|Year : 2021 | Volume
| Issue : 5 | Page : 11-17
Contralateral deep-vein thrombosis in lliac vein stenting – Incidence, etiology, and prevention
Venkataprasanna K Shanmugham, Venkatesh Bollineny, Prasenjit Sutradhar, Robbie K George
Department of Vascular and Endovascular Surgery, Narayana Institute of Vascular Sciences, Narayana Hrudayalaya, Bengaluru, Karnataka, India
|Date of Submission||17-May-2021|
|Date of Acceptance||24-May-2021|
|Date of Web Publication||30-Aug-2021|
Robbie K George
Department of Vascular and Endovascular Surgery, Narayana Institute of Vascular Sciences, Narayana Hrudayalaya, Bengaluru, Karnataka
Source of Support: None, Conflict of Interest: None
Iliocaval venous obstruction is a significant contributor to venous hypertension. Recanalization and stenting of chronic deep venous obstructions are minimally invasive and have been proven to be safe and effective with low complication rates over the past few decades. Common iliac vein (CIV) stents are usually extended into the inferior vena cava (IVC) to some extent to ensure adequately that key areas of stenosis are adequately treated. This may lead to contralateral CIV jailing and increase the risk of contralateral deep-vein thrombosis (DVT). The reported incidence of contralateral DVT after CIV stent placement from different studies varies from 1% to 15.6%. The predicted risk factors are noncompliance with anticoagulation, underestimation of the postthrombotic venous disease, preexisting IVC filter, incorrect stent placement, preexisting contralateral internal iliac vein thrombosis, malignancy, and thrombophilia. Literature suggests that the use of intravascular ultrasound, newer dedicated stents, and Z-stent modification reduces the incidence of contralateral DVT. Precise stent deployment technique and proper attention to other hematological risk factors are the key to preventing this complication. This article will review the incidence, mechanism, risk factors, and technical aspects of how to avoid this unfortunate complication. We will also review the newer dedicated venous stents.
Keywords: Deep vein thrombosis, iliac vein stenting, iliac vein thrombosis, May-Thurner syndrome, postthrombotic syndrome
|How to cite this article:|
Shanmugham VK, Bollineny V, Sutradhar P, George RK. Contralateral deep-vein thrombosis in lliac vein stenting – Incidence, etiology, and prevention. Indian J Vasc Endovasc Surg 2021;8, Suppl S1:11-7
|How to cite this URL:|
Shanmugham VK, Bollineny V, Sutradhar P, George RK. Contralateral deep-vein thrombosis in lliac vein stenting – Incidence, etiology, and prevention. Indian J Vasc Endovasc Surg [serial online] 2021 [cited 2022 May 24];8, Suppl S1:11-7. Available from: https://www.indjvascsurg.org/text.asp?2021/8/5/11/324946
| Introduction|| |
Chronic venous obstruction of iliac veins and inferior vena cava (IVC) remains a significant cause of morbidity for many adults worldwide. Patients with iliocaval obstruction often present with life-limiting occlusive symptoms such as swelling, pain, stasis ulcers, or in rare instances, phlegmasia which are secondary to recurrent lower extremity deep venous thrombosis. Even though patients with chronic venous obstruction have traditionally been treated with compression and limb elevation, venous stenting has changed the treatment paradigm completely. Iliocaval venous reconstruction by recanalization, angioplasty, stenting, and restoration of in-line flow provides symptomatic relief with minimal morbidity. Although level I evidence is lacking, clinical experience suggests that venous stenosis of lower extremities do not respond to angioplasty alone. Therefore, endovascular stenting has become the first-line treatment for patients with symptomatic iliofemoral stenosis or occlusion.
The proximal common iliac vein (CIV) is the most common site of venous stenting. It is the typical location for dense and fibrotic lesions that develop at the site of anatomical choke points. Previous research by Neglen and Raju had shown that extent of venous involvement is significantly more than is visible on venography, as a consequence of which they have recommended long stents that extend well beyond the visualized lesion. In iliocaval confluence stenting, the stent will project into the IVC and potentially “jail” the contralateral venous outflow. This extension might increase the risk of thrombosis in the normal contralateral iliofemoral venous outflow. The aim of this article is to review the incidence of contralateral deep vein thrombosis (DVT) in patients who undergo ipsilateral iliocaval stenting and what preventive measures or procedural modifications are being done worldwide to prevent this occurrence.
| Iliocaval Obstruction|| |
The two major types of iliocaval venous obstruction are nonthrombotic iliac vein lesions or MayThurner syndrome and postthrombotic iliac vein stenosis resulting from a prior episode of DVT. In a cadaveric study investigating the aortoiliac arterial and venous bifurcation anatomy, May and Thurner reported compression of the left iliac vein against the fifth lumbar vertebra by the right iliac artery in 22% of the cases. Variants of this syndrome resulting in compression of the right iliac vein or distal vena cava by the aortic bifurcation have also been described. Iliofemoral venous thrombosis due to compression occurs in many asymptomatic patients as well.
| Ilio Caval Stenting|| |
Venous stenting is the preferred treatment in iliofemoral stenosis and chronic total occlusions. Iliac vein stenting is proven to be safe and effective, in the vast majority of cases. The technique is relatively easier to learn and use compared to open surgery and is potentially beneficial to a large proportion of patients. Open surgeries such as the venovenous bypasses which were previously the standard for chronic iliocaval occlusions are now reserved for multiple failed endovascular attempts or salvage of stent failures.
Venography has limitations in the visualization of all lesions and currently, the use of intravascular ultrasound (IVUS) is preferred and almost deemed essential for deep venous interventions. The venous system has completely different hemodynamics and anatomical requirements when compared to arterial. Despite this, for many years arterial stents were used for the management of venous lesions. Dedicated venous stents have been available for some years and [Table 1] shows various available venous stent devices.
| Contralateral Deep Vein Thrombosis|| |
Extensive work reported by Raju and Neglen had identified nonthrombotic iliac vein lesions (NIVL) as a significant etiological factor in chronic venous insufficiency. They advocated stenting iliac veins with the Wallstent. At the time, it was probably the only available self-expanding stent in the size range of larger than 14 mm that would be required for the iliocaval system. Accurate stenting of the proximal CIV was always challenging for two primary reasons – difficulty in accurately locating the extent of the lesion and its relation to iliac vein confluence on venography. This was compounded by the limitations of the Wallstent. The design of the stent is such that it has maximum strength in the central section and is weakest at the edges. Hence, it was necessary to position the stent extending well into IVC to avoid collapse of the cephalad portion of the stent with or without downward displacement. It was thought that there would be no reduction in venous drainage of the contralateral vein by this strategy and certainly, none was observed in the early period.
| Incidence of Contralateral Deep Vein Thrombosis|| |
Neglen and Raju in 2007 did a retrospective analysis on the incidence of contralateral DVT and found 1% of 982 patients to have contralateral DVT over a mean follow-up period of 22 months. Out of 1%, one-third were stented for NIVL indication and the rest were thrombotic obstructions. Considering the low incidence of contralateral DVT reported it was being overlooked for a period of time. Later, in 2014, Caliste et al. retrospectively looked into 5 years of data and identified an incidence of 9.7% new thrombosis in the nonstented contralateral iliofemoral veins. Among them, 2.4% were “true” contralateral DVT while the remainder were thought to be due to prior extension of the disease into IVC or noncompliance with anticoagulation.
In 2017, Le et al. also reported a 9% incidence of contralateral DVT over a median follow-up period of 40 months (range: 6–98 months) in patients who received stents for May-Thurner syndrome. Among them, 80% had their initial CIV stents extended into IVC and the rest had stent covering only up to confluence.
Murphy et al. did a retrospective comparative analysis among patients who underwent iliac venous stenting (10 years period) with caval extension of Wallstent and reported a cumulative freedom from contralateral DVT of 90% at 5 years follow-up.
Khairy et al. in their study from 2017 reported a 2.7% incidence of developing contralateral iliac DVT with ipsilateral iliac stenting. They noted that this occurred only with complete coverage of the contralateral CIV. The cumulative incidence of contralateral DVT was 4% at the end of 6 years. The median time to DVT was 225 days including three of them who developed in <30 days.
Gamas et al. did a systematic review on published articles reporting contralateral DVT between 2007 and 2019 and identified an overall incidence varying between 0% and 15.6% (2.3% in the earliest compared series) for a mean patient follow-up period (6–62 months). All the studies had heterogeneous postinterventional and follow-up anticoagulation regimens. The decision on anticoagulation and treatment duration was based on comorbidities, hypercoagulable states, pyruvoyltetrahydropterin synthase (PTS), and history of recurrent DVT. Patients with NIVL were anticoagulated for a period of three to 6 months or received no anticoagulation. PTS patients were anticoagulated for longer periods. They concluded that both stenting technique and poststenting antithrombotic regimes had an impact on the incidence of contralateral DVT.
| Etiology of Contralateral Deep Vein Thrombosis|| |
The vast majority of contralateral DVT has been reported with the use of Wallstent. This is a consequence of design, stent limitations, and the fact that it was the most commonly used stent for decades. Venous stenting started in the early 1990s. At that time, the Wallstent endoprosthesis (Boston Scientific Corporation) was the only self-expanding stent available in diameters and lengths suitable to the iliocaval system. The Wallstent is a stainless steel compressed spring-like stent that was designed for use in arterial, biliary, and bronchial systems. Arterial stents were often used due to the unavailability of stents designed for venous anatomy. They are stiffer and cannot conform to the venous anatomy resulting in potential areas of kinks and chronic intimal damage that can promote thrombosis.
The Wallstent excels and rarely fractures or fails primarily through the main body of the stent. The stent handles well the curves of the pelvic veins, crosses inguinal ligament with ease, and provides strength through both radial force and compression resistance. Until recently, it was the only available stent in diameters large enough to replicate the size of noncompressed, nondiseased iliac veins, typically ranging from 14 mm to 18 mm.
Although the design of the Wallstent has proven advantageous, it did have two critical shortcomings. First, stent edges are weaker than the main body making them more prone to collapse or occlude if landed within the diseased or externally compressed vein. This presents a major technical limitation when treating the cranial most portion of CIV, which is often the site of stenosis. When stenting this lesion, it positions the weakest portion of the stent at the point of maximum compression and eventually results in stent collapse, coning, or downward displacement if left unsupported as shown in [Figure 1]. To overcome this shortcoming, it was recommended to position the Wallstent in such a way that the cranial edge of the stent landed within the IVC so that the lesion was covered with the stronger main body of the stent as shown in [Figure 2].
|Figure 1: (a) Wallstents landed at iliac confluence are subjected to stent collapse due to lack of radial forces at stent ends (intravascular ultrasound demonstration); (b) Occlusion of Wallstent secondary to collapse and coning of the proximal stent|
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|Figure 2: Poststenting venogram showing the Wallstent placed well into the inferior vena cava to prevent coning and retrograde migration|
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Another disadvantage of the Wallstent is the challenge of accurate positioning. This is a consequence of its braided matrix design. The stent has great flexibility through tortuous curves and across the inguinal ligament. However, it shortens significantly, in an unpredictable fashion, as in expand during deployment. This worsens with post dilatation. Precise deployment of the stent edge is still a difficult task even in experienced hands.
Khairy et al. found that contralateral DVT was dependent on the extent of coverage of the contralateral orifice. Accordingly, IVC extension of stents was classified into three categories as shown in [Figure 3]:
|Figure 3: A diagram showing the three categories of inferior vena cava stent extension: (1) complete, (2) partial, (3) flush with the iliocaval confluence|
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- Complete (>20 mm), from the confluence to the tip of the stent protrusion into the IVC reaching the contralateral IVC wall with near 100% jailing
- Partial (10–20 mm), the degree of coverage depends upon the angle of the confluence and the vessel size
- Flush with the iliocaval confluence, with nil contralateral CIV coverage.
In their report, among the 86% of patients who had near 100% jailing of the contralateral iliac vein (Category I), 2.7% developed DVT on the right (contralateral) side and they were the only patients who developed contralateral DVT in the whole study population.
Hence, they concluded that stenting across the iliocaval confluence can be safely done in the majority of the patients with thrombotic obstruction followed by therapeutic anticoagulation provided the other factors are kept in mind. When the stent is extended into the IVC, contralateral iliac blood flow is through the closed cell stent interstices. These eventually develop a thin neo-intimal layer over time and limit the flow of blood as depicted in [Figure 4]- an intraoperative image reported by Gloviczki et al. This is something similar to the gradual IVC filter occlusion and is more common with patients who are not on anticoagulation.
|Figure 4: Intraoperative photograph showing the pseudointimal flap formed at the right common iliac vein around stent wires and excised flap with thrombus shown in the right-side panel|
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As the Wallstent suffers from significant foreshortening, precise positioning of the distal most end is sometimes difficult. Hence skip lesions might occur requiring multiple overlapping stents. Hence, previous studies advice multiple stents with adequate overlap to avoid treatment incompleteness. This resulted in making the stented segment more rigid, and also the stent needs placement far into the IVC to avoid retrograde migration which eventually increases the jailing of opposite CIV and potentiates thrombosis.
Several factors other than stent technique also contribute to the development of contralateral DVT. Significant factors associated with an increased risk of contralateral DVT are the presence of postthrombotic venous disease and/or its underestimation, presence of an IVC filter, noncompliance with anticoagulation, and failure of venous stenting technology or its application. Other factors are treatment indication of acute left iliac vein DVT, preexisting contralateral internal iliac vein (IIV) thrombosis, malignancy, and documented thrombophilia.
| Techniques of Prevention|| |
Z stent modification
Despite the shortcomings of the Wallstent, it still remains a sturdy and reliable stent for treating iliocaval outflow obstructions, especially when used with the Z stent combination. The Z stent was originally designed as a tracheobronchial stent but later had found use in treating chronic venous obstructions, initially in superior vena cava and then in the IVC., The Z stent has giant interstices but is very stiff, hence it is used to support the proximal CIV and extend into IVC where its wide open interstices will not limit contralateral iliac vein flow. The use of the Zstent technique was first described in 2014.
The proper technique involves placing the Wallstent well within the iliac vein right up to but not into IVC. This is followed by reinforcement with the Z stent by positioning 75% of the stent within the previously placed Wallstent; which leaves approximately one quarter of the Z stent's length protruding into IVC as shown in [Figure 5]. This prevents collapse of the cranial edge of the Wallstent and also reduces the consequences of contralateral DVT over time.
|Figure 5: Iliac vein stenting using a Wallstent and a Z stent extension|
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Murphy et al. compared the incidence of contralateral DVT among those with caval extension of Wallstent and those with Z stent extensions. They concluded that the cumulative freedom from contralateral DVT was 99% and 90% in the Z stent and Wallstent groups, respectively (P < 0.001) on 5 years follow-up. However, patients who developed DVT contralateral to a Z stent had a prior high placement of the Wallstent across the confluence. Hence, no patient with proper Z stent technique had a contralateral DVT.
The use of this technique facilitates bilateral CIV stenting by allowing the stents to mesh together without luminal compromise, effectively creating the caval confluence.
| Accurate Positioning of the Stent|| |
The optimal landing position of a venous stent is a debatable topic. IVUS provides excellent diagnostic and anatomical information compared to planar venography as demonstrated in the venography versus IVUS for diagnosing and treating iliofemoral vein obstruction (VIDIO) trial, and also aids precise stent placement. The major advantages of IVUS-guided intervention are precise identification of the diseased segment and positioning of stents at iliac vein confluence and in cases of extensive iliac vein thrombosis, confirmation of the course of the recanalizing guidewire within the iliac vein remnant alongside the iliac arteries. However, high cost and availability limit operators' access to this device.
Till very recent systematic reviews and meta-analyses have demonstrated the majority of operators following the Neglen and Raju technique, by landing their stents at a variable distance into the IVC.
Fluoroscopic techniques using bony landmarks have been well described and documented in many endovascular procedures. Bajwa et al. reported a landing technique using fluoroscopic bony landmarks for iliocaval stenting. The aim is to cross the culprit lesion and keep minimal stent extension into the IVC in patients with MTS. They carried out a series of stentings and checked with pre- and post-procedure CT to identify the correlation between vascular structures and bony landmarks. They found that the position of important vascular structures lies in predictable position relative to the bony landmarks and allows accurate deployment of dedicated venous stents using AP fluoroscopy with the right lower corner of the cephalic venous stent beyond the point of maximal compression by RCIA and preserving adequate right CIV drainage. We refer the readers to the original article, but a brief summary of the key steps is provided below.
After standard access and venogram/predilatation, the image intensifier is rotated into a strict anteroposterior projection such that the image was centered over the lumbar vertebra spinous process (SP) and each pedicle was equidistant from the SP. The left goal posts were defined as the SP and the right pedicle, the right goalpost. The proximal radiopaque marker of the stent delivery system was positioned immediately lateral (right lateral if supine or left lateral if prone) to the SP as shown in [Figure 6]. The right lower corner of the cephalic end of the venous stent was deployed lateral to the appropriate SP of the lumbar vertebra, but not as far as the lateral margin of the right pedicle of the same lumbar vertebra as depicted in [Figure 7] and [Figure 8].
|Figure 6: Present deployment in PRONE antero-posterior fluoroscopy. The proximal radiopaque marker of the stent delivery system|
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|Figure 7: (a) Successful poststent deployment in supine antero-posterior fluoroscopy. The lower corner of the cephalic stent (black arrow) is between the SP and right pedicle right lateral border or “goal posts.” (b) Follow-up coronal computed tomography venogram. Vici venous stent system (Boston scientific) with a 16-mm diameter and 120-mm length. The right lower corner of the cephalic stent (black arrow) is beyond the proximal right common iliac artery (black dashed arrow) but is not touching the contralateral inferior vena cava wall (white arrow)|
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|Figure 8: Antero-posterior schematic of a lumbar vertebra. The mean position of the right common iliac artery relative to the bony landmarks. CIA: Common iliac artery|
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Using this technique of landing, they had overall primary patency of 88% at 1 year and only 2 out of 112 patients had contralateral DVTs – one with factor V mutation and another with colorectal cancer and retroperitoneal and iliac lymphadenopathy. The only limitation they observed was alternative spine anatomy (scoliosis or pedicle variants or congenitally absent pedicle).
| Dedicated Venous Stents|| |
Newer “dedicated venous stent” designs promise a potential change in the perioperative technical and long-term clinical success., These stents have been designed to cope with the unique needs of the venous system. These include flexibility, tortuosity, resistive force, and accuracy of deployment. The most recently US-FDA-approved dedicated venous stents are laser-cut nitinol stents, with connecting rings with the close cell design and tiny connections to maintain flexibility. They are also available in lengths and diameters suited to the venous systems.
A specific mention is made of the Sinus-Obliquus stent, which is designed with an oblique “mouth” specifically for deployment at the IVC confluence without causing jailing of the contralateral IVC. The stent has a hybrid design with proximal open and distal closed-cell design sections to deal with the differing needs of the iliac system. However, long-term patency and follow-up for complications related to the use of this hybrid dedicated venous stents is being done by Nils Kucher et al. as the (Treatment of Postthrombotic syndrome with the Oblique Stent) study. They are following up patients who underwent iliac stenting with the sinus-Obliquus device for up to 2 years and the estimated primary completion is by November 2020.
| Conclusion|| |
Iliocaval stent reconstruction is often a technically successful procedure for life-limiting iliocaval thrombosis in experienced hands that has favorable clinical outcomes, stent patency, and low complication rates. While venous stenting is the first line of treatment for chronic obstructive lesions, the incidence of contralateral DVT due to iliac vein jailing is not negligible and should not be overlooked. It often occurs late during long-term follow-up and is associated with overextension of the CIV stent into the IVC. Other contributory factors such as contralateral IIV thrombosis, preexisting IVC filters, malignancy, extrinsic compression, and anticoagulation noncompliance should be considered. The use of the Z stent modification, newer dedicated stents, and IVUS may well reduce the incidence of contralateral DVT but careful attention to the precise deployment of the stent and use of all possible methods for the same with appropriate management of other hematological risk factors is essential to prevent this complication.
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8]