Stent Compression in Iliac Vein Compression Syndrome Associated with Acute Ilio-Femoral Deep Vein Thrombosis

Morphometric and Hemodynamic Analysis of the Compressed Iliac Vein

PURPOSE

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.

MATERIALS AND METHODS

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.

RESULTS

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).

CONCLUSION

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.

Pivotal Evaluation of Novel Dedicated Venous Stent for Iliofemoral Venous Obstruction: A Prospective Cohort Study

PURPOSE

The purpose was to evaluate the clinical outcomes of a dedicated venous stent with the tripartite composite segments for the treatment of iliofemoral venous obstruction (IVO) in a mixed cohort of nonthrombotic iliac vein lesion (NIVL) and post-thrombotic syndrome (PTS) over a period of 12 months.

METHODS

The Grency Trial is a prospective, multicenter, single-arm, open-label, pivotal study, which was conducted at 18 large tertiary hospitals in China from August 2019 to October 2020. A total of 133 hospitalized patients were screened and 110 patients with clinical, etiology, anatomical, and pathophysiology clinical class (CEAP) clinical grade C>3 and iliac vein stenosis >50% or occlusion, including 72 patients with NIVL and 38 patients with PTS, were implanted with Grency venous stents. Primary endpoint was stent patency at 12 months follow-up, and secondary outcomes were technical success; improvement in venous clinical severity score (VCSS) at 3, 6, and 12 month follow-up; and rates of clinical adverse events.

RESULTS

Among 110 patients who were implanted with Grency venous stents, 107 patients completed the 12 month follow-up. All 129 stents were successfully implanted in 110 limbs. Twelve-month primary patency rate was 94.39% [95% confidence interval [CI]=88.19%-97.91%] overall, and 100% [94.94%-100%] and 83.33% [67.19%-93.63%] in the NIVL and PTS subgroups, respectively. Venous clinical severity score after iliac vein stenting improved significantly up to 12 months follow-up. There were 3 early major adverse events (1 intracerebral hemorrhage and 2 stent thrombosis events related to anticoagulation therapy), and 7 late major adverse events (1 cardiovascular death, 1 intracranial hemorrhage with uncontrolled hypertension, and 5 in-stent restenosis cases without stent fractures or migration).

CONCLUSIONS

The Grency venous stent system appeared excellent preliminary safe and effective for IVO treatment. Further large-scale studies with longer-term follow-up are needed to evaluate long-term patency and durability of stent.

CLINICAL IMPACT

The design of venous stents for iliofemoral venous obstruction (IVO) must address engineering challenges distinct from those encountered in arterial stenting. The Grency venous stent, a nitinol self-expanding stent specifically tailored for IVO, features a composite structure designed to meet the stent requirements of various iliac vein segments. The Grency Trial is a prospective, multicenter, single-arm, open-label pivotal study aimed at evaluating the efficacy and safety of the Grency stent system. Following a 12-month follow-up period, the Grency venous stent system has demonstrated both safety and efficacy in treating iliofemoral venous outflow obstruction.

Venous stent patency is independent of total stented length in nonthrombotic iliac vein and post-thrombotic venous stenoses

OBJECTIVE

Venous stenting has become the preferred treatment of symptomatic outflow obstruction due to nonthrombotic iliac vein lesions (NIVLs) and post-thrombotic venous stenoses (PTs). A paucity of data exists regarding the effect of stent length on patency rates after intervention. We evaluated the association between stent length and patency in patients treated for iliofemoral venous outflow obstruction.

METHODS

The institutional review board approved the present study. A total of 161 patients had undergone venous stenting for NIVLs and thrombotic disease from January 2016 to April 2021. For thrombotic disease, patients with PTs and those with acute deep vein thrombosis (DVT) with underlying outflow obstruction were included. The patient characteristics evaluated included gender, age, body mass index, diagnosed thrombophilia, a history of venous thromboembolism, and CEAP (clinical, etiologic, anatomic, pathophysiologic) score. All the patients had undergone multiplanar venography and intravascular ultrasound during the index procedure. The intravascular ultrasound findings were used to determine the diameter and length of the implanted stents. The patients were placed into two groups, those with stented lengths ≤100 mm and those with stented lengths >100 mm. The primary end point was stent patency between the two groups using duplex ultrasound at 6 months.

RESULTS

A total of 108 patients (58.3% female) had had 6-month duplex ultrasound scans available for review. Their mean age was 55.6 ± 17.2 years. The mean body mass index was 31.7 ± 6.9 kg/m². Overall, the 6-month patency was 89.9%. Of the 108 patients, 56 (51.9%) had had a total stented length of ≤100 mm with a 6-month patency of 92.9%. The remaining 52 patients (48.1%) had had a total stented length >100 mm with a 6-month patency of 86.5%. The rate of patency did not differ significantly between the two groups (P = .222). Stent patency at 6 months for patients with NIVLs was 98% (40 of 41). Stent patency for patients with PTs was 84% (32 of 38). Patency for patients with acute DVT who had undergone stenting after thrombectomy was 86% (25 of 29). Overall, 10 patients with thrombotic disease, including PT and acute DVT, had developed stent thrombosis. The total stented length was not predictive of the loss of patency.

CONCLUSIONS

These findings suggest that the length of stent coverage does not confer an increased likelihood of stent thrombosis for patients with iliofemoral venous obstruction. Interventionalists should treat the affected venous segments identified on intravascular ultrasound and effectively stent from normal to normal venous areas, regardless of the stent length required. These results suggest that the total stented length is not a risk factor for stent thrombosis for both NIVL and thrombotic iliofemoral venous lesions.

Current Status and Prospect of Stent Placement for May-Thurner Syndrome

Stent implantation has been proven to be safe and has become the first-line intervention for May-Thurner syndrome (MTS), with satisfactory mid-term patency rates and clinical outcomes. Recent research has demonstrated that catheter-directed thrombolysis is the preferred strategy when MTS is combined with deep vein thrombosis after self-expanding stent placement. However, the stent used for the venous system was developed based on the experience obtained in the treatment of arterial disease. Consequently, relatively common corresponding complications may come along later, which include stent displacement, deformation, and obstruction. Different measures such as adopting a stent with a larger diameter, improving stent flexibility, and increasing stent strength have been employed in order to prevent these complications. The ideal venous stent is presently being evaluated and will be introduced in detail in this review.

The effect of stent compression on in-stent restenosis and clinical outcomes in iliac vein compression syndrome

Background

To evaluate the effect of stent compression on in-stent restenosis (ISR) and clinical outcomes in patients with iliac vein compression syndrome (IVCS) after iliac vein stenting.

Methods

Fifty patients with IVCS treated with iliac vein stenting (Smart Control, Cordis, USA) between March 2017 and October 2018 were consecutively enrolled in this study. Computed tomography venography (CTV) was performed to assess stent compression and ISR. Based on the degree of stent compression, patients were allocated to a significant stent compression (SSC) group and an insignificant stent compression (ISC) group. The incidence of ISR was analyzed between the SSC and ISC groups. Patients' venous clinical severity scores (VCSSs) and responses to the chronic venous insufficiency questionnaire (CIVIQ) one year after stenting were compared between the two groups to evaluate the clinical improvement of venous insufficiency.

Results

In total, 34% of patients had SSC. There were significant differences in the incidence of ISR (52.9% vs. 21.2%, P=0.023), and in each group, there was one case of stent occlusion (5.88% vs. 3.03%, P=0.999). Patients in the SSC group had a higher VCSS score (8.41±5.92 vs. 3.15±2.87, P=0.04) and a lower CIVIQ score (83.35±8.86 vs. 92.21±4.32, P=0.001).

Conclusions

SSC has a significant effect on the incidence of ISR and the clinical outcomes of venous insufficiency. Thus, a dedicated iliac venous stent with sufficient radial resistive force, crush resistance, and outward radial force is needed to prevent the occurrence of stent compression.

Doppler ultrasound and contrast-enhanced ultrasound in detection of stent stenosis after iliac vein stenting

Background

To compare the diagnostic accuracy of Doppler ultrasound (DUS) with contrast-enhanced ultrasound (CEUS) for detection of iliac vein stent stenosis using multidetector computed tomography venography (MDCTV) as the reference method.

Methods

Patients with iliac vein obstructive disease treated with nitinol stents (Smart Control, Cordis, USA) between January 2016 and December 2017 were consecutively included in this study. DUS, CEUS, and MDCTV were carried out in all patients within one week of each other at 1 year post stenting to investigate the presence of stent compression and in-stent restenosis (ISR).

Results

The study included 139 patients (87 females; mean age 58 ± 15 years). For detecting stent compression, the kappa coefficient between the ultrasound modality of gray-scale imaging and MDCTV was 0.901, indicating very good agreement between these two modalities. ISR was detected in 50, 61, and 65 patients by DUS, CEUS, and MDCTV, respectively. DUS and CEUS (kappa = 0.449) and DUS and MDCTV (kappa = 0.516) had moderate agreement for ISR diagnosis, while for which CEUS and MDCTV (kappa 0.884) had very good agreement. The sensitivity and specificity of DUS and CEUS for diagnosing ISR were 63.1% and 90.8%, 87.8% and 97.3%, respectively.

Conclusions

CEUS is probably superior to DUS in terms of diagnostic accuracy for the follow-up of patients with iliac vein stent stenosis.

Device profile of the Vici venous stent for chronic iliofemoral venous obstruction recanalization: overview of its safety and efficacy

Introduction: Endovenous stenting is being increasingly used for the management of iliofemoral venous outflow obstruction due to thrombotic or non-thrombotic iliac vein lesions (NIVL). Dedicated venous stents have replaced re-purposed arterial stents but there are limited data on their relative safety and efficacy.Areas covered: This review looks at the available literature on the safety and efficacy of the Veniti Vici Venous stent (Boston Scientific), a specific venous stent, and compares its outcomes with the other venous stents that are currently available. Reported outcomes include patency, clinical efficacy, and the number of adverse events.Expert opinion: The initial clinical trials of the Vici venous stent have shown both good clinical and safety outcomes at 12-24 months follow-up. Longer follow-up data are pending and further trials comparing available stents are required. Current evidence supports its use in the management of deep venous reconstruction, especially in occlusive post-thrombotic disease. Patients should, however, be made aware of the paucity of long-term data and the need for monitoring within a dedicated surveillance program following stent placement.

Investigation of adverse events associated with an off-label use of arterial stents and CE-marked iliac vein stents in the iliac vein: insights into developing a better iliac vein stent

We analyzed the adverse events associated with an off-label use of arterial stents and CE-marked iliac vein stents for the treatment of iliac venous thromboembolism and investigated their relationships with the anatomical features of the iliac vein, to gain insights into the development of a better iliac vein stent. Reports of adverse events following the use of stents in the iliac vein were retrieved from the Manufacturer and User Facility Device Experience (MAUDE) database that contain suspected device-associated complications reported to the Food and Drug Administration. Data from 2006 to 2016 were investigated. The literature analysis was also conducted using PubMed, Cochrane Library, EMBASE, and Web of Science focusing on English articles published up to 4 October 2016. The analysis of 88 adverse events from the MAUDE database and 182 articles from the literature revealed that a higher number of adverse events had been reported following the use of arterial stents in the iliac vein compared to CE-marked iliac vein stents. While stent migration and shortening were reported only for the arterial stents, stent fracture and compression occurred regardless of the stent type, even though a vein does not pulsate. A study of the anatomical features of the iliac vein implies that bending, compression, and kink loads are applied to the iliac vein stents in vivo. For designing, developing, and pre-clinical testing of stents intended for use in the iliac vein, the above mechanical load environments induced by the anatomical features should be considered.