We “still await” the ideal venous stent, despite rapid development in technology

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Today, venous stenting plays an important role in the treatment of deep venous pathologies. The current indications for the use of venous stents include acute iliofemoral thrombosis after catheter-directed or pharmacomechanical thrombolysis to resolve residual iliac stenosis, May-Thurner syndrome and the reopening of chronically occluded veins in patients with post-thrombotic syndrome, writes Athanasios D Giannoukas.

 

Two to four stents may be required and the stent should extend into the inferior vena cava, or also extend below the inguinal ligament inside the common femoral vein to allow free outflow from the deep femoral vein.

All venous stents used in venous pathologies are self-expandable stents. The first stent used in the early period was the Wallstent (Boston Scientific), which was not specifically designed for the venous system. The device provides good radial force because of its closed-cell design, but this comes at the expense of less flexibility. The available diameters and lengths are in the range of 10–16mm and 2–9cm, respectively. Zilver Vena (Cook Medical) is a new-comer and has been specifically designed for the venous system with open-cell design providing more flexibility and kink resistance. It is available in 14mm and 16mm diameters and in 6cm, 10cm and 14cm lengths. The Vici stent (Veniti) is another venous stent with closed-cell design with high crash resistance all the while maintaining good flexibility. This design was elected by the engineers of the company in order to provide greater coverage and support to vessel walls that have little smooth muscle of the tunica media. Optimed has recently launched a series of stents designed specifically for different venous territories: Sinus-XL, available from 16–36mm in diameter and from 3–10cm in length, which can be used in the inferior vena cava as well as the common iliac veins; Sinus-venous, with independent ring system and flash links providing power and flexibility for the iliac veins; and the most interesting new comer from the same company, Sinus-Obliquus, with a bevelled top end to be placed exactly at the confluence of the common iliac veins without protruding into the inferior vena cava.

Indeed, all the aforementioned evolution in venous stent technology over the last years has improved the performance of venous stenting opening up new horizons in the treatment. However, we are still quite a way from having available the ideal venous stent. The characteristics of the ideal venous stent could be summarised as follows:    

Should be deployed without foreshortening

Tapered

Have good visibility and flexibility

Be resistant to compression and high hoop strength

Be resistant to thrombus formation and platelet adherence

MR compatible

Have diameters 10–22mm and length 4–10cm

Be able to tolerate radius curvature of 2cm without protrusion of the metallic components of the cell structure inside the lumen

Be able to reach and retain the target diameter by balloon angioplasty

Beveled to be placed in the confluences/fenestrated

Be inexpensive  

In several studies there is a difference in the outcome of venous stenting between thrombotic and non-thrombotic pathologies. P Neglen and S Raju in their series reported 89% primary patency in non-thrombotic cases and 65% in the thrombotic cases in a three-year follow-up (Journal of Vascular Surgery 2002). Therefore, it appears reasonable to think that the “one size fits all” approach may not be applicable in venous stenting. Stents with specific designs may be needed to treat the entire spectrum of venous pathologies. Is this possible? From the evolution in stent technology which we have all witnessed in the arterial pathologies, for instance in the carotid territory with the introduction of stents with micromeshes and heparin bonding or in the femoropopliteal region with the drug-eluting stents and the vascular mimetic technology, it is realistic to expect similar advances in venous stents.

The prospect of an hybrid stent with a more rigid top end—to provide good radial force at the confluence of left common iliac to resolve the compression of the right iliac artery—and a more flexible distal part—to accommodate the needs of external iliac veins—is not unrealistic. Additionally, stents of open-cell design which will provide flexibility, with micromesh and heparin bonding or drug-eluting technology, could overcome the shortcomings of current stents used in acute thrombotic cases or chronically occluded veins, respectively.

As technology moves quickly and venous stenting gains popularity in the management of iliofemoral vein pathologies, advancements that may look like fantasy today may become a reality in clinical practice.

Athanasios D Giannoukas is professor of Vascular Surgery, Faculty of Medicine, University of Thessaly, Greece, chairman, Department of Vascular Surgery, University Hospital of Larissa, Greece, and secretary general of the European Venous Forum. He has reported no disclosures pertaining to this article.