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What predicts outcome after recanalization of chronic venous obstruction: hemodynamic factors, stent geometry, patient selection, anticoagulation or other factors? H Jalaie, CWKP Arnoldussen, ME Barbati, RLM Kurstjens, R de Graaf, J Grommes, A Greiner, MA de Wolf and CHA Wittens Phlebology 2014 29: 97 DOI: 10.1177/0268355514529510 The online version of this article can be found at: http://phl.sagepub.com/content/29/1_suppl/97
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Review Article
What predicts outcome after recanalization of chronic venous obstruction: hemodynamic factors, stent geometry, patient selection, anticoagulation or other factors?
Phlebology 2014, Vol. 29(1S) 97–103 ! The Author(s) 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav DOI: 10.1177/0268355514529510 phl.sagepub.com
H Jalaie1, CWKP Arnoldussen2,3, ME Barbati1, RLM Kurstjens4, R de Graaf2, J Grommes1, A Greiner1, MA de Wolf4 and CHA Wittens1,4
Abstract In this review we evaluated the effect of different suggested factors associate with the outcome after recanalization of chronic venous obstruction (CVO). Hemodynamic factors: Based upon literature no clear suggestions can be made to identify the risk of stent occlusion in association with the hemodynamic effects. However it is evident that ensuring optimal in- and outflow of the stented tract is key in maintaining the patency. Patient selection: Noninvasive imaging modalities are used to divide patients in three subgroups based on the place and extension of post-thrombotic changes. Moreover it should be noted that AV fistula in selected patients can reduce the risk of thrombosis or re-occlusion. Geometry: Excessive oversizing of the stent and stent compression from outside are considered to be associated with stent occlusion. Additionally, overlapping rigid stents, unnatural angel between stents and in-stent kinking are other geometrical factors related to worse outcome after venous recanalization. Anticoagulation: Adequate peri-and postoperative anticoagulation has a crutial role in stent patency. There is no data regarding the duration of anticoagulation therapy and recommendations vary between 6 weeks to 6 months. Result: impaired inflow or outflow, presence of a hypercoagulability, total number of treated segments and use of stents designed for implantation in arterial system are associated with decreased stent patency.
Keywords Venous recanalization, endophlebectomy, post-thrombotic syndrome, chronic venous obstruction, outcome after venous recanalization
Introduction Post-thrombotic syndrome (PTS) can be seen as the advanced manifestation of chronic venous insufficiency after a thrombotic event. Up to 80% of patients with deep vein thrombosis develop this complication within 2 years despite optimal anticoagulant therapy.1–6 Chronic venous outflow obstruction, as a result of deep vein thrombosis (DVT) with or without nonthrombotic iliocaval lesions (NIL) and venous reflux due to incompetent venous valves are two essential pathological processes that cause venous hypertension and leads to PTS.7–9 The clinical characteristics of PTS vary from leg pain, occasional swelling, eczema, and venous ectasia to extremely severe forms with disabling
pain (including incapacitating venous claudication), intractable edema and non-healing venous ulcers.4,10,11 1 European Vascular Center Aachen-Maastricht, University Hospital of the RWTH Aachen, Germany 2 Department of Diagnostic and Interventional Radiology, Maastricht University Medical Center, The Netherlands 3 Department of Radiology, Viecuri Medical Centre, Venlo, The Netherlands 4 European Vascular Center Aachen-Maastricht, Maastricht University Medical Centre, The Netherlands
Corresponding author: Houman Jalaie European Vascular Center Aachen-Maastricht, University Hospital of the RWTH Aachen, Pauwelsstr. 30, 52074 Aachen, Germany. Email: [email protected]
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Appropriate treatment of PTS is a time consuming and challenging therapeutic process that requires a multidimensional approach based on patient’s aspects, characteristics of the initial thrombosis as well as symptoms themselves. Treatment and prevention strategies in PTS are basically the same as those in DVT and consist of conservative therapy, minimally invasive (endovascular) and open surgical procedures. The conservative therapy including elastic stockings, anticoagulation and mobilization do not seem to be enough to treat or prevent PTS, especially in cases of DVT with complete outflow impairment in common femoral, iliac or caval vein.12–16 Open surgical reconstruction and endovascular recanalization alone or combined with endophlebectomy as a hybrid procedure have promising effects by improving venous outflow and thereby decreasing venous hypertension.12,13,15,17–19 Endovascular recanalization of chronic venous obstruction (CVO) can be performed with low morbidity, no mortality and high patency rates. With the introduction of new imaging modalities, improved recanalization techniques and newly developed dedicated venous stents with high flexibility and high radial force, this procedure is becoming the method of choice to treat CVO.13–15 In this manuscript we address potential factors predicting outcome after endovascular or hybrid recanalization of CVO.
Hemodynamic factors (flow, pressure) Little literature is available on the hemodynamic effect of stenting in post-thrombotic disease or stenting in iliac vein compression syndrome. No studies have specifically looked at potential predictors for stent occlusion or other stent related problems. Neglen et al. did look at ambulatory pressure drop (difference in venous pressure at the dorsal foot vein after ten tiptoe movements, expressed as a percentage), hand-foot pressure differential, and hyperemia induced pressure rise (pressure rise of the dorsal foot vein after ischemia induced reactive hyperemia) pre-operatively and tried to correlate these factors to outcome of stenting. The same was done for intra-operative pressure gradient, degree of stenosis and collateralization. However, none of the aforementioned factors proved to be a predictor for outcome.20 Additionally, outcome was measured with the use of a pain scale and degree of swelling; stent occlusion was not an outcome parameter. Therefore no conclusions can be drawn concerning potential predictors for stent occlusion. Another article by Neglen at al. describes results of stenting in a larger cohort of patients. The same tests were performed, though the focus was not on the differences in parameter between different outcomes.
Furthermore, patients who developed an occlusion of the stented tract were actually excluded from hemodynamic analysis.13 Because these patients were excluded from analysis, no speculations with reference to risk of stent occlusion can be made. Hurst et al. investigated the effect of recanalization in eighteen patients with May-Thurner syndrome (MTS). In two patients the stent occluded, one of which had a pre-procedure pressure gradient of 14 mmHg that dropped to 1 mmHg.21 Although this does not give any information on a possible hemodynamic cause for re-occlusion, it indicates that a decrease of pressure after treatment does not guarantee patency. Summarizing, based upon literature, no clear suggestions, identifying the risk of stent occlusion with reference to hemodynamic effects, can be made. However, we believe that improved hemodynamic parameters are vital in ensuring stent patency. We cannot speculate about the direct effect of a specific change in intravenous pressure or flow, but the need for these parameters to improve seems evident. Ensuring optimal in- and outflow of the stented tract is key in maintaining patency. Stents with an impaired outflow have lower in-stent flow and increased pressure that will supposedly lead to a higher coagulable state. Impaired inflow will most likely cause a lower flow and pressure within the stented tract, leading to a situation more prone for thrombosis. Therefore it is important to establish good inflow of the stented tract, possibly expanding treatment with an endophlebectomy and/or the creation of an arteriovenous fistula.
Patient selection As has been described above, in- and outflow after recanalization and stenting are crucial for stent patency. In our practice we routinely evaluate patients with PTS with duplex ultrasound (DUS) and magnetic resonance venography (MRV) prior to any intervention. These non-invasive imaging modalities are used to assess the severity of disease, which dictates the planned operation as either an endovascular only or hybrid procedure, patient positioning, access sites and materials. It is vital to treat a chronic deep vein obstruction by stenting from healthy to healthy vein. Therefore, we identify 3 subgroups of patients with a deep vein obstruction. The first group is those patients with a deep vein obstruction based on an iliac compression without post-thrombotic changes. In general these patients only require stenting of the common iliac vein and/or external iliac vein. These patients show on imaging an iliac compression, venous collaterals and no post-thrombotic changes, in particular no
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Figure 1. MRV showing post-thrombotic changes (trabeculation) in CFV (axial plane).
trabeculations/fibrotic remnants in the deep veins. We consider an iliac compression significant if it is either limited or non-reversible during dynamic evaluation with DUS and/or if we identify clear collateral pathways in conjunction with a static compression on MRV. The second group consists of those patients with a deep vein obstruction based on a post-thrombotic occlusion of the inferior vena cava, the common iliac vein and/or the external iliac vein. Crucial in the preprocedural planning of these patients is the identification of the extent of the post-thrombotic changes. In order to ensure adequate inflow, the extent of postthrombotic changes in the common femoral vein and in particular the confluence of the femoral and deep femoral vein is evaluated. Post-thrombotic changes can be easily identified with MRV, even if it is very subtle or deep into the femoral veins (Figure 1, Figure 2). Computed Tomography Venography (CTV) has been suggested as an alternative imaging modality for MRV. However, in our experience identification of post-thrombotic changes with CTV is limited to identification of obstructed ilio-caval veins. Collateral pathways are less clearly demarcated as well as post-thrombotic trabeculations, which in our opinion limit the pre-procedural value of CTV. If the post-thrombotic changes in common femoral vein (CFV) do not extend below the confluence of the deep femoral vein, an endovascular-only approach is feasible. To stent from a healthy segment proximal to a healthy segment distal, stenting below the inguinal ligament is required in these patients. Stenting below the inguinal ligament is not an issue in the deep venous system as long as the distal landing zone is above the femoral confluence and free of post-thrombotic changes. If however the CFV and femoral vein confluence are involved, an isolated endovascular procedure does not suffice. In this third group of patients, an endophlebectomy of the CFV and femoral vein confluence in combination with the creation of an AV-fistula is required to ensure adequate flow into the stented
Figure 2. MRV showing post-thrombotic changes (trabeculation) in CFV (coronal plane).
iliac tract. The endophlebectomy allows adequate flow from the femoral veins into the stented segment (Figure 3). The AV-fistula is a temporary measure to support the remodeling process in the endophlebectomy space and allow for adequate endothelial covering of the stents to prevent post-procedural thrombosis/re-occlusion. There is currently no published data on the appropriate time for closing the AV-fistula but the current centers of expertise that perform this procedure seem to agree that it is between 6 weeks and 3 months which is equal to our experience.
Stent geometry Two aspects of stent geometry are of importance in relation to outcome; geometry of one stent and the interplay between multiple stents. In case of NIL, most often a left iliac vein compression syndrome, also known as a May-Thurner syndrome (MTS), generally no geometric problems arise. Only one stent is generally needed in these cases, as only the crossing of the common iliac artery needs to be stented. Possible stent related problems in these cases might be protrusion of the stent into the caval vein, and thereby potentially interfering the outflow tract of the right common iliac vein. This is common in one of the techniques described for MTS with the use of Wallstents, as the Wallstent needs to be anchored into the contralateral caval wall to secure the stent from tapering.13 Moreover, problems can arise when the stent for the common iliac vein is improperly sized. In oversizing the stent cannot fully deploy its true diameter; to accommodate this the stent may implode on itself resulting in a ‘‘web’’ of struts protruding into the vein lumen (Figure 4). In both types of described geometry, metal stent material is present in the venous lumen, as this material is inherently thrombogenous, impairs flow and
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Figure 3. Removal of post-thrombotic changes (endophlebectomy) in CFV to improve the inflow.
Figure 4. Schematic drawing of a stent properly sized on the left and stent invaginated on itself on the right.
causes turbulences, with possibly thrombotic complications as a result. Due to bad alignment to the veinwall it also doesn’t get well incorporated in the veinwall, as one would normally expect to happen, and thereby the risk of stent occlusion is theoretically possible in case of undersizing, the risk of stent migration is significant. Furthermore, in both cases of external compression to the vein and post-thrombotic aberrations in the venous lumen, residual compression after stent placement can be observed. Generally the degree of stenosis is less severe than before stent placement but the flow can still be impaired; however the fact that mild to moderate stent compression causes stent occlusion is not yet established. Treatment in these cases can be either conservative, possibly increasing the duration of postoperative anticoagulation therapy, or interventional by balloon dilation and possibly stent-in-stent placement. Secondly geometrical problems can arise when multiple stents are used and alignment is not ideal. This can generally be avoided by not overlapping stents, however it should be considered that skip-lesions would be present, which are known to lead to stenosis in arterial stenting. The importance of skip-lesions in venous stenting has not yet been established. However in cases of post-thrombotic syndrome, which most cases with multiple stent deployment are, it is generally discouraged to leave any post-thrombotic lesion in the
Figure 5. Three rigid stents in the iliac tract showing pivoting at the stent connections and un-physiological angulation, giving a bamboo-like appearance.
iliocaval and common femoral vein tract untreated. In our experience the most significant stent related problems arise when multiple rigid (low-flexibility) stents are used in venous segments within a natural curved trajectory. Because these types of stents try to force a nonphysiological geometry in the veins a bamboo-like appearance can be seen on X-ray control images (Figure 5). Two important forms of stenosis can be attributed to this type of stent alignment. Firstly, angulation of the vein at the level of connection between two stents, can lead to an unnatural angle in treated segments, sometimes approaching 45 degrees (Figure 5). At these sites of intersection severe stenosis may be present necessitating interventions to maintain patency or restore patency in case of re-thrombosis. More frequently we have observed in-stent kinking, with or without stent fracture, when using rigid stents designed for the arterial system (Figure 6). Stent deformation in such cases can lead to stent struts being present inside the venous lumen, with possible complications as described above. Moreover, non-thrombotic stenosis is found in such cases of kinking leading to re-occlusion or necessity for re-intervention. It has to be realized that the connection between the external and common iliac angulates most significant with angles up to 120 degrees in a sitting position. The connection between
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Figure 6. Stented iliac tract. One stent showing clear kinking.
the external iliac and common femoral vein can also cause angulation, but is normally less with angles up to 90 degrees. Most of the above described geometrical problems arise when stents with suboptimal design for the venous system are used. In our experience geometric problems are seen significantly less frequent when using dedicated venous stents with higher flexibility and higher radial force. The Cook Zilver Vena has for instance a better flexibility than arterial stents and the Optimed Sinus Venous combines a higher flexibility with a high radial force due to a segmental design. However comparative literature in this area on both stent geometry and clinical results after using dedicated venous stents is still lacking at this moment. Nevertheless, in general the venous geometry should dictate the shape of the stent and not vice versa.
Anticoagulation Thrombotic events are a common complication after endovascular or hybrid venous recanalization. There are some possible mechanisms causing early thrombosis after venous recanalization. Thrombophilia, venous manipulation, endophlebectomy and hematomas, causing compression of the recanalized segment and postoperative immobilization, causing a low flow state, are well-known thrombogenic factors. The role of thrombophilia in PTS is controversial but most studies suggest a notable relation between thrombophilia and PTS with prevalence rates of up to 50% of patients in these studies.13,14,22 Negle´n et al. did look at the risk factors associated with in-stent stenosis and found that presence of thrombotic disease and
positive thrombophilia are two factors affecting stent outcome .20,23 The fact that this kind of hypercoagulability is not a transient state can justify the peri- and postoperative anticoagulation therapy as a preventive strategy in these patients.15 Continuous adequate anticoagulation is one of the main issues after recanalization and considered to be vital for stent patency.13,22 Primary and secondary stent patency rates appear to be primarily related to thrombotic events and the severity of thrombotic disease12,13 Most of the studies regarding recanalization of CVO showed that the stent-related outcome was influenced by presence and severity of thrombotic disease and positive thrombophilia test results.13,23 Therefore adequate peri-and postoperative anticoagulation has an crucial role in stent patency by reducing the rate of postoperative thrombotic events.15 There is no data regarding the duration of anticoagulation therapy and recommendations vary between 6 weeks to six months postoperatively.24 Raju and Neglen recommend long-term oral anticoagulation in most patients with long (3) segment occlusions, underlying thrombophilia, suprarenal occlusions and previous long-term anticoagulation. Additionally long-term anticoagulation is recommended if the completion venography suggests impaired in and or outflow.23,24 In our center, we perform endovascular or hybrid venous recanalization with an endophlebectomy of the common femoral vein (CFV) under therapeutic anticoagulation. During the intervention we use 5000 IU of unfractionated heparin as initial anticoagulation. During the operation the anticoagulation can be measured by activating clotting time (ACT) and if needed additional heparin is given. Postoperatively, all patients will start or continue therapeutic anticoagulation therapy with oral anticoagulants. We continue anticoagulation for six months after the intervention if there is no other risk factor except the presence of a venous stent. In summary, it can be stated that in venous recanalization the anticoagulant management is not evidence based. Individual patients characteristics and risk factors will have to determine the optimal anticoagulation.26,26
Literature review In a retrospective observational study in 63 patients with chronic deep vein obstruction De Wolf et al. have shown that poor stent inflow is an important risk factor for re-occlusion. In their study patients with MTS have a lower risk for re-thrombosis compare with the subpopulation with obstruction secondary to DVT. As they tested only 33% of patients for
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thrombophilia, they couldn’t show a clear effect of thrombophilia disorders on stent patency rate.14. In contrary, Garg et al. revealed in a retrospective study in 60 patients with chronic vein obstruction that MTS, as a cause for initial thrombotic occlusion, was associated with worse patency rates. Furthermore, in their study use of arteriovenous fistula was related to lower patency rate.19 In 2007 Neglen et al. have published a study on 982 patients with chronic nonmalignant obstructive lesions who were stented under intravascular ultrasound (IVUS) guidance. Although thrombophilia was more frequent in limbs with thrombotic events it was not statistically related with a higher stent occlusion rate. Respectively, the operation side and gender did not influence stent outcome, but younger age appeared to do so. Also the number of stents, length of stented area and extension of the stent into the common femoral vein were associated with higher risk of stent occlusion and development of in-stent restenosis.13 In another prospective study in 52 patients with PTS, presence of thrombophilia and in-flow problem has been suggested to be associated with early stent occlusion. Although in this study twenty-one patients (40.1%) had documented hypercoagulable states it was not statistically associated with a higher rate of stent occlusion.24 Ye et al. reported the primary and assisted-primary stent patency rate of 98.7% and 100% respectively, in 205 stented patients with nonthrombotic iliac vein compression lesions after 4 years of follow up. It should be noted that they excluded all patients with PTS and acute or chronic deep vein thrombosis from this study. The high patency rate of stenting in these highly selected patients can be suggestive for the role of hypercoagulability in stent outcome in the PTS group.29 Hartung et al. also published their long-term results in 89 patients who underwent stenting and followed up for a median time of 38 months. Primary, assisted-primary and secondary stent patency rate were 83%, 89% and 93% respectively. In univariate analysis common femoral vein lesion was related to a lower primary patency rate but this relation faded after adding other variables to analysis. Small sample size could be the reason of low predictive power in this multivariate analysis.22
Conclusion and recommendation Venous stenting differs from arterial interventions and different factors seem to be important in both early thrombosis and late re-stenosis. Regarding the literature and our experience inadequate anticoagulation, impaired inflow or outflow, presence of a hypercoagulability, total number of
treated segments and use of stents with suboptimal design for the venous system are associated with decreased stent patency, because they all potentially increase thrombotic occlusions. Therefore adequate anticoagulation, measures to improve inflow (mobilization, compression stockings, pneumatic compression) and outflow, using dedicated venous stents and good follow-up for early detecting stent-failure are essential for a better patency rate and outcome.
Conflict of interest All the authors have no conflict of interest and nothing to disclose.
Funding This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors
References 1. Wille-Jorgensen P, Jorgensen LN and Crawford M. Asymptomatic postoperative deep vein thrombosis and the development of postthrombotic syndrome. A systematic review and meta-analysis. Thrombosis and haemostasis 2005; 93: 236–41. 2. Ziegler S, Schillinger M, Maca TH and Minar E. Postthrombotic syndrome after primary event of deep venous thrombosis 10 to 20 years ago. Thrombosis research 2001; 101: 23–33. 3. Bernardi E and Prandoni P. The post-thrombotic syndrome. Current opinion in pulmonary medicine 2000; 6: 335–42. 4. Kahn SR and Ginsberg JS. The post-thrombotic syndrome: current knowledge, controversies, and directions for future research. Blood reviews 2002; 16: 155–65. 5. Saarinen J, Kallio T, Lehto M, Hiltunen S and Sisto T. The occurrence of the post-thrombotic changes after an acute deep venous thrombosis. A prospective two-year follow-up study. The Journal of cardiovascular surgery 2000; 41: 441–6. 6. Kahn SR. The post-thrombotic syndrome: progress and pitfalls. Br J Haematol 2006; 134: 357–65. 7. Belcaro G, Grigg M, Rulo A and Nicolaides A. Blood flow in the perimalleolar skin in relation to posture in patients with venous hypertension. Annals of vascular surgery 1989; 3: 5–7. 8. Hjelmstedt A. Pressure decrease in the dorsal pedal veins on walking in persons with and without thrombosis. A study of a fracture series. Acta chirurgica Scandinavica 1968; 134: 531–9. 9. Khanna AK and Singh S. Postthrombotic syndrome: surgical possibilities. Thrombosis 2012 2012; 520–604. 10. Ruckley CV. Socioeconomic impact of chronic venous insufficiency and leg ulcers. Angiology 1997; 48: 67–9.
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11. Smith JJ, Guest MG, Greenhalgh RM and Davies AH. Measuring the quality of life in patients with venous ulcers. J Vasc Surg 2000; 31: 642–9. 12. Hartung O, Otero A, Boufi M, De Caridi G, Barthelemy P, Juhan C, et al. Mid-term results of endovascular treatment for symptomatic chronic nonmalignant iliocaval venous occlusive disease. J Vasc Surg 2005; 42: 1138–44. (discussion 44). 13. Neglen P, Hollis KC, Olivier J and Raju S. Stenting of the venous outflow in chronic venous disease: long-term stent-related outcome, clinical, and hemodynamic result. J Vasc Surg 2007; 46: 979–90. 14. Friedrich de Wolf MA, Arnoldussen CW, Grommes J, Hsien SG, Nelemans PJ, de Haan MW, et al. Minimally invasive treatment of chronic iliofemoral venous occlusive disease. Journal of Vascular Surgery: Venous and Lymphatic Disorders 2013; 1: 146–53. 15. de Graaf R, Arnoldussen C and Wittens CH. Stenting for chronic venous obstructions a new era. Phlebology 2013; 28(Suppl 1): 117–22. 16. Knipp BS, Ferguson E, Williams DM, Dasika NJ, Cwikiel W, Henke PK, et al. Factors associated with outcome after interventional treatment of symptomatic iliac vein compression syndrome. J Vasc Surg 2007; 46: 743–9. 17. Alguire PC and Mathes BM. Chronic venous insufficiency and venous ulceration. Journal of general internal medicine 1997; 12: 374–83. 18. Bond RT, Cohen JM, Comerota A and Kahn SR. Surgical treatment of moderate-to-severe post-thrombotic syndrome. Ann Vasc Surg 2013; 27: 242–58. 19. Garg N, Gloviczki P, Karimi KM, Duncan AA, Bjarnason H, Kalra M, et al. Factors affecting outcome of open and hybrid reconstructions for nonmalignant obstruction of iliofemoral veins and inferior vena cava. J Vasc Surg 2010; 53: 383–93.
20. Neglen P and Raju S. Balloon dilation and stenting of chronic iliac vein obstruction: technical aspects and early clinical outcome. J Endovasc Ther 2000; 7: 79–91. 21. Hurst DR, Forauer AR, Bloom JR, Greenfield LJ, Wakefield TW and Williams DM. Diagnosis and endovascular treatment of iliocaval compression syndrome. J Vasc Surg 2001; 34: 106–13. 22. Hartung O, Loundou AD, Barthelemy P, Arnoux D, Boufi M and Alimi YS. Endovascular management of chronic disabling ilio-caval obstructive lesions: longterm results. Eur J Vasc Endovasc Surg 2009; 38: 118–24. 23. Raju S and Neglen P. Percutaneous recanalization of total occlusions of the iliac vein. J Vasc Surg 2009; 50: 360–8. 24. Sarici IS, Yanar F, Agcaoglu O, Ucar A, Poyanli A, Cakir S, et al. Our early experience with iliofemoral vein stenting in patients with post-thrombotic syndrome. Phlebology 2013; Epub ahead of print, DOI: 10.1177/ 0268355513477641. 25. Ten Cate-Hoek AJ, Prins MH, Wittens CH and ten Cate H. Postintervention duration of anticoagulation in venous surgery. Phlebology 2013; 28(Suppl 1): 105–11. 26. Meissner MH. Indications for platelet aggregation inhibitors after venous stents. Phlebology 2013; 28(Suppl 1): 91–8. 27. Neglen P and Raju S. In-stent recurrent stenosis in stents placed in the lower extremity venous outflow tract. J Vasc Surg 2004; 39: 181–7. 28. Titus JM, Moise MA, Bena J, Lyden SP and Clair DG. Iliofemoral stenting for venous occlusive disease. J Vasc Surg 2011; 53: 706–12. 29. Ye K, Lu X, Li W, Huang Y, Huang X, Lu M, et al. Long-term outcomes of stent placement for symptomatic nonthrombotic iliac vein compression lesions in chronic venous disease. J Vasc Interv Radiol 2012; 23: 497–502.
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What predicts outcome after recanalization of chronic venous obstruction: hemodynamic factors, stent geometry, patient selection, anticoagulation or other factors? H Jalaie, CWKP Arnoldussen, ME Barbati, RLM Kurstjens, R de Graaf, J Grommes, A Greiner, MA de Wolf and CHA Wittens Phlebology 2014 29: 97 DOI: 10.1177/0268355514529510 The online version of this article can be found at: http://phl.sagepub.com/content/29/1_suppl/97
Published by: http://www.sagepublications.com
Additional services and information for Phlebology can be found at: Email Alerts: http://phl.sagepub.com/cgi/alerts Subscriptions: http://phl.sagepub.com/subscriptions Reprints: http://www.sagepub.com/journalsReprints.nav Permissions: http://www.sagepub.com/journalsPermissions.nav
>> Version of Record - May 19, 2014 What is This?
Downloaded from phl.sagepub.com at OhioLink on November 10, 2014
Review Article
What predicts outcome after recanalization of chronic venous obstruction: hemodynamic factors, stent geometry, patient selection, anticoagulation or other factors?
Phlebology 2014, Vol. 29(1S) 97–103 ! The Author(s) 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav DOI: 10.1177/0268355514529510 phl.sagepub.com
H Jalaie1, CWKP Arnoldussen2,3, ME Barbati1, RLM Kurstjens4, R de Graaf2, J Grommes1, A Greiner1, MA de Wolf4 and CHA Wittens1,4
Abstract In this review we evaluated the effect of different suggested factors associate with the outcome after recanalization of chronic venous obstruction (CVO). Hemodynamic factors: Based upon literature no clear suggestions can be made to identify the risk of stent occlusion in association with the hemodynamic effects. However it is evident that ensuring optimal in- and outflow of the stented tract is key in maintaining the patency. Patient selection: Noninvasive imaging modalities are used to divide patients in three subgroups based on the place and extension of post-thrombotic changes. Moreover it should be noted that AV fistula in selected patients can reduce the risk of thrombosis or re-occlusion. Geometry: Excessive oversizing of the stent and stent compression from outside are considered to be associated with stent occlusion. Additionally, overlapping rigid stents, unnatural angel between stents and in-stent kinking are other geometrical factors related to worse outcome after venous recanalization. Anticoagulation: Adequate peri-and postoperative anticoagulation has a crutial role in stent patency. There is no data regarding the duration of anticoagulation therapy and recommendations vary between 6 weeks to 6 months. Result: impaired inflow or outflow, presence of a hypercoagulability, total number of treated segments and use of stents designed for implantation in arterial system are associated with decreased stent patency.
Keywords Venous recanalization, endophlebectomy, post-thrombotic syndrome, chronic venous obstruction, outcome after venous recanalization
Introduction Post-thrombotic syndrome (PTS) can be seen as the advanced manifestation of chronic venous insufficiency after a thrombotic event. Up to 80% of patients with deep vein thrombosis develop this complication within 2 years despite optimal anticoagulant therapy.1–6 Chronic venous outflow obstruction, as a result of deep vein thrombosis (DVT) with or without nonthrombotic iliocaval lesions (NIL) and venous reflux due to incompetent venous valves are two essential pathological processes that cause venous hypertension and leads to PTS.7–9 The clinical characteristics of PTS vary from leg pain, occasional swelling, eczema, and venous ectasia to extremely severe forms with disabling
pain (including incapacitating venous claudication), intractable edema and non-healing venous ulcers.4,10,11 1 European Vascular Center Aachen-Maastricht, University Hospital of the RWTH Aachen, Germany 2 Department of Diagnostic and Interventional Radiology, Maastricht University Medical Center, The Netherlands 3 Department of Radiology, Viecuri Medical Centre, Venlo, The Netherlands 4 European Vascular Center Aachen-Maastricht, Maastricht University Medical Centre, The Netherlands
Corresponding author: Houman Jalaie European Vascular Center Aachen-Maastricht, University Hospital of the RWTH Aachen, Pauwelsstr. 30, 52074 Aachen, Germany. Email: [email protected]
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Appropriate treatment of PTS is a time consuming and challenging therapeutic process that requires a multidimensional approach based on patient’s aspects, characteristics of the initial thrombosis as well as symptoms themselves. Treatment and prevention strategies in PTS are basically the same as those in DVT and consist of conservative therapy, minimally invasive (endovascular) and open surgical procedures. The conservative therapy including elastic stockings, anticoagulation and mobilization do not seem to be enough to treat or prevent PTS, especially in cases of DVT with complete outflow impairment in common femoral, iliac or caval vein.12–16 Open surgical reconstruction and endovascular recanalization alone or combined with endophlebectomy as a hybrid procedure have promising effects by improving venous outflow and thereby decreasing venous hypertension.12,13,15,17–19 Endovascular recanalization of chronic venous obstruction (CVO) can be performed with low morbidity, no mortality and high patency rates. With the introduction of new imaging modalities, improved recanalization techniques and newly developed dedicated venous stents with high flexibility and high radial force, this procedure is becoming the method of choice to treat CVO.13–15 In this manuscript we address potential factors predicting outcome after endovascular or hybrid recanalization of CVO.
Hemodynamic factors (flow, pressure) Little literature is available on the hemodynamic effect of stenting in post-thrombotic disease or stenting in iliac vein compression syndrome. No studies have specifically looked at potential predictors for stent occlusion or other stent related problems. Neglen et al. did look at ambulatory pressure drop (difference in venous pressure at the dorsal foot vein after ten tiptoe movements, expressed as a percentage), hand-foot pressure differential, and hyperemia induced pressure rise (pressure rise of the dorsal foot vein after ischemia induced reactive hyperemia) pre-operatively and tried to correlate these factors to outcome of stenting. The same was done for intra-operative pressure gradient, degree of stenosis and collateralization. However, none of the aforementioned factors proved to be a predictor for outcome.20 Additionally, outcome was measured with the use of a pain scale and degree of swelling; stent occlusion was not an outcome parameter. Therefore no conclusions can be drawn concerning potential predictors for stent occlusion. Another article by Neglen at al. describes results of stenting in a larger cohort of patients. The same tests were performed, though the focus was not on the differences in parameter between different outcomes.
Furthermore, patients who developed an occlusion of the stented tract were actually excluded from hemodynamic analysis.13 Because these patients were excluded from analysis, no speculations with reference to risk of stent occlusion can be made. Hurst et al. investigated the effect of recanalization in eighteen patients with May-Thurner syndrome (MTS). In two patients the stent occluded, one of which had a pre-procedure pressure gradient of 14 mmHg that dropped to 1 mmHg.21 Although this does not give any information on a possible hemodynamic cause for re-occlusion, it indicates that a decrease of pressure after treatment does not guarantee patency. Summarizing, based upon literature, no clear suggestions, identifying the risk of stent occlusion with reference to hemodynamic effects, can be made. However, we believe that improved hemodynamic parameters are vital in ensuring stent patency. We cannot speculate about the direct effect of a specific change in intravenous pressure or flow, but the need for these parameters to improve seems evident. Ensuring optimal in- and outflow of the stented tract is key in maintaining patency. Stents with an impaired outflow have lower in-stent flow and increased pressure that will supposedly lead to a higher coagulable state. Impaired inflow will most likely cause a lower flow and pressure within the stented tract, leading to a situation more prone for thrombosis. Therefore it is important to establish good inflow of the stented tract, possibly expanding treatment with an endophlebectomy and/or the creation of an arteriovenous fistula.
Patient selection As has been described above, in- and outflow after recanalization and stenting are crucial for stent patency. In our practice we routinely evaluate patients with PTS with duplex ultrasound (DUS) and magnetic resonance venography (MRV) prior to any intervention. These non-invasive imaging modalities are used to assess the severity of disease, which dictates the planned operation as either an endovascular only or hybrid procedure, patient positioning, access sites and materials. It is vital to treat a chronic deep vein obstruction by stenting from healthy to healthy vein. Therefore, we identify 3 subgroups of patients with a deep vein obstruction. The first group is those patients with a deep vein obstruction based on an iliac compression without post-thrombotic changes. In general these patients only require stenting of the common iliac vein and/or external iliac vein. These patients show on imaging an iliac compression, venous collaterals and no post-thrombotic changes, in particular no
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Figure 1. MRV showing post-thrombotic changes (trabeculation) in CFV (axial plane).
trabeculations/fibrotic remnants in the deep veins. We consider an iliac compression significant if it is either limited or non-reversible during dynamic evaluation with DUS and/or if we identify clear collateral pathways in conjunction with a static compression on MRV. The second group consists of those patients with a deep vein obstruction based on a post-thrombotic occlusion of the inferior vena cava, the common iliac vein and/or the external iliac vein. Crucial in the preprocedural planning of these patients is the identification of the extent of the post-thrombotic changes. In order to ensure adequate inflow, the extent of postthrombotic changes in the common femoral vein and in particular the confluence of the femoral and deep femoral vein is evaluated. Post-thrombotic changes can be easily identified with MRV, even if it is very subtle or deep into the femoral veins (Figure 1, Figure 2). Computed Tomography Venography (CTV) has been suggested as an alternative imaging modality for MRV. However, in our experience identification of post-thrombotic changes with CTV is limited to identification of obstructed ilio-caval veins. Collateral pathways are less clearly demarcated as well as post-thrombotic trabeculations, which in our opinion limit the pre-procedural value of CTV. If the post-thrombotic changes in common femoral vein (CFV) do not extend below the confluence of the deep femoral vein, an endovascular-only approach is feasible. To stent from a healthy segment proximal to a healthy segment distal, stenting below the inguinal ligament is required in these patients. Stenting below the inguinal ligament is not an issue in the deep venous system as long as the distal landing zone is above the femoral confluence and free of post-thrombotic changes. If however the CFV and femoral vein confluence are involved, an isolated endovascular procedure does not suffice. In this third group of patients, an endophlebectomy of the CFV and femoral vein confluence in combination with the creation of an AV-fistula is required to ensure adequate flow into the stented
Figure 2. MRV showing post-thrombotic changes (trabeculation) in CFV (coronal plane).
iliac tract. The endophlebectomy allows adequate flow from the femoral veins into the stented segment (Figure 3). The AV-fistula is a temporary measure to support the remodeling process in the endophlebectomy space and allow for adequate endothelial covering of the stents to prevent post-procedural thrombosis/re-occlusion. There is currently no published data on the appropriate time for closing the AV-fistula but the current centers of expertise that perform this procedure seem to agree that it is between 6 weeks and 3 months which is equal to our experience.
Stent geometry Two aspects of stent geometry are of importance in relation to outcome; geometry of one stent and the interplay between multiple stents. In case of NIL, most often a left iliac vein compression syndrome, also known as a May-Thurner syndrome (MTS), generally no geometric problems arise. Only one stent is generally needed in these cases, as only the crossing of the common iliac artery needs to be stented. Possible stent related problems in these cases might be protrusion of the stent into the caval vein, and thereby potentially interfering the outflow tract of the right common iliac vein. This is common in one of the techniques described for MTS with the use of Wallstents, as the Wallstent needs to be anchored into the contralateral caval wall to secure the stent from tapering.13 Moreover, problems can arise when the stent for the common iliac vein is improperly sized. In oversizing the stent cannot fully deploy its true diameter; to accommodate this the stent may implode on itself resulting in a ‘‘web’’ of struts protruding into the vein lumen (Figure 4). In both types of described geometry, metal stent material is present in the venous lumen, as this material is inherently thrombogenous, impairs flow and
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Figure 3. Removal of post-thrombotic changes (endophlebectomy) in CFV to improve the inflow.
Figure 4. Schematic drawing of a stent properly sized on the left and stent invaginated on itself on the right.
causes turbulences, with possibly thrombotic complications as a result. Due to bad alignment to the veinwall it also doesn’t get well incorporated in the veinwall, as one would normally expect to happen, and thereby the risk of stent occlusion is theoretically possible in case of undersizing, the risk of stent migration is significant. Furthermore, in both cases of external compression to the vein and post-thrombotic aberrations in the venous lumen, residual compression after stent placement can be observed. Generally the degree of stenosis is less severe than before stent placement but the flow can still be impaired; however the fact that mild to moderate stent compression causes stent occlusion is not yet established. Treatment in these cases can be either conservative, possibly increasing the duration of postoperative anticoagulation therapy, or interventional by balloon dilation and possibly stent-in-stent placement. Secondly geometrical problems can arise when multiple stents are used and alignment is not ideal. This can generally be avoided by not overlapping stents, however it should be considered that skip-lesions would be present, which are known to lead to stenosis in arterial stenting. The importance of skip-lesions in venous stenting has not yet been established. However in cases of post-thrombotic syndrome, which most cases with multiple stent deployment are, it is generally discouraged to leave any post-thrombotic lesion in the
Figure 5. Three rigid stents in the iliac tract showing pivoting at the stent connections and un-physiological angulation, giving a bamboo-like appearance.
iliocaval and common femoral vein tract untreated. In our experience the most significant stent related problems arise when multiple rigid (low-flexibility) stents are used in venous segments within a natural curved trajectory. Because these types of stents try to force a nonphysiological geometry in the veins a bamboo-like appearance can be seen on X-ray control images (Figure 5). Two important forms of stenosis can be attributed to this type of stent alignment. Firstly, angulation of the vein at the level of connection between two stents, can lead to an unnatural angle in treated segments, sometimes approaching 45 degrees (Figure 5). At these sites of intersection severe stenosis may be present necessitating interventions to maintain patency or restore patency in case of re-thrombosis. More frequently we have observed in-stent kinking, with or without stent fracture, when using rigid stents designed for the arterial system (Figure 6). Stent deformation in such cases can lead to stent struts being present inside the venous lumen, with possible complications as described above. Moreover, non-thrombotic stenosis is found in such cases of kinking leading to re-occlusion or necessity for re-intervention. It has to be realized that the connection between the external and common iliac angulates most significant with angles up to 120 degrees in a sitting position. The connection between
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Figure 6. Stented iliac tract. One stent showing clear kinking.
the external iliac and common femoral vein can also cause angulation, but is normally less with angles up to 90 degrees. Most of the above described geometrical problems arise when stents with suboptimal design for the venous system are used. In our experience geometric problems are seen significantly less frequent when using dedicated venous stents with higher flexibility and higher radial force. The Cook Zilver Vena has for instance a better flexibility than arterial stents and the Optimed Sinus Venous combines a higher flexibility with a high radial force due to a segmental design. However comparative literature in this area on both stent geometry and clinical results after using dedicated venous stents is still lacking at this moment. Nevertheless, in general the venous geometry should dictate the shape of the stent and not vice versa.
Anticoagulation Thrombotic events are a common complication after endovascular or hybrid venous recanalization. There are some possible mechanisms causing early thrombosis after venous recanalization. Thrombophilia, venous manipulation, endophlebectomy and hematomas, causing compression of the recanalized segment and postoperative immobilization, causing a low flow state, are well-known thrombogenic factors. The role of thrombophilia in PTS is controversial but most studies suggest a notable relation between thrombophilia and PTS with prevalence rates of up to 50% of patients in these studies.13,14,22 Negle´n et al. did look at the risk factors associated with in-stent stenosis and found that presence of thrombotic disease and
positive thrombophilia are two factors affecting stent outcome .20,23 The fact that this kind of hypercoagulability is not a transient state can justify the peri- and postoperative anticoagulation therapy as a preventive strategy in these patients.15 Continuous adequate anticoagulation is one of the main issues after recanalization and considered to be vital for stent patency.13,22 Primary and secondary stent patency rates appear to be primarily related to thrombotic events and the severity of thrombotic disease12,13 Most of the studies regarding recanalization of CVO showed that the stent-related outcome was influenced by presence and severity of thrombotic disease and positive thrombophilia test results.13,23 Therefore adequate peri-and postoperative anticoagulation has an crucial role in stent patency by reducing the rate of postoperative thrombotic events.15 There is no data regarding the duration of anticoagulation therapy and recommendations vary between 6 weeks to six months postoperatively.24 Raju and Neglen recommend long-term oral anticoagulation in most patients with long (3) segment occlusions, underlying thrombophilia, suprarenal occlusions and previous long-term anticoagulation. Additionally long-term anticoagulation is recommended if the completion venography suggests impaired in and or outflow.23,24 In our center, we perform endovascular or hybrid venous recanalization with an endophlebectomy of the common femoral vein (CFV) under therapeutic anticoagulation. During the intervention we use 5000 IU of unfractionated heparin as initial anticoagulation. During the operation the anticoagulation can be measured by activating clotting time (ACT) and if needed additional heparin is given. Postoperatively, all patients will start or continue therapeutic anticoagulation therapy with oral anticoagulants. We continue anticoagulation for six months after the intervention if there is no other risk factor except the presence of a venous stent. In summary, it can be stated that in venous recanalization the anticoagulant management is not evidence based. Individual patients characteristics and risk factors will have to determine the optimal anticoagulation.26,26
Literature review In a retrospective observational study in 63 patients with chronic deep vein obstruction De Wolf et al. have shown that poor stent inflow is an important risk factor for re-occlusion. In their study patients with MTS have a lower risk for re-thrombosis compare with the subpopulation with obstruction secondary to DVT. As they tested only 33% of patients for
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thrombophilia, they couldn’t show a clear effect of thrombophilia disorders on stent patency rate.14. In contrary, Garg et al. revealed in a retrospective study in 60 patients with chronic vein obstruction that MTS, as a cause for initial thrombotic occlusion, was associated with worse patency rates. Furthermore, in their study use of arteriovenous fistula was related to lower patency rate.19 In 2007 Neglen et al. have published a study on 982 patients with chronic nonmalignant obstructive lesions who were stented under intravascular ultrasound (IVUS) guidance. Although thrombophilia was more frequent in limbs with thrombotic events it was not statistically related with a higher stent occlusion rate. Respectively, the operation side and gender did not influence stent outcome, but younger age appeared to do so. Also the number of stents, length of stented area and extension of the stent into the common femoral vein were associated with higher risk of stent occlusion and development of in-stent restenosis.13 In another prospective study in 52 patients with PTS, presence of thrombophilia and in-flow problem has been suggested to be associated with early stent occlusion. Although in this study twenty-one patients (40.1%) had documented hypercoagulable states it was not statistically associated with a higher rate of stent occlusion.24 Ye et al. reported the primary and assisted-primary stent patency rate of 98.7% and 100% respectively, in 205 stented patients with nonthrombotic iliac vein compression lesions after 4 years of follow up. It should be noted that they excluded all patients with PTS and acute or chronic deep vein thrombosis from this study. The high patency rate of stenting in these highly selected patients can be suggestive for the role of hypercoagulability in stent outcome in the PTS group.29 Hartung et al. also published their long-term results in 89 patients who underwent stenting and followed up for a median time of 38 months. Primary, assisted-primary and secondary stent patency rate were 83%, 89% and 93% respectively. In univariate analysis common femoral vein lesion was related to a lower primary patency rate but this relation faded after adding other variables to analysis. Small sample size could be the reason of low predictive power in this multivariate analysis.22
Conclusion and recommendation Venous stenting differs from arterial interventions and different factors seem to be important in both early thrombosis and late re-stenosis. Regarding the literature and our experience inadequate anticoagulation, impaired inflow or outflow, presence of a hypercoagulability, total number of
treated segments and use of stents with suboptimal design for the venous system are associated with decreased stent patency, because they all potentially increase thrombotic occlusions. Therefore adequate anticoagulation, measures to improve inflow (mobilization, compression stockings, pneumatic compression) and outflow, using dedicated venous stents and good follow-up for early detecting stent-failure are essential for a better patency rate and outcome.
Conflict of interest All the authors have no conflict of interest and nothing to disclose.
Funding This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors
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