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Endovascular Treatment of Pararenal and Suprarenal Abdominal Aortic Aneurysms
Endovascular aortic aneurysm repair (EVAR) is now entering its third decade and has matured into a viable alternative to open repair. The mandatory need for a suitable proximal landing zone (also referred to as “the proximal neck”) was overcome about a decade ago with the introduction of fenestrated grafts. Vital branches, such as the celiac axis, superior mesenteric artery, and renal arteries cannot be sacrificed without a significant risk of end-organ ischemia. The proposed solution to this problem came with the customization of fenestrated stent grafts to incorporate these vital branches. First, short-necked infrarenal abdominal aortic aneurysms were addressed, quickly followed by pararenal and later suprarenal aneurysms. The further development of stent grafts with incorporated branches opened the way to the treatment of more complex thoracoabdominal aneurysms.
The technique using fenestrated stent grafts for pararenal and suprarenal aneurysms has matured and has been disseminated widely. Nevertheless, endovascular teams who want to introduce these techniques should be trained in selecting patients, choosing the appropriate graft, and executing the procedure. Although such training is provided by the manufacturer in cooperation with expert centers, it is difficult to judge when a team is ready to apply the technique without support. Even more difficult is to determine who should affirm the adequacy of training and competence of the new interventionists.
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.
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