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Bridging Devices in Complex Endovascular Aneurysm Repair


Numerous bridging devices have been used in patients undergoing complex endovascular aneurysm repair (EVAR) with involvement of one or more target vessels. In this chapter we highlight the most common bridging devices and outline their strengths and limitations, as used in the Department of Vascular Surgery at St. Franziskus Hospital Münster, Germany.

Stainless Steel Balloon-Expandable Covered Stents

The Advanta/i-Cast V12 (Maquet) was designed based on the polytetrafluoroethylene (PTFE) film–covering technology. The 316L stainless steel struts are completely covered on their luminal and abluminal surfaces, protecting both the flow lumen and the wall from contact with the struts. In addition , the double coverage prevents disconnection of the stents struts from the PTFE material, preventing injury or dissection of the target vessels. The open-cell design facilitates safe advancement through sheaths, particularly in an angulated descending aorta, minimizing the risk of stent loss from the balloon. This complication was reported in the past, since the first-generation covered stents had a closed-cell design.

Fig. 17.1 shows the stainless steel balloon-expandable covered stent (BECS). The length of covered stents in fenestrated/branched (f/b-EVAR) and chimney (ch-EVAR) endovascular repair varies from 22 to 38 to 59 mm. The devices are compatible with a 7-French (7F) sheath and have diameters ranging between 5 and 8 mm.

FIG. 17.1, Advanta/i-Cast balloon-expandable covered stent.

Features

Key features include radial force and fluoroscopic visibility.

Radial force

The radial force of the bridging devices plays an important role. High radial force is essential to maintain long-term patency when bridging devices are used parallel to and outside of abdominal or thoracic devices. Computed tomography angiography (CTA) shows the ideal conformability of the Endurant device around the three balloon-expandable chimney grafts. The covered stents are completely expanded, achieving the intended nominal diameter without compression. Such observations make stainless steel BECSs the first choice in the chimney technique, particularly in combination with the Endurant abdominal stent-graft system.

Fluoroscopic visibility

Good fluoroscopic visibility is the next important feature which characterizing the Advanta BECS ( Fig. 17.2A ). The proximal and distal edge of the device can be easily identified during the procedure, especially when the operation is performed in a hybrid angiosuite with advanced imaging equipment. Adequate imaging is imperative for precise positioning of the covered stent.

FIG. 17.2, A, Proximal and distal edges of the balloon-mounted covered stent. B, Ideal placement of the chimney graft in the middle of the suprarenal stent of the aortic endograft.

Adequate fluoroscopic visibility plays an important role when the Advanta covered stent is deployed in conjunction with the Endurant stent-graft in a parallel chimney configuration. The goal is to deploy the device in the middle of the suprarenal stent of the endograft ( Fig. 17.2B ). Fig. 17.3 shows the potential risk for interaction and cutting of the balloon from the pins of the suprarenal stent of the Endurant device.

FIG. 17.3, Pins of suprarenal stent of Endurant device. The pins have the potential to cut the balloon of the chimney graft and provoke an uncontrolled interaction between the abdominal device and graft.

Limitations

The balloon-expandable devices are rigid. In angulated renal arteries, this rigidity requires lining with additional, self-expanding, flexible nitinol stents to improve the transition of the device. Fig. 17.4 illustrates the smooth transition of the BECS in angulated anatomy after lining with deployment of a nitinol bare-metal stent.

FIG. 17.4, Combined placement of balloon-expandable chimney covered stent proximally and a self-expanding nitinol bare-metal stent distally in the renal artery, achieving a smooth transition of the chimney graft in an angulated renal artery.

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