INTRODUCTION — Endovascular repair of the thoracic aorta, also referred to as thoracic endovascular aortic repair (TEVAR), refers to a minimally invasive approach that involves placing a stent-graft in the thoracic or thoracoabdominal aorta for the treatment of a variety of thoracic aortic pathologies. TEVAR was initially used to provide treatment to patients who were not considered to be surgical candidates, but it is now the preferred technique for treatment given the improved risk profile compared with open thoracic aortic surgery. In this topic review, we principally discuss endovascular repair of thoracic aortic aneurysm, but variations on the technique as it pertains to other thoracic pathologies are also briefly reviewed.

The indications for, preparation, and issues related to thoracic endograft placement, follow-up, and outcomes will be reviewed. Issues related to the management of thoracic aortic diseases that might be treated using thoracic endovascular stent-grafts are discussed separately. (See "Management of thoracic aortic aneurysm in adults" and "Management of acute type B aortic dissection" and "Clinical features and diagnosis of blunt thoracic aortic injury" and "Overview of acute aortic dissection and other acute aortic syndromes" and "Management of blunt thoracic aortic injury".)

Anesthetic issues regarding endovascular aortic repair are reviewed separately. (See "Anesthesia for endovascular aortic repair".)

ANATOMIC CONSIDERATIONS — Aortic arch anatomy, extent of aortic arch disease (figure 1), and the available landing zones dictate the nature of endovascular repair.

"Normal" thoracic aortic diameter varies according to location within the aorta and also with age, gender, and body habitus [1-3]. Average normal diameters of the thoracic aorta identified on imaging (computed tomography, magnetic resonance) are given elsewhere. (See "Clinical manifestations and diagnosis of thoracic aortic aneurysm", section on 'Definition of TAA'.)

Aortic anatomy — The aorta originates immediately beyond the aortic valve and ascends initially, then curves, forming the aortic arch, and descends caudally adjacent to the spine. The ascending thoracic aorta gives off the coronary arteries, and the aortic arch branches are typically the brachiocephalic trunk (branches to the right common carotid and right subclavian arteries), left common carotid, and left subclavian arteries; however, aortic arch anatomy can vary (figure 2). The descending thoracic aorta provides paired thoracic arteries (T1-T12) and continues through the hiatus of the diaphragm (figure 3A-B) to become the abdominal aorta, which extends retroperitoneally to its bifurcation into the common iliac arteries at the level of the fourth lumbar vertebra.

The abdominal aorta is a retroperitoneal structure that begins at the hiatus of the diaphragm and extends to its bifurcation into the common iliac arteries at the level of the fourth lumbar vertebra (figure 3B). It lies slightly left of the midline to accommodate the inferior vena cava, which is in close apposition. The branches of the aorta (superior to inferior) include the left and right inferior phrenic arteries, left and right middle suprarenal arteries, the celiac axis, superior mesenteric artery, left and right renal arteries, possible accessory renal arteries, left and right gonadal arteries, inferior mesenteric artery, left and right common iliac arteries, middle sacral artery, and the paired lumbar arteries (L1-L4).

The common iliac artery bifurcates into the external iliac and internal iliac arteries at the pelvic inlet (figure 4). The internal iliac artery, also termed the hypogastric artery, gives off anterior and posterior branches to the pelvic viscera and also supplies the musculature of the pelvis. The external iliac artery passes beneath the inguinal ligament to become the common femoral artery.

Landing zone classification — The thoracic aorta is divided into landing zones (zones 0 to 4) for the purpose of describing the extent of endovascular coverage, which determines the need for aortic debranching procedures (figure 5). For each of these, the endograft attachment site can be described as below with the proximal attachment zone classified as Zone 0 to 5 and the distal attachment zone classified as Zone 4 to 11 [4]:

●Zone 0 – Proximal to the innominate artery origin

●Zone 1 – Distal to the innominate but proximal to the left common carotid artery origin

●Zone 2 – Distal to the left common carotid origin but proximal to the subclavian artery

●Zone 3 – ≤2 cm from the left subclavian artery without covering it

●Zone 4 – >2 cm distal to the left subclavian artery but within the proximal half of the descending thoracic aorta (T6)

●Zone 5 – Starts in the distal half of the descending thoracic aorta but proximal to the celiac artery

●Zone 6 – Celiac origin to the top of the superior mesenteric artery

●Zone 7 – Superior mesenteric artery origin, suprarenal aorta

●Zone 8 – Covers at least one renal artery

●Zone 9 – Infrarenal

●Zone 10 – Common iliac

●Zone 11 – External iliac

Spinal perfusion — The spinal cord is supplied by three major vessels arising from the vertebral arteries in the neck, one anterior spinal artery and a pair of posterior spinal arteries, which anastomose distally at the conus medullaris (figure 6). The anterior spinal artery supplies the anterior two-thirds of the spinal cord. The thoracic spinal cord is particularly dependent on radicular contributions to the anterior spinal artery. The artery of Adamkiewicz (Arteria Radicularis Magna) is the most prominent thoracic radicular artery and can be found between the T9 to T12 level in the majority of individuals but can also be located above or below this level. The anatomy of the spinal cord is discussed in more detail elsewhere. (See "Spinal cord infarction: Epidemiology and etiologies", section on 'Vascular anatomy' and 'Minimizing spinal ischemia' below and 'Spinal cord ischemia' below.)

INDICATIONS FOR ENDOVASCULAR AORTIC REPAIR — Endovascular repair of the thoracic aorta was initially used to provide treatment to patients with thoracic aortic aneurysm who were not suitable candidates for open surgery. The pivotal trials of stent-graft placement for the treatment of thoracic aortic aneurysm led to its approval by the US Food and Drug Administration (FDA) in 2005 [5-10]. Endovascular repair of the thoracic aorta has been increasingly used for other aortic pathologies, including blunt thoracic aortic injury, aortic dissection, and penetrating aortic ulcer, among others [11,12]. Guidelines from major medical and surgical societies emphasize an individualized approach when choosing endovascular repair, taking into account the patient's age and risk factors for perioperative morbidity and mortality. Whether to choose an open or endovascular approach for specific aortic pathologies is discussed in separate topic reviews. (See 'Thoracic aortic aneurysm' below and 'Other thoracic aortic pathologies' below.)

While there are no randomized trials directly comparing open and endovascular repair of the thoracic aorta, observational studies suggest equivalent or better patient-important outcomes with thoracic endovascular repair [13]. Benefits of endovascular relative to open repair include avoidance of sternotomy and thoracotomy, no need to cross-clamp the aorta, less blood loss, a lower incidence of end-organ ischemia, fewer episodes of respiratory dependency, and quicker recovery [14].

Thoracic aortic aneurysm — Degenerative thoracic aortic aneurysms are classified depending upon their proximal and distal extent as ascending aneurysm, arch aneurysm, descending thoracic aneurysm, and thoracoabdominal aneurysm (figure 1) [1,15-18]. These categories help to stratify the approach to surgical management. (See "Management of thoracic aortic aneurysm in adults".)

Patients with thoracic aortic aneurysms, particularly large or expanding aneurysms, have an overall poor prognosis. Survival is improved for open surgical repair compared with medical therapy, and although there are few data comparing endovascular repair and medical management, it is reasonable to assume that outcomes will also be better for endovascular repair in those patients with indications for open surgery, since endovascular repair compares favorably with open surgery. (See "Management of thoracic aortic aneurysm in adults".)

Although endovascular repair of infected aortic aneurysm is not the preferred treatment, it is an option for patients who are poor surgical candidates [19-21]. These issues are discussed in detail and summarized elsewhere. (See "Overview of infected (mycotic) arterial aneurysm".)

Other thoracic aortic pathologies — Because endovascular repair is associated with a significant reduction in perioperative morbidity and mortality compared with open surgical repair, an endovascular approach is increasingly being applied to a variety of thoracic aortic pathologies, including blunt thoracic aortic injury, aortic dissection, aortic intramural hematoma, and penetrating aortic ulcer, among others [11,12].

Blunt thoracic aortic injury — Traumatic aortic transection typically occurs with high-speed, deceleration-type injuries at the level of the ligamentum arteriosum. Endovascular repair has been associated with significantly lower perioperative morbidity and mortality compared with open repair [22-24]. Systemic anticoagulation can be held during these cases if there is concomitant head injury [25]. However, long-term data regarding the longevity of stent repair in this typically younger age group are not available. (See "Surgical and endovascular repair of blunt thoracic aortic injury".)

Aortic dissection — The treatment of acute, uncomplicated aortic dissection is primarily conservative, but intervention may be needed for those who develop complications. Treatment of complicated Type B dissection with malperfusion has been successfully treated using endovascular techniques and consists of covering the primary entry tear and re-expanding the true lumen [26,27]. Assessment of the restoration of luminal flow to the true lumen can be performed with the use of IVUS (intravascular ultrasound), which offers real-time information regarding the true and false lumina throughout the cardiac cycle. Although thoracic devices have been approved by the US FDA for the management of both acute and chronic dissection, there is considerable uncertainty in terms of the role of thoracic endovascular aortic repair (TEVAR) in the setting of chronic dissection, and further study is needed.

In the multicenter INvestigation of STEnt grafts in patients with type B Aortic Dissection (INSTEAD trial), optimal medical therapy was compared with endovascular stent-graft placement [28,29]. At one-year follow-up, no significant difference in all-cause mortality was found between the groups. At five years, TEVAR in addition to optimal medical treatment was associated with improved aorta-specific survival and delayed disease progression. A critique of the INSTEAD trial was that the study was designed to evaluate patients with more chronic dissections (56 days in the stent-graft group versus 75 days in the medical management group). The ADSORB study, a pending trial in Europe, will compare best medical management to stent-grafting for patients with uncomplicated type B dissection presenting <14 days after symptom onset [30]. (See "Surgical and endovascular management of acute type B aortic dissection" and "Surgical and endovascular management of acute type A aortic dissection".)

Aortic intramural hematoma/penetrating aortic ulcer — These lesions are within the spectrum of aortic dissection pathology, and endovascular treatment is similar to type B aortic dissection, consisting of covering the intimal tear of any coexistent dissection to exclude the aortic lesion. Although isolated penetrating ulcers are easier to cover with endovascular devices, extensive intramural hematoma may be a contraindication to this approach. (See "Overview of acute aortic dissection and other acute aortic syndromes".)

Aortoesophageal fistula — Aortoesophageal fistula is a life-threatening cause of upper gastrointestinal bleeding that may be due to a variety of etiologies (eg, malignancy, thoracic aneurysm, foreign body including aortic stent-graft) [31]. Endovascular stenting may be used as a temporizing measure to prevent exsanguination and allow for fluid resuscitation [32,33]. Patients are at risk for graft infection if definitive esophageal repair is not performed. In one retrospective review, endovascular stent-grafting was performed within 24 hours of diagnosis in 83 percent of patients and was technically successful in 87 percent [32]. Open graft explantation and resection and repair of the esophagus constitute definitive repair [34] and in this series was able to be performed within one month of presentation in 11 percent of patients.

Contraindications — Endovascular repair of the thoracic aorta is contraindicated in patients who do not meet the anatomic criteria required to place any of the available endografts. (See 'Planning TEVAR' below and 'Choice of endograft and endograft sizing' below.)

Whether young patients, typically those suffering traumatic aortic injury, who have an acceptable risk for open surgery should undergo endovascular repair remains controversial. Surveillance over an extended period of time exposes the patient to greater levels of cumulative radiation, and long-term outcomes are unknown.

A relative contraindication to endovascular repair is the inability to comply with the required follow-up surveillance. (See 'Postoperative endograft surveillance' below.)

THORACIC ENDOGRAFTS — Endovascular repair of thoracic aortic aneurysm is accomplished using a fabric-covered stent, termed an endograft or stent-graft. Adoption of stent-graft technology by vascular surgeons has been rapid, primarily related to preexisting experience and facility with the endovascular repair of abdominal aortic aneurysm. (See "Endovascular repair of abdominal aortic aneurysm".)

Although there are variations from device to device, three components (delivery system, main body, and extensions) are common to all endograft device systems. Thoracic endograft devices are currently approved for treatment of descending thoracic aneurysms, penetrating aortic ulcers, aortic intramural hematoma, descending (type B) thoracic aortic dissection [35,36], residual descending thoracic aortic dissections, and traumatic aortic transection [37] in the United States [38,39].

Thoracic endovascular devices for thoracic aortic repair are discussed in detail elsewhere. These include (see "Endovascular devices for thoracic aortic repair"):

●TAG and cTAG

●TX2 and Alpha

●Valiant Thoracic Stent-Graft system

●Relay

The degree of structural support varies from device to device. Proponents of designs that have less metallic support structure claim the device is better able to adapt to changes in aneurysm configuration over time. On the other hand, some physicians feel that fully supported endografts are less prone to kinking and subsequent thrombosis. The curve of the proximal thoracic aorta adds an additional challenge to achieving a design with adequate proximal fixation and seal. The amount of radial support, which allows the endograft to withstand external compression, must be weighed against the need for enough flexibility and conformability within the device to navigate the proximal aorta and achieve a proper seal following deployment.

New endograft designs are continually being tested to enhance performance. Improvements have focused upon smaller device and delivery profiles, more accurate deployment, improved fixation systems, and perhaps most importantly, flexibility in managing challenging anatomy. These improvements, along with increased operator experience, have led to improvements in the short-term and long-term results of endovascular aneurysm repair and have expanded the application of endovascular repair to many patients whose aortic anatomy was previously deemed unsuitable.

PLANNING TEVAR

Choice of imaging — We prefer computed tomography angiography (CTA) of the chest, abdomen, and pelvis, including the femoral arteries, and three-dimensional reformatting to assess the aorta to appropriately size the diameter and length of the thoracic endograft. CTA provides accurate information regarding the external and endoluminal diameter of the aorta at the proximal and distal seal zones, the length of aortic coverage needed, the degree of angulation and tortuosity of the aorta (which may identify the risk for endoleak [40]), identification of important side branches, as well as characteristics of the lumen and wall of the aorta, including thrombus burden and calcification.

Magnetic resonance angiography (MRA) can also be used, but MRA does not demonstrate vessel wall calcification, which has implications for vascular access [41].

Aortoiliac evaluation — Imaging evaluation of the aorta involves measurement of the external or endoluminal diameter of the aorta at the proximal and distal seal zones, identifying the length of aortic coverage needed, the degree of angulation and tortuosity of the aorta, identification of important side branches, as well as evaluating the characteristics of the lumen and wall of the aorta, including thrombus burden and calcification. We use centerline measurements, which are particularly useful for angled sections of the aorta, to evaluate for device length, but other methods are also used [42,43]. The angulation of the aorta often progresses with age as atherosclerotic changes lead to lengthening and increased tortuosity, which adds to the difficulty of accurate device deployment and obtaining an adequate proximal seal. In general, a 2-cm length of normal diameter aorta is required to achieve a seal. Specific parameters for individual devices are given in the instructions for use (IFU) for each device.

Suitable iliac artery morphology is also required for passage of the thoracic endograft. The iliac arteries should have a minimal amount of calcification and tortuosity, and no significant stenosis. Generally, a 7- to 8-mm external iliac artery should accommodate a 22 French sheath, which is an approximately 24 French (8-mm) outer diameter. In one review, women were more likely to require a low-profile device or conduit to allow placement of a device [44]. The requirements for a specific device are found in the IFU. Once the diameter of the iliac and femoral arteries and the degree of calcification/tortuosity are evaluated, a decision can be made as to whether to proceed with transfemoral or alternative access. (See 'Vascular access' below.)

Zones of attachment — To exclude blood flow from a thoracic aortic aneurysm sac, the endograft must provide an adequate seal where the endograft contacts the arterial wall proximally at the aneurysm neck and distally, otherwise known as the landing zones. Compared with endograft placement in the abdominal aorta, the high forces in the thoracic aorta require longer seal zones (2 cm) to prevent displacement.

●Proximal – The proximal landing zone may abut or involve branch vessels of the arch, namely the brachiocephalic trunk, left common carotid artery, and left subclavian artery. When device deployment is performed close to or within the arch, the graft must closely appose the "inner curve" of the arch. If the proximal end of the graft is oriented toward the apex of such a curve, "bird-beaking" where the graft is not apposed to the aortic wall will occur, increasing the risk of graft collapse, migration, and failure of aneurysm exclusion [45-48]. With adequate preoperative planning, landing more proximally and debranching the arch as needed can usually circumvent these issues. To achieve the 20-mm proximal seal required and ensure that the graft will sit in close apposition to the inner curve of the arch, debranching procedures using "hybrid" techniques can be performed, which essentially "move" the branch vessels to a more proximal location, allowing coverage of the origins of these vessels [49-51]. (See 'Arch vessel bypass' below and 'Landing zone classification' above.)

●Distal – The distal seal zone also must be at least 20 mm in length. Typically, the celiac axis is spared given the potential adverse consequences of coverage [52]. However, successful cases of covering the celiac artery to gain an additional 25 mm in seal length have been reported in patients with a documented patent pancreaticoduodenal arcade with a low incidence of mesenteric ischemia [53,54]. The need for the distal end of a thoracoabdominal aneurysm repair to extend below the mesenteric artery necessitates an alternative source of blood flow to the mesenteric and renal arteries before endografting to avoid compromising their flow [51]. (See 'Visceral artery bypass' below.)

Choice of endograft and endograft sizing — Careful preoperative sizing and planning, along with strict adherence to device-specific IFU, leads to the best outcomes. All approved endografts have demonstrated short- and mid-term success in treatment of thoracic aortic aneurysms and have also been used to treat other aortic pathologies. These devices can also be used to treat aortic arch aneurysms following debranching procedures. (See 'Need for debranching procedures' below.)

The larger thoracic aorta necessitates the use of larger-diameter stent-grafts compared with those used for abdominal endovascular repair. Commercially available devices have endograft diameters as small as 21 mm and as large as 46 mm, which allows endovascular repair of native thoracic aortic diameters between 18 and 42 mm. Ten to 20 percent oversizing is recommended for thoracic endografts, although oversizing should be limited to 10 percent for patients with acute and subacute dissection. Excessive oversizing may lead to retrograde aortic dissection, a potentially lethal complication of TEVAR [55,56].

Need for debranching procedures — Placement of the proximal or distal end of the device may require covering important aortic side branches. Debranching procedures involve open surgical vascular bypass to important vessels prior to thoracic stent-grafting placement [51].

Some groups have combined fenestrated or branched abdominal aortic endografts, or other stents in the chimney/snorkel or periscope orientation with thoracic grafts, to avoid the need to perform debranching procedures in the abdomen [57-75]; whether one approach is better than another has yet to be determined [76]. In situ fenestration of the graft (using a needle, laser, or other energy device) has been described, particularly in association with emergency surgery, to avoid the need for left subclavian revascularization [59,77,78]. Single-branch stent grafts are available in the context of feasibility and pivotal trials. Multi-branch stent-grafts are only available via investigational device exemption trials. (See "Endovascular devices for thoracic aortic repair", section on 'Advanced devices'.)

Arch vessel bypass — If the proximal landing zone involves any of the aortic arch vessels, arch vessel bypass (eg, ascending aortic-innominate, ascending aortic-left common carotid, left carotid-subclavian bypass) needs to be considered.

Subclavian revascularization — Observational studies suggest that under most circumstances, preemptive rather than expectant left subclavian artery revascularization does not significantly alter outcomes when coverage of the left subclavian is deemed necessary [79-85]. However, for patients with a dominant left vertebral, hypoplastic right vertebral, or incomplete circle of Willis, planned coverage of the left subclavian should be preceded by left carotid subclavian bypass, as interruption of blood flow in these circumstances has been associated with an increased incidence of stroke and paraplegia [86-91]. Flow to the left subclavian should also be considered in patients with long-length thoracic aortic coverage and for patients with prior abdominal aortic aneurysm repair.

Left subclavian artery (LSA) coverage may be needed to achieve a proximal seal in up to 40 percent of patients treated with thoracic endovascular aortic repair (TEVAR). Whether to routinely revascularize the LSA preoperatively or manage the left extremity expectantly (ie, no preoperative revascularization) remains controversial. A systematic review identified five studies [80-84] in which LSA was performed during 1161 TEVARs, with 444 patients undergoing revascularization [79]. Stroke rates were not significantly reduced for patients undergoing left subclavian revascularization compared with no revascularization (odds ratio [OR] 0.70, 95% CI 0.43-1.14) [79]. There were also no significant differences in rates of spinal cord ischemia with left subclavian revascularization (OR 0.56, 95% CI 0.28-1.10) or death (OR 0.87, 95% CI 0.55-1.39).

Rarely, patients may develop debilitating arm claudication symptoms at a later date, at which time an elective revascularization procedure can be performed. One review reported that only 4 percent of the patients who developed symptoms of upper extremity ischemia required subsequent revascularization [92]. Thus, many advocate selective LSA revascularization. Patients who should be considered for preoperative left subclavian revascularization include those with a patent left inferior mammary artery-coronary bypass, dominant or isolated left vertebral artery, or functioning left upper extremity dialysis arteriovenous access [93]. When coverage of the left subclavian artery is needed, duplex ultrasound of the vertebral and carotid arteries should be performed to determine the optimal procedure to restore left subclavian flow (eg, carotid-subclavian bypass, subclavian-carotid transposition).

When left subclavian revascularization is needed, comparisons of carotid-subclavian bypass and subclavian-carotid transposition have found no significant differences in stroke, spinal cord ischemia, or mortality [83,94].

Carotid revascularization — For proximal landing zones that will cover the left common carotid artery or brachiocephalic trunk, open, antegrade bypass from the ascending aorta or carotid transposition can be performed, or alternatively, extra-anatomic bypass such as carotid-carotid bypass can be performed to avoid sternotomy [95-98].

Visceral artery bypass — Visceral ischemia can occur with coverage of the celiac axis, and in general, we try to avoid celiac coverage. However, some reports have suggested that collateralization through an intact pancreaticoduodenal arcade can allow for extension of the distal seal zone to the level of the superior mesenteric artery (SMA) without physiologic consequence [53]. In a literature review, coverage of the celiac axis during TEVAR for thoracic aortic aneurysm without accompanying celiac artery embolization resulted in only three type II endoleaks (table 1) among 72 patients, and these were successfully treated by coil embolization. Another small study of TEVAR for Type B dissection confirmed the feasibility of this approach.

Stenting to below the SMA or renal artery levels requires revascularization of these vessels via open surgical bypass (debranching), or by using snorkel or chimney stents [99-101], or specialized fenestrated or side-branched grafts [72,73,102,103]. Debranching procedures provide blood flow to the visceral arteries via alternative vessels to allow coverage by the graft of the visceral segment of the aorta [104,105].

Timing of bypass procedure — Debranching procedures are surgical bypasses that reroute blood flow from the aorta to the target vessel.

For visceral debranching, the procedure is performed prior to endovascular repair with inflow typically originating from the iliac arteries. The subsequent endograft repair can be placed at the same setting or delayed for several days or weeks following the original operation, depending on the patient's physiologic status. We generally prefer a staged visceral debranching procedure in advance of thoracic endovascular repair.

Similarly, when subclavian debranching is elected, we typically perform the procedure one to three days prior to the endovascular repair.

MEDICAL RISK ASSESSMENT — Although endovascular repair of the thoracic aorta is associated with lower perioperative morbidity and mortality compared with open surgical repair, there is a risk that conversion to an open repair will be necessary, and thus, patients should be evaluated and prepared as if undergoing an open surgical repair. Whenever possible, patients should undergo a comprehensive assessment of medical comorbidities prior to aortic repair including cardiac, pulmonary, and renal evaluation, also taking into account hypertension and patient age as relevant risk factors for morbidity and mortality. The evaluation of cardiopulmonary risk and risk management strategies are discussed in detail elsewhere. (See "Evaluation of cardiac risk prior to noncardiac surgery" and "Management of cardiac risk for noncardiac surgery" and "Evaluation of perioperative pulmonary risk" and "Strategies to reduce postoperative pulmonary complications in adults".)

PREOPERATIVE PREPARATION

Antibiotic prophylaxis — Antibiotic prophylaxis is recommended within 30 minutes of the skin incision. Appropriate antibiotics are given in the table (table 2) [106]. Antibiotics are discontinued within 24 hours given the lack of added benefit beyond that time frame. (See "Antimicrobial prophylaxis for prevention of surgical site infection in adults", section on 'Vascular surgery'.)

Measures to prevent acute renal injury — The incidence of acute kidney injury following thoracic aortic endografting is 10 to 15 percent [107-110]. Higher incidences of renal dysfunction can occur in patients with type B dissection, as these patients are typically treated only after organ malperfusion has occurred. Important risk factors for postoperative renal dysfunction include poor preoperative renal function, the need for blood transfusion, and the extent of thoracoabdominal aortic disease [110]. (See "Surgical and endovascular management of acute type B aortic dissection".)

Most patients do not experience acute kidney injury as a result of intravenous contrast. Provided that there are adequate seal zones, thoracic endovascular repair can be performed with as little as 60 to 80 mL of contrast. Prevention of contrast-induced nephropathy for those who are at risk is discussed elsewhere. (See "Prevention of contrast-associated acute kidney injury related to angiography".)

Minimizing spinal ischemia — Spinal drainage should be used in cases where there will be extensive coverage of the thoracic aorta, a history of prior open or endovascular aneurysm repair, or presence of internal iliac artery occlusions, all of which are reported to increase the risk for spinal cord ischemia (SCI) with the potential for paraplegia [111-121]. In a review of 72 patients, the incidence of spinal cord ischemia was 12.5 percent for those who had prior abdominal aortic aneurysm (AAA) repair, compared with 1.7 percent for those without (risk ratio 7.2, 95% CI 2.6-19.6) [116]. A retrospective cohort study of endovascular repair (Crawford Type II thoracoabdominal aneurysm) using branched stent-grafts suggested staged repair (median time between stages was five months) reduced the risk for SCI compared with combined procedures (11.1 versus 37.5 percent) [122]. (See 'Spinal perfusion' above.)

Spinal drainage decreases pressure in the subarachnoid space, thereby increasing spinal cord perfusion pressure (spinal cord perfusion pressure = mean arterial pressure - CSF pressure), and is an important adjunct for reducing spinal ischemia following endovascular repair of the thoracic aorta [123,124]. Spinal drainage is accomplished by placing a drain at the level of the L3-L4 disc into the subarachnoid space. Neuromonitoring for spinal ischemia during the procedure and in the postoperative period is discussed separately. (See "Anesthesia for endovascular aortic repair", section on 'Neuromonitoring for spinal cord ischemia'.)

ENDOGRAFT PLACEMENT — Endovascular repair of the thoracic aorta is typically performed under general endotracheal anesthesia. Technical success rates are generally high. In one study, technical success was achieved in 87 percent of patients with aortic aneurysm and 89 percent of patients with aortic dissection [125].

Vascular access — Performance of the procedure requires the delivery of a large-bore sheath into the aorta as well as a separate access for arteriography. These are typically accomplished using femoral cut down. There are no thoracic endovascular devices labelled for percutaneous use [126]. However, with the growing appeal of percutaneous repair of the abdominal aorta, it is likely over time that the application of this technique for thoracic endovascular repair will follow suit [127].

Anticipation of the need for other access techniques, which is required in 9.4 to 23.8 percent of patients, is important because of the obligatory large sheath size for delivery of the device [5,10,128]. Passage of the sheath through a small-diameter, tortuous, or excessively calcified external iliac artery can lead to iliac artery disruption. Adjunctive and alternative access techniques include balloon angioplasty/stenting of the iliac arteries prior to sheath placement, creation of an iliac conduit, direct exposure of the common iliac artery, direct delivery through the abdominal aorta, or use of a controlled rupture technique with a specialized device (eg, Solopath sheath, Terumo).

Antegrade access to place a descending thoracic endograft can also be obtained using a graft anastomosed to the ascending aorta [126,129], typically as a means to address the residual dissection flap after repair of type A aortic dissection. (See "Surgical and endovascular management of acute type A aortic dissection".)

Graft deployment — Once access is achieved, aortography or other techniques such as intravascular ultrasound or transesophageal echocardiography [130,131], are used together to position and deploy the endograft precisely at the target locations [132]. When deploying a graft near the aortic arch, it is important to provide a projection that adequately splays out the arch vessels. A 30- to 60-degree left anterior oblique projection is generally used. For a distal landing zone near the celiac artery, a lateral projection is required. The instructions for use (IFUs) provide the precise sequence of steps for individual devices.

Prior to graft deployment, we generally lower the blood pressure keeping the mean blood pressure in the 60s, which helps prevent the graft from prematurely deploying and moving distally due to pressure (ie, the "wind-sock effect"). Once the device is deployed, the stent-graft is typically ballooned at the proximal and distal landing zones, as well as at graft junctions. Lowering the pressure may also be useful during graft ballooning.

Evaluating for endoleak — Repeat aortography is performed at the conclusion of the procedure to ensure effective sac exclusion, preservation of essential vessels, and to detect any evidence of endoleak. An endoleak is the persistent flow in the aneurysm sac following endovascular repair of the aorta. The classification (table 1) and management of endoleak are discussed in detail separately. (See "Endoleak following endovascular aortic repair", section on 'Etiology and classification'.)

Once exclusion of the sac has been confirmed, the device sheath is removed, and the arteriotomy is repaired or closed with a closure device.

POSTOPERATIVE CARE AND FOLLOW-UP — Postoperatively, the patient is transferred to a monitored setting for routine neurologic and vascular checks to detect for complications such as stroke, spinal cord ischemia, or extremity ischemia. (See 'Perioperative morbidity and mortality' below.)

In the absence of complications, recovery is generally rapid and patients require only two to three days on a regular floor prior to discharge.

Postoperative endograft surveillance — Computed tomographic (CT) angiography is usually obtained within a month of the procedure, followed by an imaging study at six months and annually thereafter. Thoracic endovascular aortic repair (TEVAR) in patients with less than ideal anatomy warrants more rigorous follow-up [133]. Noncontrast CT allows for measurement of the sac diameter and is sufficient in most circumstances to document effective aneurysm exclusion. Magnetic resonance angiography is an alternative, although it is of limited applicability in patients with significant renal dysfunction.

Secondary aortic intervention is relatively common following thoracic endovascular aortic repair [134,135]. Evidence of attachment site endoleak is intervened upon promptly. Type II endoleaks can be observed if the sac does not enlarge. (See 'Late complications and outcomes' below and "Endoleak following endovascular aortic repair", section on 'Endoleak management after TEVAR'.)

PERIOPERATIVE MORBIDITY AND MORTALITY — Perioperative mortality with second-generation thoracic stent-grafts placed under elective circumstances is low, ranging from 1.9 to 3.1 percent [5,6,8]. The operative indication for thoracic endovascular aortic repair (TEVAR) was not found to be a predictor of poor patient outcome in a review of the National Surgical Quality Improvement Program (NSQIP) database [136], or in a later single-institution review [137]. However, patients undergoing thoracic aortic endografting for emergency reasons, such as due to aortic rupture or aortic dissection, have higher rates of perioperative (30-day) mortality (23 versus 6.2 percent in NSQIP study) [125,136,138-142]. Late mortality following emergency repair was significantly worse in one review [143], but in another review no different among those who survived >30 days [139]. In the NSQIP review, increasing surgical complexity significantly increased mortality and serious adverse event rates. In a study that combined perioperative morbid events (myocardial infarction, respiratory events such as pneumonia or ventilation for more than 24 hours, stroke, and paraplegia), the overall incidence of perioperative morbidity was 9 percent [5]. The risk of perioperative death is associated with the degree of chronic renal dysfunction [144-146]. No differences in survival have been identified for male versus female patients undergoing TEVAR [139,147-152].

Complications specific to graft placement are related to the access site and ischemia related to thromboembolism during graft placement, the consequences of covering aortic side branches, or more rarely, retrograde aortic dissection, which can occur during the initial placement or can be delayed [150-154]. In a systematic review, the pooled incidence of retrograde aortic dissection was 2.5 percent and was associated with hypertension, history of vascular surgery, acute (versus chronic) aortic dissection, aortic dissection (versus aneurysm), and use of bare (versus covered) stents [154].

Aortobronchial or aortopulmonary fistulas, typically related to bronchial compression as a consequence of endoleak, are rare complications. In one review, these were lethal in 33 and 45 percent of patients, respectively [155].

Iliofemoral access complications are similar to those that occur with endovascular repair of the abdominal aorta. In one review of iliofemoral complications associated with thoracic endovascular repair, the complication rate was 12 percent [128]. (See "Complications of endovascular abdominal aortic repair", section on 'Access site complications'.)

Ischemic complications

Spinal cord ischemia — The risk of spinal cord ischemia (SCI) has been reported to be between 3 to 11 percent [111,118,125,138,145,146,156-162], comparable to the rate of open surgery [163]. (See "Overview of open surgical repair of the thoracic aorta".)

Some studies have demonstrated lower rates of SCI with TEVAR than with open surgery [8,13]. In a well-performed, retrospective review of 724 patients at a single institution who were treated with either TEVAR (n = 352) or open surgery (OS; n = 372) for thoracic or thoracoabdominal aneurysms, no statistically significant difference in the rate of SCI was found between the two approaches (4.3 versus 7.5 percent, respectively) [13]. In a retrospective review of 424 patients who underwent TEVAR, of the 12 patients developed spinal cord ischemia, one-half had a prior open or endovascular aortic repair [161]. The onset of spinal cord ischemia developed at a mean of 10.6 hours following repair. In this manner, only a portion of the aorta is covered at a time.

Studies using protocols calling for proactive spinal cord protection report a similar range of rates of spinal cord ischemia: 1.1 percent in one review and 6 percent in another [118,164]. In a systematic review, pooled rates for spinal cord ischemia for series reporting routine prophylactic drain placement or no prophylactic drain placement were 3.2 and 3.5 percent, respectively.

The extent of thoracic aortic coverage is the greatest risk factor for spinal cord ischemia [13,157]. Other studies have identified perioperative hypotension and long procedure duration [117,118,165,166], and visceral artery reimplantation as risk factors [157]; another review identified renal insufficiency as significant [161].

Cerebrovascular ischemia — Because the proximal seal zone is in proximity to the carotid and vertebral arteries, embolic strokes can occur following TEVAR. Reported risk factors for embolic stroke include the need for proximal deployment of the graft, presence of mobile atheromata in the arch, and prior stroke [167-170]. Emboli through the vertebral arteries arising from the subclavian may be the source of posterior circulation strokes [87,91,171]. Perioperative stroke has ranged from 4 to 8 percent [80,138,172-177], comparable to open surgery [163].

Silent cerebral embolization occurs frequently, but the significance is not known for certain [178].

Extremity ischemia — As described above, planned coverage of the left subclavian artery in patients at risk should be preceded by carotid-subclavian bypass or transposition. (See 'Arch vessel bypass' above.)

Left upper extremity ischemia is infrequent after coverage of the left subclavian artery. Symptoms can occur to a variable extent but require intervention in a minority of patients [81,179-181]. (See 'Arch vessel bypass' above.)

In a systematic review that included 4906 patients, it was noted that although revascularization decreased the incidence of later ischemic complications, perioperative mortality and other complications were increased [86]. In a review of 111 patients undergoing TEVAR without prior extremity bypass, 13/50 patients in the full-coverage group and 2/25 patients in the partial-coverage group suffered from vertebrobasilar insufficiency [180]. No paraplegia or stroke was observed.

Visceral ischemia — Visceral ischemia can occur with coverage of the celiac axis, although reports have suggested that collateralization through an intact pancreaticoduodenal arcade allows for extension of the distal seal zone to the level of the superior mesenteric artery (SMA) without physiologic consequence [53,182]. Similarly, stenting to below the level of the SMA or renal artery requires revascularization of these vessels, or the use of specialized grafts [103]. (See 'Visceral artery bypass' above and 'Need for debranching procedures' above.)

In a review of 171 patients, independent predictors of acute kidney injury (AKI), which occurred in 24 patients (14 percent), included preoperative depressed estimate glomerular filtration rate, extent of thoracoabdominal repair, and postoperative transfusion [110]. Survival was significantly lower for those who experienced AKI.

Postimplantation syndrome — Postimplantation syndrome can occur during the early postoperative period and is characterized by leukocytosis, fever, and elevation of inflammatory mediators such as C-reactive protein, IL-6, and TNF-alpha [183-185]. It is thought to be due to endothelial activation by the endoprosthesis. For thoracic aortic stent-grafts, development of either unilateral or bilateral reactive pleural effusions is not uncommon, with a reported incidence of 37 percent to 73 percent [184,186,187].

LATE COMPLICATIONS AND OUTCOMES — Late outcomes for thoracic aortic stent-grafting are primarily related to the natural history of the disease being treated, as well as the consequences of device complications such as endoleak, device migration, infolding, or collapse [47].

A retrospective review of the United States Medicare database identified nearly 12,000 patients who underwent endovascular repair of the thoracic aorta between 2005 and 2010 for a variety of indications [142]. Median survival was 57.6 months (95% CI 55 to 61 months). Early and late mortality depended upon underlying aortic pathology. Patients undergoing thoracic endovascular aortic repair (TEVAR) for acute dissection or traumatic transection had the highest incidence of perioperative death but also had the lowest incidence of late mortality, perhaps due to younger age and smaller number of comorbidities. Isolated aneurysm patients, in particular those not requiring subclavian artery coverage, had the lowest incidence of perioperative death, although they had a relatively higher incidence of late death. Aortic rupture was associated with a high incidence of early and late death. A sobering finding of this large analysis was that among patients who survived to 180 days, 6 to 12 percent of patients died per year, depending on aortic diagnosis. The authors of the study questioned whether endovascular repair for patients with chronic disease, who have an annualized death rate of >10 percent/year, is appropriate.

The incidence of endoleak following thoracic aortic stent placement is lower than for endovascular repair of the abdominal aorta and is estimated at 3.9 to 15.3 percent [5,6,8,188]. The incidence of endoleak at five-year follow-up with the Gore TAG device was 4.3 percent in one review. Type I attachment site leaks are the most common type in these and other studies. In a review of 344 patients undergoing TEVAR, type II endoleaks were more common and occurred most commonly at the left subclavian artery and intercostal branch sites, followed by visceral vessels [189]. Among patients who suffered from secondary-endoleak-related rupture, few (2/10) were related to type II endoleak. Ongoing surveillance for endoleak is necessary [6,190]. (See 'Postoperative endograft surveillance' above and "Endoleak following endovascular aortic repair", section on 'Endoleak management after TEVAR'.)

Migration of the graft (>10 mm) caudally can occur, with a published incidence of 1 to 2.8 percent over a 6- to 12-month period [5,6,8]. Factors predisposing to migration include excessive oversizing and tortuous seal zone anatomy. Device infolding or collapse can also occur, primarily in young trauma patients, and is related to severe proximal aortic angulation or excessive oversizing of the device at the time of placement [45,191]. These patients present with symptoms of acute aortic occlusion [192]. In the case of multiple overlapping stents, device separation has also been reported [193]. Many of these issues can be managed using endovascular techniques. (See 'Choice of endograft and endograft sizing' above.)

The rate of secondary intervention required following stent-grafting due to either endoleak or device migration is 3.6 to 24 percent and depends on the duration of follow-up [5,6,134,194]. In a review of 585 patients, 12 percent needed reintervention at a median follow-up of 5.6 months [134]. The need for intervention differed depending upon the indication for initial intervention at 21.3 percent for acute dissection, 16.7 percent for chronic dissection, 10.8 percent for degenerative aneurysm, 8.1 percent for traumatic transection, and 1.5 percent for penetrating ulcer. For degenerative aneurysms, reintervention was needed primarily to treat type I and type III endoleaks. Repairs that use advanced devices and techniques may have even higher rates of reintervention [74].

The largest published series, which has reported one-year follow-up, included 443 patients treated with endovascular stents for a variety of indications, both emergency and elective: thoracic aortic aneurysm (249 patients), thoracic aortic dissection (131 patients), traumatic aortic injury (50 patients), and false anastomotic aneurysm (13 patients) [125]. One-year all-cause mortality among patients treated for aortic aneurysm and aortic dissection were 20 and 10 percent, respectively. These results should not be compared directly to historical outcomes following surgical repair. Patients included in this series had a greater burden of comorbid disease, and many would not have been candidates for surgery. The short duration of follow-up precludes direct comparison with the durable effects of successful surgical repair.

The largest of the early series, for which there is medium-term follow-up, was a prospective, uncontrolled study of a first-generation, custom-fabricated self-expanding stent-graft, including 103 patients with descending thoracic aortic aneurysms, 60 percent of whom were not candidates for conventional surgery [177].

After a 1.8-year follow-up, the following findings were noted:

●Fatal complications occurred in 4 percent, including rupture of the treated aneurysm, stent-graft erosion into the esophagus (aortoesophageal fistula), arterial injury, and excessive bleeding.

●Late stent-graft complications occurred in 38 percent of patients and included stent-graft malpositions or removal, endoleak, aortic dissection, distal embolization, gut ischemia, and infection.

●In a subsequent report at 4.5 years of follow-up, actuarial survival at one, five, and eight years was 82, 49, and 27 percent, respectively [175]. Patients who had been identified as suitable surgical candidates at the time of stent-graft placement had significantly better survival at one year (93 versus 74 percent) and five years (78 versus 31 percent).

In a study of thoracic stenting in the emergency setting, four deaths occurred at a mean follow-up of 36 months, three of which were attributed to late procedural complications (one aneurysm, one dissection, and one traumatic transection) [141]. Reintervention rates were similar between the open surgical and endovascular repair groups.

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Aortic and other peripheral aneurysms".)

INFORMATION FOR PATIENTS — UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5^th to 6^th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10^th to 12^th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.

Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.)

●Basics topics (see "Patient education: Thoracic aortic aneurysm (The Basics)")

SUMMARY AND RECOMMENDATIONS

●Repair of thoracic aorta may be indicated for various pathologies of the thoracic aorta. For patients with or without involvement of the abdominal aorta, endovascular stent-grafting has gained acceptance as a reasonable alternative to open surgery. Despite the significant rate of secondary intervention required following stent-grafting, the decreased perioperative morbidity of this approach makes it preferable to open repair for many indications. (See 'Indications for endovascular aortic repair' above.)

●The preprocedural evaluation of patients undergoing thoracic endovascular repair requires medical risk assessment and a careful quantitative and qualitative evaluation of aortic arch and aortoiliac anatomy to determine suitability for endovascular repair. (See 'Medical risk assessment' above and 'Planning TEVAR' above.)

●Available thoracic endovascular grafts have three components (delivery system, main body, and extensions). The endovascular graft is constructed by the sequential delivery and deployment of device components in vivo. Although variations exist from device to device, there are no clear advantages of one device over another. All approved endografts have demonstrated short- and mid-term success in treatment of thoracic aortic aneurysms. (See 'Thoracic endografts' above and "Endovascular devices for thoracic aortic repair".)

●Routine follow-up imaging is mandatory following thoracic endovascular stent-grafting to evaluate endograft integrity and positioning. We use computed tomography to assess the graft at initial postoperative follow-up, then 6 and 12 months postoperatively, and annually thereafter. (See 'Postoperative endograft surveillance' above.)

●Perioperative mortality with second-generation thoracic stent-grafts placed under elective circumstances is low (<3 percent). Perioperative mortality in patients undergoing thoracic aortic endografting for emergency reasons, such as due to aortic rupture or aortic dissection, is higher. Perioperative complications specific to graft placement are related to the access site used to introduce the device, ischemia related to thromboembolism during graft placement, or as a consequence of covering aortic side branches. The risk of spinal cord ischemia is comparable to open surgery with rates between 3 and 11 percent. (See 'Perioperative morbidity and mortality' above.)

●Secondary reintervention is not uncommon following thoracic endografting and is related to endoleak, graft migration, and progression of the underlying disease that indicated the endograft. Continued surveillance is essential to prevent late aortic events. (See 'Late complications and outcomes' above.)

ACKNOWLEDGMENTS — The UpToDate editorial staff acknowledges Emile R Mohler, III, MD (deceased), who contributed to an earlier version of this topic review.

The UpToDate editorial staff also acknowledges Ronald M Fairman, MD, who contributed to an earlier version of this topic review.