A purely endovascular approach to TAAA repair can reduce the physiologic stress response to surgery, end-organ ischemia, and blood loss. However, these procedures require extensive preoperative planning and a thorough understanding of associated shortcomings and anatomical constraints. The introduction of low-profile devices in the past decade has allowed patients with smaller iliofemoral or brachial vasculature to be candidates for endovascular interventions and preloaded systems. Preloaded systems (wires and catheters) can shorten procedural times by providing direct access to branches and fenestrations.

As part of preoperative planning, three-dimensional CT angiography is utilized to assess proximal and distal landing zones, the anatomy of the aorta and target vessels, and patency of target vessels and spinal collateral networks; the anatomy of access vessels, including common femoral, iliac and brachial arteries, is also evaluated. Approved thoracic stent grafts require greater than or equal to 2 cm proximal seal zones. Three-dimensional workstations and imaging are also utilized intraoperatively in dedicated hybrid operating rooms to ensure accurate deployment of the aortic stent graft and its side branches while minimizing radiation exposure.

Paraplegia is a feared complication of both open and endovascular TAAA repairs. Hemodynamic instability that results in spinal cord infarction secondary to loss of intercostal arteries coupled with insufficient collateral network, microembolization from catheter or device manipulations, reperfusion injury, and spinal cord edema may be contributory. Although patent segmental arteries can be reimplanted during open surgical repair, these vessels are often too small to accommodate bridging stents. Staged segmental arterial occlusion is thought to allow rapid recruitment of the spinal collateral networks, which is the mainstay of strategies to reduce spinal cord ischemia in endovascular approaches. Staging can be performed using embolization of intercostal and lumbar arteries, temporary aneurysm sac perfusion, or the performance of TEVAR above the celiac artery for coverage of proximal intercostal arteries.

Position: Patients are supine with both arms raised overhead and the right axilla prepped in the event that brachial access is needed.

Surgical exposure and technique: Bilateral percutaneous femoral access is obtained. Open surgical exposure of the femoral arteries might be necessary if there is a high femoral bifurcation or the femoral arteries are small and calcified. Before the graft introducer is inserted into the arterial system, systemic anticoagulation with 100 U/kg of heparin is typically administered for a goal ACT greater than 200 seconds, although the goal may vary across institutions. Temporary iliac or femoral conduits can be used to facilitate early pelvic and lower limb perfusion in longer, complex cases. Most endovascular TAAA cases are performed using a total transfemoral approach, though some centers use brachial access to facilitate the procedure and minimize lower extremity ischemia. Fenestrated-branched endovascular stent grafts and off-the-shelf, multibranched devices, which are designed with four downgoing branches to incorporate the celiac axis, SMA, and renal arteries, are deployed in a staggered fashion. Precise graft positioning is facilitated by angiography in the setting of apnea. Once the stent grafts are deployed via the femoral approach, the target vessels are catheterized and stented, and the distal bifurcated device and iliac limb extensions are placed. Balloon dilation at seal zones and overlap zones between multiple grafts may be performed to ensure an adequate seal to the aortic wall. The LSCA may need to be covered by the endograft in order to achieve an adequate PLZ with the distal subclavian artery gaining perfusion from collateral vessels, including the left internal mammary artery and vertebral artery. If occlusion is not tolerated, a left carotid to subclavian bypass is performed.

Once the procedure is complete, contrast angiography is also used to evaluate for endoleaks and assess the integrity of the arterial system from the aorta to the iliac artery.

Limitations: Endovascular approaches have a steep learning curve for both physicians and centers. Proper development of technical strategies requires accurate measurements to ensure that the graft is an optimal fit, in addition to clinical experience to determine feasibility. Although intercostal arteries can be reimplanted during open surgical repair, they are often too small to be reconstructed endovascularly, which raises concern that extensive aortic coverage may increase the risk of spinal cord ischemia. In addition, extensive catheter and wire manipulations may lead to embolization of atheromatous debris and end-organ damage.

It is common for patients, especially females, to be ineligible for endovascular interventions based on anatomic criteria specific to devices. Use of endovascular devices outside of the manufacturer's instructions for use has been reported, though outcomes are controversial with evidence to suggest that nonadherence to these instructions is associated with higher rates of complications. Furthermore, custom-made branched and fenestrated devices are not available to patients in need of urgent or emergent interventions. Although chimney/snorkel grafts and standardized multibranched devices are options when TAAA repair is imminent, they may not be suitable for the repair of complex aneurysms extending above the visceral branches.

The need for relatively frequent reinterventions with total endovascular approaches, especially in patients with heritable thoracic aortic disease, is another shortcoming of TEVAR. This is, at least in part, why patients who undergo endovascular procedures require meticulous longitudinal annual surveillance. Imaging with CT angiography or duplex ultrasound is recommended annually after CT angiography is performed 1-month postoperatively; surveillance is indicated more frequently at 6-month intervals for patients with known type II endoleaks. Although many secondary procedures can also be performed using endovascular techniques, serious complications, such as expanding aneurysms, infection, fistula formulation, and aneurysm rupture, require open repair.