Technique

Fenestrated EVAR stent grafting requires access through both femoral arteries. The procedure can be performed under general or regional anesthesia using an open femoral artery exposure or a percutaneous approach. The stent graft is a composite prosthesis based on the Zenith system (William A. Cook Australia, Brisbane, Australia), which has a self-expanding modular design with an uncovered Gianturco Z-stent (William Cook Europe, Bjaeverskov, Denmark) for proximal fixation in the standard configuration (Figure 1). The first part is a tube graft containing the fenestrations, the second part is a bifurcated device, and the third part is a contralateral limb extension. The tube graft containing the fenestrations is fitted with diameter-reducing ties. The diameter-reducing ties allow repositioning and reorienting of the graft after deployment to facilitate catheterization of the fenestrations and aortic branches.

Customization of the stent grafts is based on an individual anatomic configuration. Three types of fenestrations are possible: a scallop in the top of the graft, large fenestration with stent wires crossing, and small fenestrations. The most-used combination is two small fenestrations for the renal arteries and a scallop for the mesenteric artery (Figure 2). Each fenestration is marked by three (scallop) or four (small or large fenestration) radiopaque markers to enable accurate alignment (Figure 3). Each tube graft is fitted with anterior and posterior markers to facilitate orientation during insertion and deployment.

Complete deployment of the stent graft has to be carried out after catheterization of the small fenestrations and target vessels and secure positioning of a guiding sheath inside them. Stenting of small fenestrations, nowadays with covered stents, serves a purpose of sealing as well as optimal apposition between the fenestration with the ostium of each aortic branch. The covered stents are usually flaired with a 12 × 2 cm balloon to ensure encroaching on the reinforced fenestration, both for fixation and for sealing, and to facilitate recatheterization if needed at a later stage.

Limitations

Fenestrated EVAR aims at treating short-necked, pararenal, or suprarenal aneurysms. The standard graft has a scallop in the top of the fabric to include the superior mesenteric artery and two small fenestrations for the renal arteries, but other options are possible to match the specific anatomy of the patient being treated. Catheterization of the fenestrations as well as both renal arteries requires the possibility to reposition the graft until the fenestration and the renal artery ostium are in direct opposition. Any anatomy that precludes the repositioning process, such as small, calcified, or tortuous iliac arteries, and angulated or calcified proximal necks, can render the catheterization extremely difficult.

Anatomy precluding the introduction and patency of the inserted covered stents includes sharp takeoff and angulation of the renal arteries, as well as arteriosclerotic disease of the renal arteries. One has to recognize the risk of thromboembolic complications in the presence of mural thrombus at the level of the aortic side branches during repositioning of the graft. Aberrant anatomic variations including proximal origin of several visceral aortic branches can make it technically difficult or impossible to create a graft with multiple fenestrations. Length issues (too short, such as after previous stent grafting or open surgery with a short-body bifurcated graft) can create technical problems in using a composite system.

Obviously, proximal graft sealing and fixation are mandatory and a prerequisite for EVAR success. The graft should be planned to guarantee the first sealing stent of the tube graft to land completely inside the neck. If one cannot design the graft with two fenestrations and a scallop, one has to move to the next level, which includes three fenestrations and a scallop. This second-level graft is more difficult to plan, is more difficult to place, and requires better equipment because lateral fluoroscopy will be needed to catheterize and stent the superior mesenteric artery. In addition, the takeoff angle of the mesenteric artery often makes it necessary to reline the stiff balloon-expandable covered stent with a self-expandable stent to smooth the transition with the vessel and to avoid kinking of the balloon-expandable covered stent. Nevertheless, although the whole procedure takes longer in view of a third catheterization, the superior mesenteric artery is usually easy to catheterize from a femoral approach.

The next level would include four fenestrations, but this is rarely used because such a graft is difficult to design and even more difficult to execute. Indeed, the celiac artery is usually difficult to catheterize from a femoral approach, and the takeoff angle makes it tedious to insert a stiff covered stent. This type of graft is usually only needed in thoracoabdominal aneurysms, where grafts with directional branches rather than fenestrations are preferred.