We assemble the stent graft in situ from three sets of components, or modules. The Zenith-based aortic components are categorized as thoracoabdominal or infrarenal, depending on their location. The thoracoabdominal component has one proximal orifice and multiple distal orifices, one for each visceral branch and one for the infrarenal aorta. The trunk and legs of the infrarenal aortic components are essentially the same as in a standard Zenith Trifab AAA system (Cook, Inc.). A small stent graft is used to extend each branch of the thoracoabdominal component into the visceral branches of the aorta; hence the term visceral extension.

The celiac and superior mesenteric branches of the thoracoabdominal component are cut from the same tube of fabric as the trunk. As a result, the segment below these branches is much narrower than the segment above, and there is space to work outside the stent graft, whatever the size of the aorta at that level. The trunk of the stent graft is oversized at least 4 mm relative to the supraceliac aorta. Visceral branch diameter and location vary according to the findings of pre-operative imaging. Nevertheless, thoracoabdominal components from different patients have been surprisingly alike, to the point where one could be substituted for another. Radioopaque markers on the trunk indicate axial orientation. Other markers at the outer ends of visceral cuffs guide the level of implantation, while markers around the inner ends guide catheterization. The thoracoabdominal component has a barbed uncovered proximal stent, like the standard Zenith abdominal aortic stent graft.

The infrarenal aortic components and the branch extensions have their own delivery systems. The delivery system for the thoracoabdominal component has the size (22 French) and proximal tip of the Zenith thoracic aortic device, and the shaft of the Zenith abdominal aortic device. Safety wires secure the proximal and distal ends of the stent graft to the central pusher of the delivery system.

The route from the brachial artery into the branches of the thoracoabdominal aorta is long and tortuous. We use a range of coaxial catheters to protect the aortic arch, prevent coiling, selectively catheterize the target arteries, and guide branch extensions into place. All those listed are manufactured by Cook, Inc. (Bloomington, IN). The large diameter (10-12 French) sheaths extend from the brachial artery into the
proximal end of the thoracoabdominal component. The smaller sheaths and guiding catheters fit inside the larger ones. The smaller sheaths have a range of tip configurations to help support the path from the cuff of the thoracoabdominal component to the branch artery. The 7 French catheters fit inside the small sheath and the guiding catheters. They are used for selective visceral artery catheterization. Once in place, they also serve as dilators for the surrounding sheaths. Long, small caliber catheters in a variety of tip configurations add another option for selective catheterization.

We used to use off-the-shelf sheaths, but we now have a range of Flexor sheaths specially made for this application. The outer sheaths are all 60 cm in length, and the inner sheaths are all 80 cm in length. The choice of sheath diameter depends on the type of covered stent being used as a branch extension. The lowest profile is the medium-sized JoMed, which can pass through a 7 French sheath. The largest JoMed requires an 8 French sheath, while the Fluency requires a 10 French sheath. Each inner sheath determines the minimum diameter of the corresponding outer sheath. If we stick to kink-resistant Flexor sheaths, the 7 requires a 9, the 8 an 11, the 9 an 11, and the 10 a 12.

The guidewires are all 35/1,000″ caliber and all are exchange length (>200 cm). Hydrophilic wires are used for primary catheterization. They are exchanged for stiffer Rosen-tip wires.

All the important steps in the procedure are image-guided, and the advantages of high-quality imaging in an interventional suite probably outweigh the advantages of overhead lighting and sterility in an operating room. It is possible to implant a multibranched stent graft using a mobile C-arm, but it is wise to have another in reserve in case of overheating.

We currently prefer the balloon-expanded PTFE-covered JoStent as a visceral extension. The diameter depends on the size of the target artery. JoStents that are 58 mm long are delivered on 6 cm-long 5 French balloons.

Our technique has evolved over the past 4 years to reflect the lessons of our experience with this approach (see below), but the basic elements remain the same. Sometimes it is easiest to insert the extensions before inserting the abdominal components, as depicted in Figures 15-1, 15-2, 15-3, 15-4, 15-5, 15-6, 15-7; sometimes the reverse is true, as described below.

Our technique is the following: