Endovascular thoracic and TAAA repair is most often performed using access via one or both iliofemoral arteries. For complex procedures involving fenestrated and branched
endografts, brachial access is also needed. Difficulties in gaining access remain an obstacle to TEVAR. Most problems can be anticipated based on review of preoperative imaging. An adequate CTA study should evaluate the abdominal aorta, iliac arteries, and common femoral arteries distal to the bifurcation. Presence of small iliac artery diameter (<8 mm), severe calcification, stenosis or occlusion, excessive tortuosity, or dissection may preclude safe introduction of large delivery systems (>20 Fr), which is needed for most commercially available thoracic and TAAA endoprosthesis using conventional femoral approach.

Selection of the ideal access is individualized and takes into consideration iliac artery diameter, occlusive disease, tortuosity, prior stents, or surgical grafts. For most operators, right iliac artery is favored, but these procedures can be safely performed through either approach. The contralateral femoral is accessed using a small 5- or 6-Fr sheath for introduction of angiography catheters for diagnostic purposes. TAAA repair requires bilateral femoral access for placement of renal fenestrated-branches and a distal bifurcated device.

If difficult access is encountered or anticipated, several maneuvers are recommended to avoid iliac artery disruption. Open surgical or endovascular conduits are required in approximately 10% to 15% of patients. Open surgical conduits are performed either prior to the procedure (permanent iliofemoral conduit) or in conjunction with the endovascular repair. A staged permanent conduit should be considered in patients requiring TAAA repair with fenestrated and branched endografts because of the coagulopathy that frequently occurs following these procedures; it should also be considered in patients who have aortic disease affecting multiple segments, where multiple repairs are anticipated. These procedures are performed using a lower abdominal curvilinear incision to enter the retroperitoneum. Blunt dissection is carried over the psoas muscle and iliac crest, exposing the common, internal, and external iliac arteries. After these vessels are controlled with sylastic vessel loopes and the patient is heparinized, a longitudinal arteriotomy is made from the distal common iliac artery to the external iliac artery. The authors’ preference is to use a 12-mm polyester graft, anastomosed in an end-to-side fashion using 4-0 prolene suture with “parachute technique.” This graft diameter allows adequate room for introduction of 24-Fr delivery system with no difficulty. If a permanent conduit is planed, the authors’ preference is to bevel the external iliac artery and anastomose the graft end-to-end carrying the anastomosis to the distal common iliac artery. The distal anastomosis is done to the proximal common femoral artery under the inguinal ligament via a separate longitudinal groin incision.

The endoconduit technique is also an excellent alternative in patients with occlusion of the ipisilateral internal iliac artery. Because this technique requires coverage of the internal iliac artery, we do not recommend its use in patients with patent internal iliac arteries who need coverage of extensive thoracic or TAAA segments. The endoconduit or “paving and crack” technique applies use of small profile peripheral stent grafts or covered stents from the common iliac artery to the distal external iliac artery, with subsequent forceful dilatation to enlarge the vessel to 10 or 12 mm. It is critical that adequate proximal and distal seal is achieved to avoid uncontrolled arterial bleeding.

Brachial access is needed routinely for most TAAAs using a 10- or 12-Fr sheath (Fig. 29.1). The authors’ preference is to perform ultrasound of the proximal brachial artery just distal to the axillary hairline. If the brachial artery measures >4 mm in diameter, the vessel is surgically exposed for direct access. If smaller, the axillary artery is exposed in the delto-pectoral groove or via infraclavicular incision. Branch incorporation with directional branches is typically done via the brachial artery using a coaxial system with 12-Fr sheath and either a 9-Fr sheath (Fluency stent graft) or 7-Fr sheath (Viabahn or iCAST stent graft). For these cases the patient is positioned with the left arm abducted (Fig. 29.1), which facilitates access and minimizes radiation exposure to the operator, who can work away from the imaging intensifier. Alternatively, in patients where only one branch is performed via brachial access using a 7 or 8 Fr sheath, the distal brachial artery can be accessed at the antecubital crease. The authors’ preference is to routinely surgically expose the brachial artery for repair, eliminating risk of puncture hematoma, and its associated nerve injury.

The presence of a healthy proximal and distal sealing zone is of paramount importance to achieve successful and durable aneurysm exclusion. The proximal and distal landing zones must be selected in “normal aortic segments,” defined by parallel aortic wall, with minimal or no thrombus or calcification. The minimum length is >2 cm. Longer lengths are needed in tortuous segments such as in the aortic arch, or in patients with familial history of aortic disease, ectasia or thrombus laden aorta. Because it is critical to assure 360-degree apposition between the stent-graft fabric and aortic wall, this requirement is not compromised to achieve a durable result. One should not be tempted by acute successes, which are more often tempered by late endoleaks in patients with difficult anatomy who do not meet basic anatomical requirements. For this reason, if there is not an adequate sealing zone in the distal thoracic aorta or arch, other techniques of branch vessel incorporation (debranching, branched, or parallel grafts) should be contemplated.

The aortic arch has been divided into four zones proposed by Ishimaru, based on the location of the landing zone in relation to supra-aortic trunks. One should not underestimate length of sealing zone if the intended stent grafts will be placed in zones 0 to 3. In these cases, one should plan for additional length for optimal apposition of the stent graft in the innercurvature of the aortic arch. Although recent technologic improvements in device conformability have facilitated these repairs, there are many challenges in the arch; to name a few, proximity to the aortic valve, acute angulation, supra-aortic trunks, hemodynamic forces, and respiratory motion.

Open surgical debranching has been widely applied in patients with aneurysms encroaching the carotid or subclavian arteries. Although coverage of the subclavian artery has been advocated by some, most agree that patients with extensive thoracic and thoracoabdominal aortic aneurysms need subclavian artery revascularization to minimize rate of spinal cord injury. The authors’ preference is to use a carotid–subclavian bypass or transposition done in single stage combined with stent-graft placement. If the intended
landing zone is in zone 1, a carotid–carotid bypass and carotid–subclavian bypass can be done. Description of arch branch devices is beyond the scope of this chapter, but these devices are already available and will limit the need for debranching procedures. Finally, for proximal arch involvement requiring placement of stent graft in zone 0, a decision is made between the options of aortic-based arch debranching or conventional arch replacement with frozen elephant trunk technique. The later provides an excellent landing zone for endograft placement.

Extension of the aneurysm into the visceral segment defines TAAA pathology and therefore requires incorporation of the celiac axis, superior mesenteric artery (SMA) and renal arteries. A more detailed analysis with centerline of flow and axial measurements is used for accurate sizing. Although limited repairs with one or two vessels (e.g., celiac and SMA) can be planned, more often a four-vessel repair is recommended with extension of the landing zone to the infrarenal segment. Aortic side branches requiring incorporation should also be analyzed for presence of occlusive disease, excessive calcification or thrombus, unusual or aberrant anatomy. Small sized, calcified, or multiple renal arteries pose a challenge. If an endovascular technique is selected to incorporate a side branch, special attention should be taken to side branch anatomy, vessel tortuosity, adjacent thrombus, or occlusive disease. Independent of which technique is utilized to treat the visceral artery, anatomical factors may significantly impact technical difficulties and method of reconstruction.

Hybrid approach or surgical debranching was introduced as a less-invasive alternative to open conventional repair. The first report was by Quinones–Baldrich and associates from UCLA in 1999. The operation aimed to reduce the anatomic and physiologic stress to the patient by avoiding several shortcomings of open surgery: Thoracotomy, single lung ventilation, aortic cross clamping, and prolonged end-organ ischemia. The early enthusiasm with surgical debranching has been tempered by several reports, which demonstrated significant risk of mortality and morbidity, particular when hybrid procedures are indicated in elderly patients with high surgical risk. Therefore, its current role in the treatment of patients with complex aortic aneurysms has evolved, and most centers with easy access to fenestrated and branched endografts have relegated hybrid procedures to high-risk patients who are neither candidates for total endovascular repair or open surgery. Patient selection, case planning, and technical aspects of the procedure are key for successful outcomes. If debranching is considered, the quality of the inflow site, which is typically located in the distal common and proximal external iliac artery, should be reviewed for presence of occlusive disease. It is critical to assure optimal inflow to the visceral grafts and enough length within the common iliac artery for attachment of the endografts. The presence of any abnormal venous anatomy (e.g., left-sided vena cava, retroaortic renal vein, etc.) should be noted to avoid inadvertent injury. For debranching procedures, thoracic and abdominal stent grafts are utilized for the endovascular portion of the procedure.

Total endovascular incorporation can be done using either parallel stent grafts or fenestrated and branched stent grafts. Snorkel and chimney grafts have been used in select centers, but endoleak rates are higher in systematic reviews, approaching 5% to 10%. The parallel stent graft is constructed using either a balloon-expandable or self-expandable stent, preferentially
a covered stent, placed between the aortic wall and the main aortic stent graft to preserve flow into the target vessel. Variations of this technique depending on stent configuration have been named periscope, sandwich, snorkel, and chimney grafts. Long-term result is still lacking and concern remains about the fate of “gutter” endoleaks and the durability of longer branches (e.g., “sandwich grafts”), which are often required in patients with TAAAs. These techniques have a role in the emergency setting or as a bail out in the event of inadvertent side branch coverage during conventional endovascular repair.

The use of fenestrations and directional branches makes logical sense, given that these devices have been specifically designed to incorporate side branches and follow basic engineering principles to assure adequate seal. The current worldwide experience with manufactured devices uses the Cook Z stent platform. TAAA stent-graft design includes one of two options. An off-the-shelf multibranch stent graft (t-Branch, Cook Australia) pioneered by Tim Chuter from UCSF includes four downgoing directional branches (Fig. 29.2) intended to be accessed via brachial approach and bridged to the target vessel by self-expandable stent grafts. Directional branches are optimal for downgoing vessels which originate from a large aneurysm sac, where there is significant gap between the aortic stent graft and the aortic wall. Alternatively, a custom-made option (Fig. 29.2) is also available which requires a time delay of 6 to 8 weeks for manufacturing in Brisbane, Australia. These devices can have any combination of branches and fenestrations to fit the patient’s anatomical needs. Because the renal arteries are often transversely oriented or upgoing and have smaller size diameter, the use of downgoing branches is often not ideal. In these cases, a fenestrated device or combination of branches for the celiac axis and SMA with two fenestrations for the renal arteries is utilized. Fenestrations are the preferred method of incorporation for vessels that originate from narrow aortic segments, such as frequently observed with chronic dissections and type IV TAAAs.