Two Year Outcome After Chronic Iliac Vein Occlusion ...

Eur J Vasc Endovasc Surg (2018)

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Two Year Outcome After Chronic Iliac Vein Occlusion Recanalisation Using the Vici Venous StentÒ Stephen Black a,*, Adam Gwozdz a, Narayan Karunanithy b, Justinas Silickas a, Karen Breen c, Beverley Hunt c, Alberto Smith a, Ander Cohen c, Prakash Saha a a

Academic Department of Vascular Surgery, Guy’s and St. Thomas’ NHS Trust, King’s College London, London, UK Department of Interventional Radiology, Guy’s and St. Thomas’ NHS Trust, London, UK c Thrombosis and Haemophilia Centre, Guy’s and St. Thomas’ NHS Trust, London, UK b

WHAT THIS PAPER ADDS This is the first report of two year outcomes with a new dedicated venous stent: the closed cell designed Vici Venous StentÒ. The stents were placed in patients with chronic post-thrombotic iliofemoral occlusion, with frequent stent placement beneath the inguinal ligament. Good secondary patency rates were observed over a 24 month follow up, although a more formal assessment to grade venous inflow may improve stenting outcomes in this region. While reduction in severity of post-thrombotic syndrome was most marked in the first six months after stenting, sustained clinical benefit was observed over 24 months. No significant differences were found in clinical and stent outcomes in patients with stenting terminating above or below the inguinal ligament, suggesting that stenting across the inguinal ligament is not a significant factor in patency and clinical outcomes. Objective/background: The aim was to assess two year outcomes with placement of the Vici Venous StentÒ in patients with chronic iliofemoral venous occlusions (complete blockage). Methods: This was a retrospective single centre study comprising patients treated with the Vici Venous Stent for venographically verified iliofemoral venous occlusion and post-thrombotic syndrome (Villalta score 5 points) at least 12 months after acute deep vein thrombosis. Venography and intravascular ultrasound were used perioperatively; duplex ultrasound was used to assess stent patency during follow up. Results: Eighty-eight patients (101 limbs) had stent placement between March 2014 and October 2016. Median pre-treatment Villalta score was 14 (range 5e33). Stenting extended across the inguinal ligament in 63 limbs (62%) in order to land in a healthy venous segment. Six patients (7%) required endophlebectomy and fistula creation. Median imaging follow up was 21 months (range 0e41 months). Primary, assisted primary and secondary patency rates at one year were 59%, 78%, and 87%, respectively, and two years 51%, 73%, and 82%, respectively. Forty-three limbs (43%) had re-intervention (lysis, venoplasty, and/or placement of stent) during follow up; median time to re-intervention was 32 days (range 0e520 days). At 24 months, 37 of 53 limbs (70%) with available Villalta assessment showed clinically significant improvement (>30% reduction of baseline score). Villalta scores at the 6, 12, and 24 month clinical follow up were significantly lower than before stenting (p < .001, all time points). In a subset analyses of limbs with stenting terminating above and below the inguinal ligament, secondary cumulative patency rates at 24 months were 90% and 79%, respectively; clinical outcome showed 58% vs. 73% of limbs with clinically significant improvement, respectively. There was no statistically significant difference in patency or clinical outcomes. Conclusion: The Vici Venous Stent is associated with a good secondary patency rate and durable and substantial symptomatic resolution in patients with chronic post-thrombotic occlusions, regardless of whether stents extended beneath the inguinal ligament. Ó 2018 Published by Elsevier B.V. on behalf of European Society for Vascular Surgery. Article history: Received 21 January 2018, Accepted 14 July 2018, Available online XXX Keywords: Chronic occlusion, Inguinal ligament, Post-thrombotic syndrome, Venous stent

* Corresponding author. Academic Department of Surgery, Cardiovascular Division, King’s College London, 1st Floor North Wing, St Thomas’ Hospital, Westminster Bridge Road, London SE1 7EH, UK. E-mail address: [email protected] (Stephen Black). 1078-5884/Ó 2018 Published by Elsevier B.V. on behalf of European Society for Vascular Surgery. https://doi.org/10.1016/j.ejvs.2018.07.014

INTRODUCTION Endovascular stent placement has supplanted venous bypass as the “method of choice” to treat femoro-ilio-caval venous outflow obstruction in patients with clinically significant chronic venous disease, with open surgery now considered a last resort after a failed stent procedure. Until

Please cite this article in press as: Black S, et al., Two Year Outcome After Chronic Iliac Vein Occlusion Recanalisation Using the Vici Venous StentÒ, European Journal of Vascular and Endovascular Surgery (2018), https://doi.org/10.1016/j.ejvs.2018.07.014

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a few years ago, braided stainless steel stents and repurposed arterial stents were used almost exclusively. Long-term stent patency in post-thrombotic limbs is notably inferior to patency rates observed in limbs with nonthrombotic venous obstruction, which are generally excellent.1 In particular, post-thrombotic limbs requiring recanalisation of a chronic venous occlusion have the lowest long-term patency rates, probably owing to frequent concomitant obstructive disease in the profunda and femoropopliteal veins, resulting in decreased inflow to the stent system.1 Stent options for these challenging cases have expanded with the recent availability of dedicated venous stents in Europe, including the sinus-Venous and sinus-Obliquus stents (OptiMed, Ettlingen, Germany), ZilverÒ VenaÔ Venous Self Expanding Stent (Cook Medical, Bloomington, IN, USA), VenovoÔ Venous Stent System (Bard, Tempe, AZ, USA), and Vici Venous StentÒ (VENITI, Fremont, CA, USA). One year outcomes of a multicentre study using the Vici Venous Stent in patients with symptomatic iliofemoral obstruction are now available.2 Reported here are outcomes from a single centre experience with the Vici venous stentÒ in patients with the most severe morphological lesion, symptomatic post-thrombotic femoro-ilio-caval venous occlusion. To the authors’ knowledge, this is the first report of 24 month outcomes with a dedicated venous stent.

MATERIAL AND METHODS Device and study design The Vici Venous Stent is a dedicated venous self expanding nitinol stent with a closed cell design, uniform radial strength along its entire length, and high crush resistance. Although more rigid than open cell designs, it appears to have sufficient flexibility for physiological angles. It is currently under assessment in a US Food and Drug Administration Investigational Device Exemption trial. Patients with postthrombotic iliofemoral venous occlusion treated by placement of the Vici Venous Stent from March 2014 to October 2016 were included in this single centre, retrospective review of a prospectively maintained database. All patients had venographically documented iliac vein occlusions, with involvement of the inferior vena cava (IVC) or common femoral vein (CFV). Patients with obstruction only below the profunda and femoral vein confluence were not intervened upon. All patients included in this review had chronic postthrombotic disease with the sentinel episode of iliofemoral deep vein thrombosis (DVT) > 1 year prior to stent placement, and had failed conservative therapy (compression stockings or bandaging). Only patients with a Villalta score 5 points were included. Patients who required stenting following thrombolysis of an acute iliofemoral DVT or patients with non-thrombotic or post-thrombotic non-occlusive obstruction were excluded from the analysis. Thus, patients with the most severe morphological postthrombotic lesions were selected.

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Clinical assessments The Villalta score was used to characterise the severity of post-thrombotic syndrome (PTS) prior to stenting and at follow up assessments, in keeping with current recommendations.3 Villalta score thresholds, as originally described, were used for this analysis, with a score 5 indicating significant PTS.4e6 Scores ranging from 5 - 9 indicated mild PTS, scores of 10e14 indicated moderate PTS, and scores 15 indicated severe PTS. In order to quantify change in PTS across the whole group and allow for adequate analysis of continuous variables, patients with venous ulceration, who were considered to have severe PTS, were given a maximum score of 33. Clinically significant improvement was considered when at least a 30% reduction in pre-stenting score occurred.7 Follow up visit windows were retrospectively defined and per standard of care follow up schedules. Imaging and definitions Prior to treatment, all patients were assessed with duplex ultrasound (DUS) and cross sectional imaging. Magnetic resonance venography (MRV), computed tomography venography, or ascending venography were used for pretreatment assessment of lesion characteristics. MRV is presently exclusively used at the authors’ institution, with ascending venography employed if non-invasive imaging is equivocal. Intravascular ultrasound (IVUS) and venography were used during the intervention. In this analysis, IVUS images acquired pre- and post-stenting were used by the authors to determine the extent of vessel involvement, as venography can be insufficient.8 Patency during follow up was assessed with DUS. Stents were considered to have primary patency if it had uninterrupted patency (180 days) SI 6 (21) 1 (7) .40 No. limbs with repeat intervention 4 (8) 5 (14) .29 Stent fracture 3 (5) 0 (0) .29 Stent compression 3 (5) 2 (5) >.99 Note. Data are n (%) or median (range). SI ¼ secondary intervention. a One bilaterally treated patient had one limb (right) stented across the inguinal ligament and one limb (left) with stenting cephalad to the inguinal ligament. Therefore, this patient was excised from patient level comparisons (age, sex, bilateral stenting). b Twenty-nine limbs in 27 patients and 14 limbs in 13 patients received re-intervention in the infrainguinal and suprainguinal subsets, respectively.

lowered long-term patency rates (66e89%) in patients with recanalisations of post-thrombotic occlusions.1 One limitation acknowledged in this review was that only two of the reviewed studies used IVUS. In the present authors’ experience, IVUS was a critical adjunct to successfully delineating the extent of post-thrombotic disease and guiding accurate stent placement. This is critical for long-term treatment success in this patient population by ensuring stent coverage of the entire lesion and adequate in- and outflow of the placed stent. In a comparison of secondary patency in limbs with postthrombotic occlusion versus non-occlusive obstruction, Neglen et al. found significantly lower patency rates in those with occlusions at 32 months, regardless of whether or not the stent crossed the inguinal ligament (cumulative

secondary patency rates in post-thrombotic occlusive and non-occlusive limbs of 77% and 96%, respectively).17 Postthrombotic aetiology and stenting of occluded vessels were found by authors to be far more significant factors for loss of stent patency than stent extension beneath the inguinal ligament into the CFV. In a subsequent report on patients with post-thrombotic occlusions specifically, Raju and Neglen found that while secondary patency rates in this population were low at four years (66%), the percentage with marked relief from pain at three years was high (79%).15 The cumulative secondary patency rate in the present series was substantial, and higher than that commonly reported for patients with iliofemoral stenting of postthrombotic occlusions. Primary patency was however,

Figure 2. Secondary patency rates in limbs with stents extending beneath the inguinal ligament into the common femoral vein (n ¼ 63) and limbs with stenting terminating above the inguinal ligament (n ¼ 38; SEM < 10%). Patient number at the various follow up intervals is shown at the bottom of the graph. Please cite this article in press as: Black S, et al., Two Year Outcome After Chronic Iliac Vein Occlusion Recanalisation Using the Vici Venous StentÒ, European Journal of Vascular and Endovascular Surgery (2018), https://doi.org/10.1016/j.ejvs.2018.07.014

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Table 5. Subset analyses of clinical improvement in limbs by extent of stenting. Infrainguinal stenting (n ¼ 63) 14 (6e33)a

Suprainguinal stenting (n ¼ 38) 15 (5e33)b

p

Baseline .34 Villalta score Severe PTS 26 (43) 20 (54) .40 Moderate 25 (42) 14 (38) .68 PTS Mild PTS 9 (15) 3 (8) .53 9 (1e33)c .16 Six month 6 (0e33)a Villalta score Severe PTS 15 (25) 6 (18) .45 Moderate 7 (12) 10 (29) .05 PTS Mild PTS 14 (23) 11 (32) .33 No PTS 24 (40) 7 (21) .07 9 (3e33)c .06 12 month 7 (1e33)d Villalta score Severe PTS 6 (12) 6 (16) .53 Moderate 7 (14) 7 (18) .55 PTS Mild PTS 22 (43) 12 (3) .51 No PTS 16 (31) 9 (24) .80 7.5 (2e33)f .59 24 month 8 (1e33)e Villalta score Severe PTS 5 (12) 2 (17) .65 Moderate 5 (12) 1 (8) >.99 PTS Mild PTS 17 (41) 5 (42) >.99 No PTS 14 (34) 4 (33) >.99 Note. Data are n (%) or median (range). PTS ¼ post-thrombotic syndrome. a n ¼ 60. b n ¼ 37. c n ¼ 34. d n ¼ 51. e n ¼ 41. f n ¼ 12.

notably lower. This was partly owing to the authors’ evolving approach on the optimal threshold for reintervention. Early in the series, interventions were performed on any patient with >50% diameter reduction within the stents, regardless of symptoms, with the decision to intervene dependent entirely on imaging. Later in the series, that approach evolved to become more tolerant of in-stent stenosis and to intervene only when the patient was symptomatic. This partly explains the high rate of reintervention early in the present series. In the current study there was a non-significantly higher rate of re-intervention in patients with stents extending across the inguinal ligament. It is the authors’ practice to cover the length of venous obstruction, even if it requires stenting beneath the inguinal ligament and into the CFV. Central placement of the stent 5e10 mm beyond the obstructive lesion often led to protrusion over the contralateral vein. However, this was not “gated off”, as can occur with the Wallstent, and there were no episodes of contralateral DVT in this series of patients.The most peripheral stent

placement was to the level of the femoral and profunda vein confluence. An adequate landing zone in the CFV was found with IVUS in many cases, despite the extensive disease, therefore mitigating the need for endophlebectomy and fistula (which has been associated with significant morbidity).13 Although the cumulative rate of re-intervention was numerically greater in patients with infrainguinal stenting (46%e 37%) and the secondary patency rate was lower (79% vs. 90%), there was no statistically significant difference. In 2008, Neglen et al. reported similar outcomes in the 177 limbs stented across the inguinal ligament: stenting across the inguinal ligament was not a significant factor affecting longterm patency.17 In a recent retrospective series of chronically occluded post-thrombotic patients, Rollo et al. also found that patency in infrainguinal versus suprainguinal stent extension was statistically similar at 12 months.18 Contrary to the present authors’ experience, Rollo et al. observed that clinical outcomes were worsened in patients with infrainguinal stenting, but not to a statistically significant degree. In the present series, no clinical difference was found between these groups. Ultimately, the number of patients in each subset in which symptoms resided such that they were assessed to have either mild PTS or non-existent PTS at 2 years was virtually identical. The discrepancy here may be due, in part, to the inappropriate use of CEAP to measure outcome by Rollo et al.18 The current authors’ utilised Villalta scores to assess clinical severity and improvement as it has been established as a better metric to quantify PTS among the available clinical assessment tools.6,19 However, Villalta use was altered with respect to ulcer scoring to utilise a maximum score of 33 in the presence of an ulcer as opposed to a score of 15 for an ulcer as this would have precluded analysis of the remaining components of the Villalta scale. This issue underlines the need for further development of robust scoring measures that allow for standardised and measurable reporting of outcomes. Stent integrity is the primary concern with stenting across the inguinal ligament. All three stent fractures that occurred in the present series were beneath or peripheral to the inguinal ligament. The five events of stent compression were also observed to occur at the inguinal ligament. It was found that, in the event of stent compression, placement of a braided stent resolved stent compression and achieved better luminal patency, as assessed by IVUSdalthough owing to the low number of events, firm conclusions could not be drawn. With a rigorous surveillance program, it was found that stent integrity events can be identified and readily resolved. Despite the potential risks, it is essential to stent across the inguinal ligament if disease extends into the CFV. If the stent does not extend into a healthy vein, it is unlikely that adequate inflow will be established, and stent patency will suffer. In the present series, two significant complications were encountereddone relating to bleeding and the other stent malposition. Further work is needed to clarify the optimal type and duration of antithrombotic agents that are required following venous stenting, while multiple


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venographic projections should be taken when crossing occluded lesions to prevent inadvertently entering a large collateral. Permanent stent occlusion also occurred in 13 patients. It was observed that factors that impacted on failure in the series included non-compliance with anticoagulation therapy, coagulation disorders, failure to attend follow up surveillance scans, and inadequate inflow established to the stent. To assess what is an adequate inflow prior to stenting is currently difficult. There remains no “gold standard” metric by which to measure inflow. There are also limited means to improve inflow, if it is considered to be poor. Currently, adjunctive endophlebectomy with arteriovenous fistula creation is the only method to improve inflow at the orifices of the femoral and profunda veins, as opposed to stenting beyond the profunda-femoral confluence. Insufficient inflow was undoubtedly a factor in several stent failures, and improved methods to assess and resolve insufficient inflow should be a goal for practitioners in this area and requires further evaluation. Currently, inflow assessment is based on detection of patent vessels (either the femoral vein or profunda femoris); however, there is no standard definition or accepted classification to grade inflow. A formal evaluation tool for inflow would greatly enhance the treatment pathway. The anatomy, haemodynamics, and disease processes that affect the arterial and venous system are distinct.20 Pathophysiological scarring that occurs in post-thrombotic disease creates an external force that requires a stent with sufficient compression resistance in order to maintain a lumen. Wallstents frequently used in arterial disease have had success in treating post-thrombotic patients but have limited flexibility and challenges with positioning.21 This has led to the development of dedicated venous stents. The advent of these nitinol venous stents has radically altered treatment options for interventionalists in the last five years, with the introduction of the Vici Venous Stent, Cook Zilver Vena, Optimed sinus-Venous, Optimed sinusObliquus, and Bard Venovo Venous stents. Short-term data on single centre European experiences have been presented with the open cell design Zilver Vena and hybrid sinus-Venous stents,22,23 and one year outcomes from the feasibility phase of the VIRTUS trial of the closed cell Vici Venous Stent have now been published.2 The present study is the first report of outcomes with a dedicated venous stent at 24 months, and the first report focusing specifically on the challenging patient population presenting with postthrombotic outflow occlusion. It is hoped that this study could be added to the accumulating body of evidence supporting this technology and help update clinical guidelines in the management of patients with deep venous pathology.3 Until there are comparative data on the performance of the closed and open cell stent designs, it will be difficult to assess the relative merits and pitfalls of these designs for treatment of non-thrombotic and postthrombotic aetiologies. It will be of particular interest to assess their respective performances when crossing the area of the inguinal ligament. Also of consideration is the

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relative importance of lumen shape (i.e., the transition to a rounder lumen post stenting enabled by the closed cell design and greater radial strength). This is a marked change from the naturally elliptical shape of veins. To what extent transformation of the venous lumen to a more cylindrical configuration improves volume flow through the stent system resulting in better clinical relief and more durable stent patency is the subject of future analyses. The results from this series are encouraging for the performance of a stent with closed cell design in chronic post-thrombotic occlusions. Limitations The non-randomised retrospective nature of this analysis and the lack of a comparator arm are key limitations. In addition, the lack of any standardised definitions to describe patterns of chronic venous disease (e.g., TASC for arterial occlusive disease) and the limited adequacy of the Villalta scale make comparison between this and other published series difficult. Comparative data on treatment solutions in this challenging patient population would be highly valuable to clinicians. CONCLUSIONS In an analysis of 101 limbs (88 patients) with postthrombotic iliofemoral venous occlusions, it was found that treatment with a closed cell self expanding nitinol stent (Vici Venous Stent) led to clinical improvement in the majority of patients over 24 months. Cumulative secondary patency rates were high, and no significant differences were observed in stent patency or clinical outcomes in those patients with stents extending below the inguinal ligament. Further comparative studies with different stent types (open or closed cell) are needed. ACKNOWLEDGEMENTS The authors would like to acknowledge the significant contribution of members of the Departments of Vascular Surgery, Interventional Radiology, and Ultrasonic Angiology, and the nurses on the wards and in outpatients who help manage these patients at Guy’s and St Thomas’ Hospital. CONFLICTS OF INTEREST S.B. has consultancy contracts with Bard, Volcano Philips, Veniti, Cook, BSCI, and Medtronic. K.B. has received an honorarium from Veniti. P.S. has consultancy contracts with Bard, Volcano Philips, and Veniti. A.C. has consultancy work and has received honoraria from Astellas, Bayer, Boehringer Ingelheim, BMS, Daiichi Sankyo, GSK, J&J, Mitsubishi Pharma, Pfizer, Portola, Sanofi, and Schering Plough. A.C. has also received research support from Merck, as well as honoraria and consultancy for Takeda. A.T.C. has also undertaken scientific advisory work and speaker bureau work for Bayer, BMS, Daiichi Sankyo, J&J, Pfizer, and Sanofi. A.C. has undertaken scientific advisory board work for Portola and speaker bureau work for Boehringer Ingelheim.


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FUNDING The authors wish to thank VENITI, Inc. for its financial support to Dana Bentley (Syntactx, New York, NY, USA) for statistical analysis and editorial support of this publication.

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