Abstract: Sizing of iliac vein stents remains controversial. We present the first Venovo venous stent (BD/Bard) that was explanted because of worsening of back and leg pain post treatment and analyze data from the first 50 consecutive Venovo venous stents from our center. Stent size was obtained with intravascular ultrasound of the ipsilateral common iliac vein. The data indicate that there is no statistical relationship between the stent size and worsening or emergence of low back and leg pain. Patient-specific factors may be contributing to this extremely rare and persistent pain beyond the 30-day follow-up.
J INVASIVE CARDIOL 2020;32(10):E250-E253.
Key words: chronic low back pain, iliac vein stent, stent size, Venovo stent, Wallstent
Sizing of iliac vein stents remains a controversial topic.1 Most recommendations on stenting the iliac veins applied to the Wallstent (Boston Scientific) and were not uniform. The new dedicated venous stents (Venovo from BD/Bard and Vici from Boston Scientific) are fundamentally different from the Wallstent in design, material, deployment accuracy, and radial force.2 There are no uniform guidelines on sizing of these stents, with operators’ experiences mostly gained from recent clinical trials. Intravascular ultrasound (IVUS) is considered the gold standard in sizing venous stents by most operators. Venography underestimates vessel size and lesion severity and cannot determine with accuracy the location of the compression, and therefore has been largely replaced with IVUS.3 Flow modeling by Ragu et al1 indicated that a common iliac vein (CIV) stent size should be at least 16 mm, external iliac vein (EIV) stent 14 mm, and common femoral vein (CFV) stent 12 mm. In one of their studies,4 an 18 mm Wallstent was deployed in the CIV followed by a 20 mm Gianturco Z stent (Cook Medical) at the upper end of the Wallstent. Postdilation was then performed with a 16 mm balloon. The Z stent can be protruded partially into the inferior vena cava (IVC) without the fear of stent thrombosis or jailing of the contralateral CIV. The authors reported that this resulted in a “modest self-limiting back pain” that occurred in about 25% of patients. None of the patients needed any long-term pain control and overall had good outcome on follow-up. Ragu et al1,4 generally upsize the stent by 2 mm above the recommended caliber, but postdilate the stent to the optimum outflow caliber of the segment, as described above.
Rossi et al5 presented data on iliac vein stenting with the Wallstent. They utilized stent diameters ranging from 16-22 mm and lengths of 60-90 mm. They used 16-20 mm balloons before and after stent deployment. They described a technical success rate of 100%, with a median stent diameter of 18.8 mm (range, 16-22 mm). Guided by IVUS, high pressure was used to obtain <20% residual narrowing on final imaging. Despite these large stents reaching up to 22 mm, 25% of patients had a transient back pain that was effectively and transiently treated with ibuprofen. In only 1 case, stent migration (IVC to iliac vein) occurred and was successfully treated by stent extension into the IVC.
We have recently advocated the use of the compression-spared segment of the ipsilateral CIV to obtain a reference luminal area or diameter by IVUS and size the stent accordingly.6 We have also oversized the stent by 1-2 mm when possible, as suggested by prior operators. Balloon dilation post stenting is generally limited to 16-18 mm balloons in the CIV. Our goal is to try to reach a minimum luminal area of >200 mm2 in the CIV post stenting. If the ipsilateral CIV stent is diffusely compressed, we recommend that the contralateral CIV be used to guide sizing, with selections no smaller than the minimum sizes outlined above by Ragu et al.1 The rationale to this sizing method is mainly to avoid lack of apposition of the stent to the CIV, which could potentially be a source of thrombosis, and to prevent stent migration. This is consistent with the utilization of the larger stents by Ragu et al4 and Rossi et al,5 with no complications reported other than transient pain that eventually resolved within a few weeks of the procedure.
We applied our sizing methods to the dedicated Venovo venous stent. In the first 27 consecutive patients enrolled at our center in the VERNACULAR trial (The Venovo venous Stent Study for Treatment of Iliofemoral Occlusive Disease; www.clinicaltrials.gov identifier NCT02655887), the Venovo stent yielded 100% technical success and 0% target-lesion revascularization at 1 year. Following market release of the stent, we treated an additional 23 patients for a total of 50 patients.7 Of the 50 patients enrolled, 1 reported worsening symptoms and progression of back and lower leg pain. We present this case and discuss in detail the anatomic and procedural characteristics.
The patient was a 41-year-old male (body mass index, 25.6 kg/m2) who presented with postthrombotic syndrome of the left leg with swelling and discomfort and lower back pain. He was in clinical, etiologic, anatomic, and pathophysiologic (CEAP) class III. He had history of pulmonary embolism, was a smoker, and had history of hyperlipidemia. He was on dabigatran for history of antiphospholipid antibody. He could not take warfarin, rivaroxaban, or apixaban because of headaches. After discussion of alternatives, risks, and benefits, the patient elected to proceed with venography and IVUS of the left leg and stenting as needed. The patient underwent his procedure. Venography revealed left to right iliac vein collaterals. Prestenotic dilation of the left CIV was seen on both venography and IVUS (Figure 1). Pretreatment minimal luminal area (MLA) in the ipsilateral non-compressed segment of left CIV (reference) was 320 mm2. The theoretical stent diameter was approximately 20 mm. The Venovo 20 x 60 mm stent was selected. The MLA at the confluent was 110 mm2 and the percent stenosis was calculated at 65.6%. Significant dense fibrosis was seen by IVUS at the compression site. The lesion was predilated at 14 atm followed by stent deployment. The stent was deployed accurately at the confluent with mild protrusion into the IVC. Postdilation was carried on with a 16 mm balloon at 12 atm. The MLA post stenting was 250 mm2, which was markedly improved and over the goal of 200 mm2 for optimal flow. There were no complications during the procedure. Post procedure, the patient had some back discomfort — which was not unexpected — and was given pain medications and discharged home the next morning.
The patient initially noted some improvement in his symptoms in the first 2 weeks post procedure. However, his back discomfort worsened afterward and he reported lower leg weakness and swelling. His presentation was very atypical, however, and was associated with multiple neurological symptoms, including slurred speech, headaches, weight loss, bradycardia, upper and lower arm pain, and hand tremors. Computed tomography of the head was negative. Magnetic resonance imaging of the spine showed some mild degenerative changes and mild foraminal narrowing at L4-5 not thought to be related to his pain. Evaluation at a university hospital did not reveal an explanation of his symptoms. Another opinion was obtained at another university hospital, where he also had an extensive work-up that failed to explain his symptoms. Neurologic testing was negative. He was thought to have “breakaway weakness” by the medical team. He was advised to undergo physical therapy to see if his symptoms would improve. However, he continued to have symptoms, with no objective evidence of neurologic impairment. Eventually, the decision was made to pursue removal of the stent considering the “complexity” of his “atypical” symptoms and the disabling back and lower leg pain. Stent explantation was then performed. The stent was noted to have a significant amount of hyperplastic tissue. In addition, protrusion of stent struts through the wall of the vein was noted during surgery. No bleeding was observed. Reconstruction of the iliac vein was performed with a vein graft. The patient did well post operatively. A few weeks after surgery, the patient noted that his leg and back pain were feeling better despite a repeat computed tomography angiography of the pelvis that showed recurrence of his iliac vein compression.
To our knowledge, this case illustrates the first Venovo venous stent that had to be explanted for presumed persistent back and leg pain, despite no evidence of neurologic or musculoskeletal injury and accurate positioning of the stent. The patient’s symptoms (by his report) improved following stent explantation a few weeks after surgery. It is unclear whether this was a placebo effect or a true improvement. He was seen at several high-quality academic centers and none could attribute his symptoms to the stent. In a recent case report from the Mayo Clinic, a 20 mm Wallstent that presumably caused back pain was explanted.8 This was explained by “caval extension” of the stent to the opposing wall of the IVC.9 The Wallstent is a much harder stent to position accurately given foreshortening during deployment, and it has been recommended that the stent be extended into the IVC. On occasion, it can become overextended during deployment and impinges on the opposing wall of the IVC when treating the stenosed confluent. In this patient, Rathore et al8 reported chronic and debilitating back pain following the stent placement. Both neurology evaluation and electromyography were also negative. The authors speculated that this pain was due to diffuse tissue tension in the vein wall and the surrounding structures caused by the oversized stents. It is unclear how “oversizing” of the stent was defined; oversizing is simply a misnomer without measuring the size of the vessel in which the stent would be deployed. This information was not clear in this case report. Also, the methodology of sizing the stent was not well defined by the authors. Of concern is the misleading concept of oversizing without a definition of optimal methodology to size the stent. Ragu et al4 and Rossi et al5 have used stents ranging from 16-22 mm almost routinely in their reported cases, with excellent outcomes and only mild and transient pain that resolved within a few weeks of the procedure. We strongly believe that IVUS can give a clear idea about the size of the iliac veins and help obtain optimal sizing as long as a minimum size is kept in mind to achieve optimal flow within the stent. Undersizing may lead to higher rates of restenosis and thrombosis, and possibly to stent migration. It may also create a more difficult problem to treat restenosis or thrombosis in the future. Since optimal stent sizing of a Venovo stent has not been well defined, we analyzed data from our first 50 patients treated with the Venovo stent to determine the size of the stents used and how this may relate to the occurrence of back and lower leg pain. To our knowledge, this is the first analysis to clarify this relationship of sizing with disabling pain post procedure with the new Venovo venous stents.
Size and Pain With the Venovo Venous Stent
We retrospectively reviewed the first 50 consecutive patients treated with the Venovo Venous stent for iliac vein compression at our center. In all patients, stent deployment and sizing were guided by IVUS, as previously described. Minimal luminal area (MLA) and minimal luminal diameter (MLD) at the compression and reference sites were measured by IVUS. The CEAP class was obtained on patients at baseline and at 30-day follow-up. The primary safety endpoint of freedom from acute venothromboembolic disease, stent migration, perforation, acute/subacute closure, and vascular complications was previously reported.7 Secondary endpoints included the patient-reported change in their symptoms of back and leg pain. This was graded as resolved, improved, unchanged, or worsened. The relationship between stent size and change in symptoms was analyzed.
A total of 50 consecutive patients (57 Venovo stents; 36 women and 14 men; mean age, 59.8 ± 16.3 years) were included. Twelve patients (24%) and 7 patients (14%) had history of deep vein thrombosis and pulmonary embolus, respectively. Smoking history and diabetes were present in 38% and 16%, respectively. Body mass index was 32.8 ± 9.0 kg/m2. Thrombophilia was present in 3 patients (6%). CEAP classes in the affected leg were II (6%), III (58%), IV (22%), healed ulcer (4%), and active ulceration (10%). Heaviness and pain in the affected lower leg were present in 74% of patients. Other symptoms in the affected leg included swelling in 86% of patients. IVUS-measured mean percent stenosis at the compression site was 64.8 ± 12.8%.
Mean stent length, diameter, and poststent balloon inflation pressures were 66.4 ± 28.8 mm, 17.1 ± 2.1 mm, and 8.0 ± 5.6 mm Hg, respectively. MLA before and after stenting was 64.4 ± 25.5 mm2 and 169.6 ± 40.4 mm2, respectively. Venovo stent diameters used were 14 mm (n = 7), 16 mm (n = 21), 18 mm (n = 22), and 20 mm (n = 22). Poststent minimal luminal diameter (MLD) at reference and compression sites was 17.2 ± 1.9 mm and 14.7 ± 1.7 mm, respectively. Postprocedure stenosis was reduced to 25.4 ± 12.8%. Procedural technical success was 100% (successful deployment with no intraprocedural complications). At 30-day follow-up, data on 48 patients were available. There was no target-lesion revascularization, 29 patients (60.4%) had improvement in pain symptoms, 16 patients (33.3%) had no pain, 1 patient (2.1%) had worsening pain, and 2 patients (4.2%) had unchanged pain compared with the procedure. Figure 2 displays the stent sizes and changes in pain symptoms.
Using Exact Chi-square test for independence, there was no statistical relationship between stent size of 20 mm vs <20 mm and leg or back pain (P=.08). In addition, there was no relationship between stent size of ≥18 mm and <18 mm (P=.34) and the pattern of pain change. Spearman’s correlation also showed no relationship between stent size and back or leg pain (Spearman Rho coefficient, -0.0210; P=.88).
There is no evidence that larger Venovo venous stent sizes lead to long-term back and worsening leg pain when sized according to IVUS measurements using the ipsilateral CIV reference area. Transient pain post CIV stenting typically resolves within 1 month post procedure. “Oversizing” or “undersizing” terms used to describe venous stents are meaningless with no predefined comparator reference diameter. There is no generally agreed upon stent-sizing method, but IVUS remains an important tool to give a more accurate reference diameter size and to assist in the choice of stent size. Although prestenotic dilation is likely to be present in the ipsilateral reference CIV, poststent balloon dilation of the confluent can be limited to 16-18 mm balloons, with the goal to accomplish an MLA of ≥200 mm2. Based on published data with larger Wallstents (≥18-20 mm) and our current data with the Venovo stent, the persistence of pain is unpredictable, exceedingly rare, and probably related to unknown individual patient factors.
From the Midwest Cardiovascular Research Foundation, Davenport, Iowa.
Disclosure: The author has completed and returned the ICMJE Form for Disclosure of Potential Conflicts of Interest. The author reports receipt of educational and research grants from BD/Bard, Boston Scientific, Philips, VentureMed Group, Angiodynamics, and Intact Vascular.
The author reports that patient consent was provided for publication of the images used herein.
Manuscript accepted May 12, 2020.
Address for correspondence: Nicolas W Shammas, MD, MS, FACC, FSCAI, Research Director, Midwest Cardiovascular Research Foundation, 1622 E. Lombard Street, Davenport, IA 52803. Email: firstname.lastname@example.org
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