Dr. Shammas comments on a case report and review by Plácido-Disla et al, entitled, "Iliac Vein Stent Migration to the Heart in Patients With Chronic Venous Insufficiency
Stent migration after common iliac vein stenting is rare but carries serious complications. There are several reports on cephalad iliac vein stent migration post deployment.1-3 Etiologies are not entirely clear but can be divided into 2 categories based on the time of occurrence:
a. Iatrogenic, intraprocedural due to advancing balloons or sheaths.
b. Late dislodgment following deployment, likely due to undersizing of the stent. However, other rare but possible reasons have been reported such as trauma,2 thigh massage therapy,3 and thrombus on the stent that leads to to flow impairment, prestenotic iliac vein dilation, and subsequent “sailing” of the stent forward.
Avoiding iatrogenic iliac vein stent migration is possible with careful monitoring of sheaths, balloons, and wires as they are advanced across a stented segment under fluoroscopy. The most important step is to avoid pushing against any resistance through the stent. Resistance can be met at the distal edge of the stent while advancing balloons or other catheters, at midstent in an underexpanded segment, or at proximal edge when balloons or wires are being pulled out.
Adequate sizing of the stent is also critical to avoid migration. The best method to size an iliac vein stent is unknown at this time. In our experience, we have sized these stents to the noncompressed ipsilateral common iliac vein (CIV). We typically measure the largest luminal diameter followed by measuring the luminal diameter midway and perpendicular to the largest diameter, and then we average these 2 numbers (Figure 1B). The stent is then chosen to be 1 to 2 mm larger than the calculated average.
If the ipsilateral CIV is all compressed, we do the sizing based on the contralateral noncompressed CIV using the same method. Another method we have successfully used is to measure the ipsilateral CIV reference area by intravascular ultrasound (IVUS) and determine the matching theoretical diameter of a circle (Table 1). The stent is then chosen with 1 to 2 mm larger diameter than the theoretical diameter obtained. Measuring the stent size based on computed tomography angiography (CTA) prior to the procedure to predict the stent to be used is likely to overestimate the size of the stent, as minimal luminal area obtained by CTA seems to be higher than what is measured by IVUS.4
The sizing methods above intend to obtain full apposition of the stent to the reference vessel. However, prestenotic dilation could lead to oversizing of the stent. It is unknown at this time whether oversizing can lead to adverse consequences. Reports indicate that pain in the low back may become more exaggerated post oversizing of the stent, but in our experience this tends to resolve in few days to a couple of weeks. However, rare reports in the literature indicate that the pain may become debilitating and chronic, requiring stent removal with surgery.5
On the other hand, it is unclear whether stent thrombosis increases with nonapposition of the stent. Also, it is unclear whether stent migration is increased in this situation. We believe that if stents are sized to the contralateral noncompressed iliac vein, and there is significant ipsilateral CIV prestenotic dilation, then stent length may need to extend to the proximal external iliac to avoid stent migration. Finally, it is unknown at this time whether vein wall remodeling would occur and eventually fully “hug” the stented segment. Veins are capacitance vessels, and it is possible that they may return to their original size when the obstruction is removed. At this time, and until more research is available on vein remodeling post stenting, we continue to be conservative in our approach of stent sizing, targeting the reference diameter of the noncompressed ipsilateral vein to achieve full stent apposition (Figure 1C).
Predilation of the confluent is critical and is best performed with a higher pressure at 8 to 12 atmospheres with a 1:1 balloon sized to the contralateral common iliac vein. Adequate analgesia is needed. Postdilation is best performed with same size balloon at a pressure yielding full balloon and stent expansion. The braided, self-expanding stainless-steel Wallstent (Boston Scientific), is currently being used and is likely to partially recoil at the confluent irrespective of balloon dilation because of weaker radial force. Newer venous dedicated stents (in various testing phases) may have better radial force and may be easier to deploy more accurately at the confluent. It is best to avoid protruding the stent into the inferior vena cava (IVC) if possible, but this is difficult to achieve with the Wallstent. Most operators favor protruding this stent into the IVC to avoid missing the confluent. However, data suggest that this approach may increase contralateral iliac vein thrombosis or pseudo-obstruction.6 This may not be an issue with the newer nitinol-based stents that do not seem to shorten with deployment and can potentially be deployed with accuracy at the confluent with minimal protrusion into the IVC. Postdilation is an important step to anchor the stent against the vessel wall and expand the minimal luminal area, and it should be routinely done to avoid stent migration.
In summary, operators may avoid stent migration with meticulous technique and appropriate sizing of stents. There may be unforeseen factors that contribute to stent migration. These are likely to be rare and need to be evaluated on a case-to-case basis.
The author has completed and returned the ICMJE Form for Disclosure of Potential Conflicts of Interest. The author reports research and educational grants with Boston Scientific and Bard.
Nicolas W Shammas, MD, EJD, MS, FACC, FSCAI, FSVM; President and Research Director, Midwest Cardiovascular Research Foundation, Davenport, Iowa, 52803. Email: email@example.com
1. Mullens W, De Keyser J, Van Dorpe A, et al. Migration of two venous stents into the right ventricle in a patient with May–Thurner syndrome. Int J Cardiol. 2006;110(1):114-115.
2. Hsiung MC, Chang YC, Wei J, et al. Embolization of the stent to the right heart after a motor vehicle accident. Echocardiography. 2010;27(5):587-589.
3. Haskal ZJ. Massage-induced delayed venous stent migration. J Vasc Interv Radiol. 2008;19(6):945-949.
4. Shammas NW, Shammas GA, Winter AR, et al. Imaging common iliac vein compression: differences between CT angiography, intravascular ultrasound and venography. Abstract #25. Presented at New Cardiovascular Horizons 2017, New Orleans, LA. http://www.ncvh.org/uploads/abstracts_11_1211204083.pdf. Accessed November 27, 2017.
5. Rathore A, Gloviczki P, Bjarnason H. Open surgical removal of iliac vein Wallstents with excision of pseudointima obstructing the contralateral iliac vein. J Vasc Surg Venous Lymphat Disord. 2016;4(4):525-529.
6. Murphy EH, Johns B, Varney E, Buck W, Jayaraj A, Raju S. Deep venous thrombosis associated with caval extension of iliac stents. J Vasc Surg Venous Lymphat Disord. 2017;5(1):525-529.