Hrev_master Veins and Lymphatics 2017; volume 6:6855 [page 82] [Veins and Lymphatics 2017; 6:6855] Stenting for obstructive iliac vein lesions Arjun Jayaraj, Seshadri Raju The RANE Center for Venous & Lymphatic Diseases, St. Dominic Hospital, Jackson, MS, USA Abstract Endovenous stenting has supplanted open surgery as the treatment of choice for iliocaval obstruction. This review provides a brief overview of such obstructive pathol- ogy and an in-depth assessment of femoro- ilio-caval stenting. Introduction Obstructive iliac vein lesions can result from primary or non-thrombotic and sec- ondary or post-thrombotic pathology. The latter is responsible for a majority of all obstructive iliac vein lesions because of post thrombotic syndrome (PTS) develop- ment in 20 to 50% of patients who present with lower extremity deep venous thrombo- sis (DVT).1 Among non-thrombotic iliac vein lesions (NIVL), May-Thurner syn- drome (MTS)/iliac vein compression syn- drome (IVCS) is the most frequent etiology.2,3 While obstruction is seen prima- rily of the left common iliac vein, the right common iliac or either external iliac vein can also be involved in MTS/IVCS. Other less common causes of NIVL nclude retroperitoneal fibrosis; iatrogenic, blunt and penetrating trauma; congenital venous anomalies or benign/malignant tumors. Endovenous interventions have supplanted open surgery as the treatment of choice in patients with non-malignant obstructive iliac vein lesions. For patients with malig- nancy, venous stenting is used only when excision of the tumor/open reconstructive surgery is not possible and the goal of ther- apy is palliation. Adjunctive procedures such as femoral vein endophlebectomy/cre- ation of arteriovenous fistula are added to venous stenting to provide improved inflow. Diagnosis Clinical manifestations of chronic venous insufficiency arising from obstruc- tive lesions of the femoro-ilio-caval tract include swelling; varicosity; hyperpigmen- tation; venous claudication (pelvic, thigh or hip pain that develops after exercise); skin and subcutaneous inflammatory changes (eczema, lipodermatosclerosis, induration and venous ulcerations) of the affected limb. Of these, swelling has been noted to be the most common symptom followed by venous claudication in one review.4 In this study the incidence of active ulcers was approximately 19%. Diagnostic testing is focused on confirming the presence of an obstructive femoro-ilio-caval lesion and determining etiology. Additionally, inflow and outflow patterns should be ascertained. Such testing includes venous duplex scan- ning, which should be used as a screening tool and performed in all patients with clin- ical presentation suggestive of obstructive venous pathology. Duplex scanning helps define location, etiology (obstructive vs obstructive with concomitant valvular incompetence), and severity of the underly- ing problem. Air plethysmography can help evaluate global leg hemodynamics by measuring obstruction, reflux and calf pump function. Cross-sectional imaging including magnetic resonance (MR) venog- raphy and computed tomographic (CT) venography will identify obstructive pathol- ogy and provide sufficient information in most patients with regard to venous anato- my, collateral circulation and occlusion/stenosis. Ascending venography helps defines the site(s) of obstruction, col- lateral venous circulation and patterns of preferential flow. This is done by cannula- tion of the dorsal vein of the foot to assess the veins of the leg and through separate access of the common femoral vein to assess the ilio-caval system. Ambulatory venous pressure measurement by venous cannulation in the foot helps quantify venous hypertension. Intravascular ultra- sound (IVUS) is used to assess degree of iliac vein stenosis before stenting; to assess apposition of stent to vein wall post-stent- ing and to evaluate stent/flow status during follow-up of patients with recurrent symp- toms. IVUS is generally considered the gold standard from a diagnostic and therapeutic standpoint. Treatment Conservative management Initial management of femoro-ilio- caval obstruction is usually conservative, including frequent leg elevation, use of graduated compression stockings (30 to 40 mm Hg), and local wound care. Compression garments require strict com- pliance, which can be an issue due to a vari- ety of reasons, including warm weather and a sense of tightness of the limb. Benefits attributed to graduated compression stock- ings arise from their ability to impact venous hemodynamics, skin circulation, and calf muscle pump function. Patients with persistent disabling symptoms not responding to conservative measures should be considered for endovascular interven- tion. Endovascular treatment Femoro-ilio-caval stenting has become the primary treatment for obstructive venous pathology. Open approach is reserved for patients who are not candidates for or who have failed an endovascular approach. Endovascular intervention is usu- ally performed under general anesthesia (some interventionalists prefer moderate intravenous sedation) given the frequent severe intraoperative pain/discomfort asso- ciated with balloon angioplasty. Access to the mid-thigh femoral vein is obtained under ultrasound guidance. This allows angioplasty/stenting of the common femoral vein if needed, without being impeded by the sheath. A 0.035 Glide wire (Terumo Medical Corp, Somerset, NJ) is passed into the inferior vena cava and a short (10 cm) 11 Fr sheath is placed. An ascending venogram of the ilio-femoral segments and inferior vena cava is per- formed. In patients with renal dysfunction, the venogram is skipped. Intravascular ultrasound [Volcano, San Diego, CA] is then performed using the 0.035” catheter and planimetric measurements of the lumi- nal areas of the common femoral vein (CFV), external iliac vein (EIV) and com- mon iliac vein (CIV) are made. 125 mm2, 150 mm2 and 200 mm2 are used as normal luminal area cutoffs in the CFV, EIV and CIV respectively. Any decrease in luminal Correspondence: Arjun Jayaraj, The RANE Center, 971 Lakeland Drive, Suite #401, Jackson, MS 39216, USA. Tel.: +1.601.939.4230. E-mail: arjunjayaraj2015@gmail.com Key words: Iliac vein stenting; venous stents; obstructive iliac vein lesions; May Thurner syndrome; iliac vein compression syndrome. Received for publication: 18 June 2017. Revision received: 14 August 2017. Accepted for publication: 14 August 2017. This work is licensed under a Creative Commons Attribution 4.0 License (by-nc 4.0). ©Copyright A. Jayaraj and S. Raju, 2017 Licensee PAGEPress, Italy Veins and Lymphatics 2017; 6:6855 doi:10.4081/vl.2017.6855 Review areas below the reference values shown in Table 1 in a symptomatic patient is consid- ered abnormal, meriting angioplasty and stenting.5 It is important avoid using any particu- lar threshold value of stenosis for treatment because unlike the arterial system, elevated peripheral venous pressure is the driving force behind clinical symptoms/signs. In this regard, even a minor stenosis of around 30% or so can significantly elevate venous pressure in postthrombotic limbs. The basis of CVI is venous hypertension and the aim of stenting is to relieve the same. Predilation of the stenosis is performed using an 18×60 mm Atlas angioplasty bal- loon (Bard Peripheral Vascular, Tempe, AZ). Stenting is then carried out using 18- 20 mm Wallstents (Boston Scientific, Marlborough, MA) with landing zones determined by IVUS - defined bony land- marks. The proximal landing zone is typi- cally 1-2 cm above the iliac confluence that can be related to the corresponding verte- bral body (upper, middle or lower border). The distal landing zone is an area of ade- quate inflow in the CFV and can be related to a body landmark of the pubic ramus, femoral head or lesser trochanter. Attention must be paid to the vein at the level of the inguinal ligament since this is often an area of compression. Stenting across the inguinal ligament must be performed in these cases and can be done with good results (Figure 1).6 Given the relatively low radial strength of the Wallstent, a Gianturco Z stent (Cook Medical, Bloomington, Indiana) is used to provide additional strength across the con- fluence with an extension of the Gianturco stent beyond the Wallstent proximally into the IVC. The Gianturco Z stent should be oversized relative to the Wallstent with an overlap of the lower half of the Z stent with- in the Wallstent to prevent stent emboliza- tion. An overlap of 3 cm or so between each Wallstent in the stack is required to com- pensate for foreshortening during post-dila- tion. Post-dilation is performed using the 18×60 mm angioplasty balloon. Completion IVUS is performed to ensure adequacy of the luminal area. Any residual narrowing on IVUS interrogation is over- come by repeat dilation using sustained inflation or, if necessary, a larger caliber angioplasty balloon (20 mm). Completion venogram is then performed. The 11Fr sheath is subsequently withdrawn to just outside the vein and a Surgicel Fibrillar patch (Ethicon, Somerville, NJ) is intro- duced via the sheath to aid in local hemosta- sis. Manual pressure is maintained to com- plement the hemostatic effect. A retrograde access through the right internal jugular vein is also used if the obstruction cannot be crossed from the femoral access. Kurlinsky at al. reported their experience with stenting 91 post-thrombotic iliac or iliofemoral veins. Primary, primary assisted and sec- ondary patencies at 3 years were 71%, 90% and 95%, respectively.7 In the largest single institutional study, 6-year follow-up data of 982 stents placed for chronic nonmalignant obstructive lesions of the femoro-ilio-caval vein demonstrated primary, primary assist- ed and secondary patency rates of 79%, 100%, and 100% in nonthrombotic disease and 57%, 80%, and 86% in post-thrombotic disease, respectively.8 Chronic total occlusion Recanalization of chronic total occlu- sion (CTO) is most commonly done through the use of an 0.035” Glidecath (Terumo Medical Corp, Somerset, NJ) and 0.035” Glidewire. A mid-thigh femoral vein approach is satisfactory in most instances with a short entry to lesion length, allowing greater pushability of instruments. Access of the profunda femoris vein or the popliteal vein may sometimes be required depending on inflow. The internal jugular vein approach is sometimes necessary when the antegrade approach fails. A body floss tech- Table 1. Luminal area values. Vein Luminal area Diameter (mm2) (mm) CFV 125 12 EIV 150 14 CIV 200 16 CFV, common femoral vein; EIV, external iliac vein; CIV, common Figure 1. Stenting across the inguinal ligament using Gianturco Z stent/Wallstent combi- nation. Stenting can be carried out safely across the inguinal ligament without compromis- ing stent outcomes. Figure 2. Trabeculae in chronically throm- bosed vein segment. Successful recanaliza- tion requires localization and subsequent threading of guidewire through such tra- beculae. [Veins and Lymphatics 2017; 6:6855] [page 83] nique may be necessary occasionally as described by Kolbel and colleagues.9 Less commonly, other devices may be needed for recanalization of CTO lesions including Quick-Cross support catheter (Spectranetics Corp, Colorado Springs, CO) and the TriForce peripheral crossing set (Cook Medical, Bloomington, IN). The key is to gain entry into a trabecular channel, which then leads one all the way into a patent seg- ment (Figure 2). There is no role for subin- timal entry/angioplasty as is utilized to per- form recanalization of arterial segment CTOs. Once wire recanalization is attained, angioplasty is performed as previously out- lined. Sometimes, angioplasty with sequen- tially larger balloons may have to be employed due to inadequate purchase of the initial large caliber balloon. Rupture/hemor- rhage from this maneuver is extremely rare. Angioplasty is carried out caudal to cranial (femoral access) or cranial to caudal (jugu- lar access) as this facilitates easier retrieval of the angioplasty balloon should it disrupt. The likelihood of the latter happening is higher in CTO than in stenotic lesions. Use of stents, post-dilation, IVUS interrogation and venogram are all performed as previ- ously described. Fatima et al reported 90% two-year patency rate and 80% symptom- free survival in a series of 28 patients under- going inferior vena cava (IVC) stenting for occlusion (16)/high grade stenosis.12 Freedom from reintervention in this group, which included 13 patients with IVC filters at the 2-year mark, was 84%.10 Raju et al described their experience in 120 patients with chronic obstruction of the IVC and reported cumulative stent patency of 82% at 2 years.11 Relief of pain and swelling of 74% and 51% respectively was noted at 42 months follow-up. The cumulative rate of complete ulcer healing in this group at 2 years was 63%.11 More recently Murphy et al published outcomes following endovas- cular management of CTO of the inferior vena cava/iliac veins and noted primary, primary assisted, and secondary patency rates at 60 months of 52%, 85%, and 93%, respectively. The authors reported complete cumulative relief of pain and swelling in 66% and 41% respectively, with the venous clinical severity score improving from 8.4±5.1 (range, 4-27) prior to intervention to 3.9±3.2 (range, 0-14) post-intervention (P<0.001).12 Stenting across inferior vena cava filters Inferior vena cava filters can over time serve as a nidus for a fibrotic reaction that leads to IVC stenosis/occlusion. Trapped emboli may start the process in some instances. The occluded filter and IVC seg- ment must be recanalized to provide ade- quate outflow. This can be accomplished by removal of the filter if possible, or crushing the filter and stenting across it. 24 mm Wallstents are typically used in the IVC/across IVC filters and have had good results (Figure 3A-F). Patients need to be counseled about loss of filter protection for pulmonary embolism consequent to such procedures. In a review of 121 limbs that underwent stenting for postthrombotic ilio-caval occlusions, limbs stented for recanalized occlusions with (n=23) and without IVC filters (n=92) showed no difference in patency rates. Cumulative primary and secondary patency rates were 30% and 35% (P=0.97) and 71% and 73% (P=0.93) respectively. The authors conclude that the primary factor affecting stent patency in such patients was severity of postthrombotic disease and not presence of a filter.13 Bilateral iliocaval stenting There is a limited role for simultaneous bilateral femoro-ilio-caval stenting, except for bilateral recanalization procedures. Typically, the more affected leg is stented, giving adequate time for the less affected leg to improve from off-loading of cross collaterals. In patients with persistent symp- toms in the contralateral lower extremity, contralateral stenting can be pursued. In the presence of a prior Gianturco Z stent, the flowering technique is used wherein the cranial nylon suture of the new Gianturco Z stent is cut so as to allow the struts to flower out and allow it to mesh with the older con- tralateral Gianturco Z stent (Figure 4). If the contralateral stent is a Wallstent then a fenestrum needs to be created by wire access across the wall stent interstice and dilation of same using an 18x60 mm angio- plasty balloon. Stenting across this fen- estrum is accomplished using a combina- tion of Wallstent and Gianturco ‘crown’ as previously described. The wide struts of the Gianturco Z stent lining the fenestrum allow free flow in the contralateral stent across the fenestrum (Figure 5). The authors’ preference is to use a bilat- eral Wallstent/Gianturco Z stent combina- tion for management of the iliac confluence as opposed to the apposition, double barrel or fenestrum techniques. Raju et al reported 2-year cumulative primary and secondary patency of 69% and 93% respectively in 273 limbs intervened on by using the Z stent technique.14 Hybrid treatment Venous stents are combined with femoral vein endophlebectomy/patch angioplasty or arteriovenous fistula (AVF) creation or both to improve inflow into the stents. The stent is typically placed proxi- mal to the patch or can be extended into the patch. The common femoral or superficial femoral artery can be used for inflow to cre- ate the fistula, which is typically fashioned using a 4 to 6 mm externally supported PTFE graft. Acceptable outcomes following endophlebectomy and AVF creation have been reported.15-18 Anticoagulation For perioperative thromboprophylaxis, the authors use enoxaparin 40 mg given subcutaneously preoperatively, in addition to bivalrudin 75 mg given intravenously in the operating room prior to the start of the procedure. The authors use this combina- tion of direct and indirect thrombin inhibitors to reduce early stent complica- tions including thrombosis. Following ilio- caval stenting, in patients with thrombophil- ia/post-thrombotic syndrome therapeutic anticoagulation is continued. Those in whom thrombophilia workup is negative and who have non-thrombotic femoro-ilio- caval lesion, aspirin 81 mg with cilastazol 50 mg twice daily is typically used unless contraindicated. The latter is used for its suppressive effect on neointimal hyperpla- sia. Presence of significant in-stent resteno- sis, but with no symptom recurrence is an indication to switch to apixaban 2.5 mg on a twice-daily basis. Recurrence of symp- toms is an indication for repeat IVUS inter- rogation and possible angioplasty. Follow-up Venous duplex ultrasound is performed on post-operative day one to obtain baseline post-procedure metrics, including stent patency, and to assess stent compression and/or in-stent restenosis. These parameters are again evaluated by repeat duplex ultra- sound in addition to assessing symptom relief at clinic visits 2 weeks and 4 weeks post-procedure. Three to six monthly fol- low-up is required subsequently, which is gradually reduced to annual follow up depending on symptoms and status of stents. More frequent follow-up is typically required for PTS and recanalization patients. Review [page 84] [Veins and Lymphatics 2017; 6:6855] Review Figure 3. A-G) Recanalization - Iliocaval occlusion with IVC filter (A and B: right and left venogram demonstrating bilateral CTO with occluded IVC filter; C and D: IVC filter crush with 24 mm angioplasty balloon and subsequent stenting across filter; E: Stenting up to hepatic vein confluence to provide good outflow using Gianturco Z stent across renal veins; F: Iliocaval confluence stenting using Gianturco Z stent/Wall stent technique; G: completion venogram). [Veins and Lymphatics 2017; 6:6855] [page 85] Complications of iliac stenting and their management Femoro-ilio-caval stenting can be per- formed with minimal mortality and low morbidity. Reintervention is required at times. Raju et al. noted a reintervention rate of 13% following femoro-ilio-caval stent- ing in 1085 limbs. Median time to reinter- vention after the initial procedure was 15 months. Post-reintervention the group reported cumulative improvement in pain and swelling of 67% and 72%, respectively, at 18 months follow-up. Complete cumula- tive healing of venous dermatitis/ulcer at 12 months’ post-reintervention was 90%.19 Some of the potential complications that can be encountered are considered in the following paragraphs. Access site-related Such complications can be reduced by use of ultrasound guidance for access. Clinically significant hematoma/arterial injury/pseudoaneurysm/nerve injury is extremely rare (<0.1%). In most cases access site hematomas can be effectively managed with compression and delayed start of anticoagulation. Pseudoaneurysm, when indicated, is best managed by ultra- sound-guided thrombin injection. Patients who sustain nerve injuries attain symptom relief over time. However, counseling and setting realistic expectations are key. Vein injury/rupture Frank rupture of the intervened vein is uncommon due to relatively low pressure and significant periadventitial fibrosis around the vein. When rupture occurs use of a stent graft can help exclude the site of extravasation.20 In-stent restenosis In-stent restenosis (ISR) arises from either thrombus buildup or neointimal hyperplasia within the stent. The authors note an incidence of up to 25% in their experience. Patients presenting with recur- rence of symptoms require reintervention with angioplasty. This often involves use of an angioplasty balloon larger than the rated size of the stent used (e.g., for a 20 mm stent we can use a 22 mm angioplasty bal- loon). This is termed hyperdilation as opposed to isodilation, which is dilation with use of an angioplasty balloon of the same rated diameter as the stent. Therapeutic anticoagulation and use of cilastazol immediately after index stent pro- cedure may help reduce occurrence. Stent compression Stent compression occurs due to extrin- sic compression of the stent due to fibrotic tissue build up. This is a phenomenon unique to the venous system. Incidence is significantly lower than ISR, with treatment being hyperdilation in symptomatic patients. Larger caliber balloons may have to be used to overcome the stent compres- sion (22-24 mm) than in ISR. Stent thrombosis Layering of thrombus within the stent occurs can occur due to poor inflow, poor outflow or mechanical effects of an inade- quate stent stack with potential for stent thrombosis. The overall incidence of stent thrombosis is approximately 3.5% in the authors experience, with chronic thrombo- sis more common than acute.21 Contributing factors to an inadequate stent stack include use of undersized stent and understenting (not covering all areas of disease). Lack of perioperative use of anticoagulation/ antiplatelet agent(s) can also contribute to stent thrombosis. Restenting after fracturing the previously placed undersized stents with large caliber angioplasty balloons or exten- sion of stent stack proximally or distally as the case may be is required for undersized stent and under stenting, respectively. For acute/subacute occlusions treatment is with pharmacomechanical thrombectomy +/– balloon maceration (no pulmonary embolisms in the authors experience). For more chronic occlusions (CTO), recanaliza- tion can be pursued as described earlier. Acceptable results have been noted in both situations. Laser recanalization or radiofre- quency wire recanalization has also been used as a last resort in occluded stents with modest success. Review Figure 4. Bilateral stenting with use of Gianturco Z stents over- comes challenges arising from double barrel and fenestral tech- niques. Figure 5. Bilateral stenting using fenestrum creation through con- tralateral stent. Used when contralateral stent extends to ipsilateral caval wall and "standard" Gianturco Z stent/Wallstent combination is not an option. [page 86] [Veins and Lymphatics 2017; 6:6855] Review [Veins and Lymphatics 2017; 6:6855] [page 87] Contralateral iliac vein thrombosis This is a rare event occurring from jail- ing of contralateral common iliac vein by ipsilateral stent. It can be overcome by use of Wallstent-Gianturco Z stent (Boston Scientific, Marlborough, MA- Cook Medical, Bloomington, IN) combination and limiting extension into IVC. The latter technique reduces the risk of contralateral thrombosis by up to 85%.22 Stent migration Occurs due to the choke point effect of the iliac confluence. It is imperative to extend the stent stack proximal to the con- fluence to overcome this effect. Furthermore, use of the Gianturco Z stent (Cook Medical, Bloomington, IN) helps provide additional radial force and checks migration. Mortality Worldwide experience has proven venous stenting to be a low-risk procedure with negligible morbidity and mortality.23 References 1. Kahn SR, Comerota AJ, Cushman M, et al. The postthrombotic syndrome: evi- dence-based prevention, diagnosis, and treatment strategies: a scientific state- ment from the American Heart Association. Circulation 2014;130: 1636-61. 2. Raju S, Neglen P. 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