 Percent area stenosis (%) 66.35 ± 12.55 59.93 ± 10.92 1.703‡ 0.093 Stent type 0.682§ Luminexx 2 (20.0) 18 (26.5) Wallstent 7 (70.0) 47 (69.1) Other 1 (10.0) 3 (4.4) Stent number 0.506§ 1 9 (90.0) 64 (94.1) 2 1 (10.0) 4 (5.9) Stent size 0.632∗ 0.527 12 mm 2 (20.0) 10 (14.7) 14 mm 3 (20.0) 33 (48.5) 16 mm 3 (30.0) 20 (29.4) 18 mm 2 (20.0) 5 (7.4) Stent length 0.688∗ 0.491 4 cm 0 (0) 1 (1.5) 6 cm 2 (20.0) 11 (16.2) 7 cm 0 (0) 1 (1.5) 8 cm 0 (0) 9 (13.2) 9 cm 5 (50.0) 31 (45.6) 10 cm 1 (10.0) 6 (8.8) 12 cm 2 (20.0) 9 (13.2) Stent entering into IVC 4 (40.0) 29 (42.6) 0.025† 0.854 Post-stenting MVD (mm) 10.27 ± 1.74 10.09 ± 2.28 0.235‡ 0.815 Post-stenting RVD (mm) 11.36 ± 1.57 12.32 ± 1.63 −0.982‡ 0.235 Residual diameter stenosis (%) 9.50 ± 9.26 17.74 ± 16.97 −1.498‡ 0.138 Post-stenting MVA (mm2) 131.84 ± 48.52 131.05 ± 43.63 0.053‡ 0.958 Post-stenting RVA (mm2) 149.28 ± 53.41 159.77 ± 51.81 −0.596‡ 0.553 Luminal diameter increased (mm) 7.08 ± 2.57 6.43 ± 2.20 0.851‡ 0.397 Luminal area increased (mm2) 88.68 ± 43.07 75.33 ± 36.50 1.056‡ 0.294 Residual area stenosis (%) 11.29 ± 10.91 16.55 ± 16.61 −0.968‡ 0.336 Red blood cells (×1012/L) 4.29 ± 0.66 4.38 ± 0.51 −0.830∗ 0.407 Hemoglobin (g/L) 125.40 ± 15.05 133.34 ± 14.12 −1.647‡ 0.104 Platelets (×109/L) 221.80 ± 61.47 196.35 ± 47.82 1.514‡ 0.134 White blood cells (×109/L) 5.33 ± 1.23 5.90 ± 1.60 −1.082‡ 0.283 Fibrinogen (mg/dL) 276.60 ± 48.48 268.19 ± 63.77 −0.710‡ 0.478 Data are presented as n (%) or mean ± standard deviation.∗U values.†χ2 values.‡t values.§Fisher's exact test was applied.||The Clinical–Etiology–Anatomy–Pathophysiology (CEAP) classification, C3 means edema, C4 means skin changes, such as pigmentation, eczema, and induration, C5 means healed venous ulcer, C6 means active venous ulcer. BMI: Body mass index; CEAP: Clinical–Etiology–Anatomy–Pathophysiology; ISR: In-stent restenosis; IVC: Inferior vena cava; MVA: Minimal vessel area; MVD: Minimal vessel diameter; RVA: Reference vessel area; RVD: Reference vessel diameter; –: Not avaliable. The receiver operating characteristic (ROC) curve was then conducted for MVA in ISR and identified an optimal cutoff value of 48 mm2. The multivariable logistic regression model confirmed that after adjusting for age, sex, and BMI, MVA ≤48 mm2 remained an independent predictor of ISR (adjusted OR = 7.464, 95% CI: 1.282–43.476, P = 0.025). This study provided the data associated with the incidence and risk factor of ISR after stenting in nonthrombotic IVCS patients. According to our results, 12.8% of diseased limbs presented ISR at a median time of 7.5 months after stenting. Multiple regression analyses suggested that MVA was an independent predictor of ISR after stenting in nonthrombotic IVCS. Diseased limbs with an MVA≤48 mm2 might need a more rigorous follow-up after stenting. With consideration of that ISR was more widely used in published reports and intimal hyperplasia might be inappropriate for research when no histopathological report was available for these patients, hence, ISR rather than intimal hyperplasia was adopted in this study.[2-4] In other researches,[2,4] the incidence of ISR varied from 27% to 77%, owing to different patients, detection methods and time to report. Neglen et al[2] showed that transfemoral venogram identified a cumulative incidence of 77%, 61%, and 15% at 42 months for ISR with any degree, ISR with diameter reduction >20%, and ISR with diameter reduction >50%, respectively. A recent study demonstrated that the incidence of ISR was 27% on post-surgery day 1 and increased to 74% at 3 months.[4] The incidence and severity of ISR reported by these studies were higher than our research. This might be related to the patients, who were included in those study, were different. This research only enrolled nonthrombotic IVCS, while both thrombotic and nonthrombotic IVCS were included in previous studies. Based on CT scan, the incidence of ISR in nonthrombotic IVCS was 12.8% at a median time of 7.5 months after stenting in this research. Obviously, this incidence is much higher than the Neglen et al's[5] report. This discrepancy could be mostly attributed to the different definitions of ISR. Neglen et al[5] reported a relatively low incidence of ISR based on severe stenosis (>50%), while we recorded ISR based on any degree stenosis in this research. Besides, the CT scan that was used in our study to identify ISR might be more sensitive than ultrasonic examination. Univariable analysis demonstrated five potential predictors (age, sex, BMI, MVA, and percent area stenosis) for ISR after stenting, but multivariable regression model recognized MVA as the only independent predictor of ISR. Taken together, all these data indicated a role of MVA in predicting the occurrence of ISR. This might be explained by that a smaller MVA indicated a more advanced stage of disease, thus leading to a higher risk of ISR after stenting. Besides, considering the post-stenting MVA was similar between the two groups, the vessel enlargement was much greater in the ISR group, leading to a stronger outward force by the stent, which would result in overreactive intimal hyperplasia. But further research was still needed to confirm the two assumptions mentioned above. Several limitations needed to be noticed about our study. Firstly, the retrospective nature of this research and the small sample size limited its generalizability, although the majority of included patients were from a prospectively registered cohort. Secondly, since only nonthrombotic IVCS was enrolled in this research, the findings of our study are limited to this subgroup of IVCS. Lastly, the follow-up period was relatively short, the long-term follow up research is needed to observe the association between ISR and the late outcomes of patients. In conclusion, ISR is not a rare condition after stenting in nonthrombotic IVCS patients. MVA is an independent predictor of ISR after stenting, and diseased limbs with an MVA ≤48 mm2 should be recommended with a restrictive follow-up. Conflicts of interest None.

Morphometric and Hemodynamic Analysis of the Compressed Iliac Vein.

To investigate the relationship between the morphological structure and hemodynamic properties of the compressed iliac vein and explore the reason for the formation of thrombosis in the compressed iliac vein. A total of 11 patients with iliac vein compression syndrome (IVCS) were included in this study, and their iliac veins were reconstructed in 3 dimensions (3D). The morphological structures of the iliac veins (confluence angle, degree of stenosis) were analyzed based on the 3D model. Variations in the hemodynamic properties of the iliac vein were investigated at 4 typical moments in one cardiac cycle, and the relationship between the different morphological configurations and the pressure difference was investigated. In the region of the compressed iliac vein, the blood flow velocity is accelerated and the pressure changes abruptly accompanied by the increase in pressure difference. Higher time averaged wall shear stress (TAWSS) and lower relative residence time (RRT) appeared in stenosis regions of compressed iliac vein, while TAWSS was low and RRT was large near the stenosis position. There was a strong positive correlation between the degree of stenosis and the pressure difference (r=0.894), and a positive correlation between the confluence angle of the iliac vein and the pressure difference (r=0.638). The morphological structure of the compressed iliac vein has an obvious influence on the hemodynamic surroundings; the pressure difference becomes larger when the degree of stenosis and the confluence angle increase. The iliac vein luminal areas with low TAWSS and high RRT near the compressed location can impede blood flow and lead to accumulation of blood components, which may increase the risk of thrombosis formation and should be fully considered in the treatment of IVCS.

The influencing mechanism of iliac vein stent implantation for hemodynamics at the bifurcation

In the intervention with stent implantation for iliac vein compression syndrome (IVCS), it remains unclear about the influencing mechanism of the structure and implantation position of the stent for the hemodynamics of the affected site. In this paper, an iliac vein model was established. Besides, the computational fluid dynamics (CFD) was utilized to analyze the time-averaged wall shear stress (TAWSS) and oscillatory shear index (OSI) in a sine period after stent implantation based on the three different implantation positions of two iliac vein stents (the left branch outlet, contralateral disturbed flow and main iliac vein). The influence of the structure and implantation position of the stent on blood flow was revealed. These findings were verified by the particle image velocimetry (PIV) experiment. The results indicated that the maximum blood flow velocity of the iliac vein decreased after the stent implantation. Among the three positions, the influence of stent implantation on the iliac vein blood flow was the least when the stent implantation was performed at the left branch outlet; the influence of stent implantation on the iliac vein blood flow was the greatest when the stent implantation was performed at the contralateral disturbed flow. Moreover, there was little influence of Venastent implantation on the blood flow. These results could provide a scientific foundation for implantation treatment and stent design related to IVCS.