Residency · Residency · Interventional Radiology

Thoracic Endovascular Aortic Repair (TEVAR) Basics

Indications

Descending Thoracic Aortic Aneurysm (DTAA)

The repair threshold for descending thoracic aortic aneurysms is 5.5-6.0 cm in diameter, with a lower threshold applied for patients with connective tissue disorders such as Marfan syndrome. TEVAR has become the first-line treatment for descending thoracic aneurysms in patients with suitable anatomy, while open repair is reserved for those with connective tissue disorders, young patients, or anatomy unsuitable for endovascular repair.

Acute Type B Aortic Dissection

Uncomplicated type B dissection is managed medically with blood pressure control, heart rate control, and pain management. Complicated dissection, defined by malperfusion, rupture, rapid expansion, or refractory pain and hypertension, requires TEVAR as the treatment of choice. The principle is to cover the primary entry tear, thereby redirecting flow into the true lumen. The INSTEAD trial demonstrated that TEVAR improved aortic remodeling and long-term outcomes compared with medical therapy even in uncomplicated type B dissection, though routine application to all uncomplicated cases remains controversial. The ADSORB trial similarly showed that TEVAR promoted favorable remodeling in acute uncomplicated type B dissection.

Chronic Type B Aortic Dissection

Aneurysmal degeneration of the false lumen to greater than 5.5-6.0 cm is an indication for repair. Treatment is more challenging than in acute dissection because the dissection flap has thickened and chronic remodeling has occurred.

Traumatic Aortic Injury (Blunt Aortic Injury)

The most common site of injury is the aortic isthmus, just distal to the left subclavian artery origin at the ligamentum arteriosum. TEVAR has replaced open repair as the current standard of care. Timing is ideally delayed beyond 24 hours in hemodynamically stable patients to allow medical optimization, with immediate repair reserved for unstable patients. The minimal aortic disease present in young trauma patients allows excellent seal, and oversizing should be conservative (less than 10%) in young patients to prevent late aortic remodeling complications.

Other Indications

Additional indications include penetrating aortic ulcer, intramural hematoma with progression, aortic pseudoaneurysm, mycotic aneurysm as a bridge to definitive treatment, and select cases of aortic coarctation.

Landing Zone Planning

Ishimaru Classification of Aortic Zones

Zone 0 encompasses the ascending aorta proximal to the innominate artery and requires arch debranching or total arch replacement. Zone 1 lies between the innominate and left common carotid artery and requires carotid-carotid bypass or chimney/branched grafts. Zone 2 spans from the left common carotid to the left subclavian artery and may require left subclavian revascularization. Zone 3, the standard TEVAR landing zone, begins just distal to the left subclavian artery. Zone 4 encompasses the mid-descending thoracic aorta. Both the proximal and distal seal zones should be at least 20 mm in length.

Left Subclavian Artery Coverage

Coverage of the left subclavian artery is often necessary to achieve adequate proximal seal when landing in zone 2. Revascularization is recommended when there is a patent left internal mammary artery graft to the LAD, a dominant left vertebral artery, left arm dialysis access, prior infrarenal aortic repair (where spinal cord perfusion depends on subclavian collateral), or planned extensive aortic coverage that increases spinal cord ischemia risk. Revascularization options include surgical carotid-subclavian bypass or transposition, or endovascular chimney/snorkel stent-grafts. SVS guidelines recommend routine revascularization in elective cases.

Spinal Cord Ischemia (SCI)

Risk Factors

The risk of spinal cord ischemia increases with coverage of long aortic segments (greater than 20 cm), prior or concomitant infrarenal aortic repair that eliminates hypogastric-to-spinal collaterals, left subclavian artery coverage without revascularization, hypotension during or after the procedure, and renal failure.

Artery of Adamkiewicz

This major segmental feeder to the anterior spinal artery typically arises from T8-L2, usually from the left side between T9-T12. Coverage of its origin is the theoretical mechanism of spinal cord ischemia after TEVAR. CTA or MRA can identify this vessel in some patients.

Prevention Strategies

Prophylactic strategies include lumbar CSF drainage maintaining CSF pressure below 10 mmHg with drainage of up to 15 mL per hour, maintenance of mean arterial pressure above 80-90 mmHg to augment spinal cord perfusion pressure, staging of extensive repairs when possible, revascularization of the left subclavian artery when covered, and avoidance of perioperative hypotension.

SCI Management

When spinal cord ischemia occurs, immediate CSF drainage should be placed if not already present, aggressive blood pressure augmentation targeting a MAP above 90 mmHg should be initiated, and dexamethasone may be considered though its benefit is controversial. Immediate recognition and treatment are critical because delayed treatment leads to permanent paraplegia.

TEVAR Technique

Access

Bilateral femoral access is obtained, with one side used for the device and the other for an imaging catheter. Large sheaths of 20-25 French are required, necessitating careful assessment of iliofemoral access vessels on CTA. An iliac conduit, a surgically created conduit from the common iliac artery, is used when the iliofemoral vessels are too small or diseased. Transapical access is emerging for select cases.

Deployment

The device is positioned with its proximal edge at the planned landing zone. Controlled hypotension or rapid ventricular pacing is induced to reduce aortic pulsatility during deployment, preventing windsocking (distal migration of the graft during deployment). The graft is deployed and the proximal and distal seal zones are balloon-molded. Completion angiography assesses seal, branch vessel patency, and endoleak.

Key Technical Points

Oversizing should be 10-20% larger than the native aortic diameter, with less oversizing in dissection (5-10%) to avoid pressurizing the false lumen through new intimal tears. A minimum of 2 cm overlap between components is needed in modular systems, and complete coverage of the diseased segment with landing in healthy aorta should be planned.

Complications

Endoleak follows the same classification as EVAR, with type I being the most clinically significant. Stroke occurs in 2-5% of cases, primarily with zone 0-2 landing, and relates to arch manipulation and wire/catheter passage. Spinal cord ischemia has an incidence of 3-8% and is higher with extensive coverage. Left subclavian steal can cause arm claudication and vertebrobasilar insufficiency. Retrograde type A dissection is rare (1-2%) but catastrophic, requiring emergent open repair. Access vessel injury including iliac rupture and dissection occurs especially in small or calcified vessels. Bird-beak deformity, an incomplete apposition of the graft to the inner curve of the arch, may lead to type Ia endoleak.

Key Trials

The INSTEAD trial compared TEVAR plus medical therapy against medical therapy alone for uncomplicated type B dissection. The extended follow-up (INSTEAD-XL) showed TEVAR improved aortic remodeling at 5 years but conferred no mortality benefit in uncomplicated cases. The ADSORB trial demonstrated that TEVAR promoted false lumen thrombosis and aortic remodeling in acute uncomplicated type B dissection at one year. Multiple registry studies have confirmed that TEVAR carries lower perioperative mortality (2-5%) compared with open repair (10-20%) for descending thoracic aneurysms.

<image>Illustration of the Ishimaru aortic landing zones for TEVAR. An anterior view of the aortic arch and descending aorta with zones 0-4 labeled and color-coded. Zone 0 spans the ascending aorta proximal to the innominate artery; Zone 1 is between the innominate and left common carotid arteries; Zone 2 is between the left common carotid and left subclavian arteries; Zone 3 begins just distal to the left subclavian; Zone 4 encompasses the mid-descending aorta. The supra-aortic branch vessels are labeled. An annotation indicates the minimum 20 mm seal zone requirement and lists considerations for each zone (debranching needs, subclavian coverage implications).</image>

<image>Diagram of TEVAR for complicated acute type B aortic dissection. Three panels: (1) Pre-procedure CTA showing the primary entry tear just distal to the left subclavian artery with a true lumen (compressed) and false lumen (expanded), and malperfusion of the left renal artery arising from the true lumen; (2) TEVAR graft deployed covering the primary entry tear with the proximal edge in Zone 3, redirecting flow into the true lumen; (3) Post-TEVAR result showing true lumen expansion, false lumen thrombosis in the covered segment, and restored renal perfusion. Cross-sectional insets at the level of the renal arteries show true/false lumen configuration before and after treatment.</image>

<image>Illustration of spinal cord blood supply and the risk of spinal cord ischemia during TEVAR. A lateral view of the thoracolumbar spine showing the anterior spinal artery fed by segmental arteries, with the artery of Adamkiewicz highlighted at T9-T12. A TEVAR graft is shown covering a long segment of the descending aorta, with the covered segmental arteries highlighted in red. Collateral pathways (from the subclavian artery via the vertebral artery, and from the hypogastric arteries) are shown in blue. A text box lists risk factors for SCI and prevention strategies including CSF drainage and MAP targets.</image>

Clinical Pearls

TEVAR has transformed the management of descending thoracic aortic pathology and has largely replaced open repair for most anatomically suitable patients. Left subclavian artery coverage is common, and the operator must always assess whether revascularization is needed by checking for a LIMA graft, dominant vertebral artery, or dialysis access. Spinal cord ischemia is the most feared complication, and prophylactic CSF drainage with MAP augmentation is essential for high-risk cases. In traumatic aortic injury, TEVAR is now the standard of care, with conservative oversizing (less than 10%) in young patients helping prevent late complications. In type B dissection, the goal is to cover the primary entry tear and promote true lumen reexpansion while avoiding excessive oversizing that could create new intimal tears. Retrograde type A dissection after TEVAR is rare but fatal if not recognized immediately, making postoperative monitoring essential.

References

• Nienaber CA et al. Randomized comparison of strategies for type B aortic dissection: the INSTEAD-XL trial. Circulation 2013
• Brunkwall J et al. Acute dissection type B: the ADSORB trial. J Vasc Surg 2014
• Defined by the SVS/STS Clinical Practice Guidelines on Thoracic Aortic Disease. J Vasc Surg 2022
• Defined by the ESVS Clinical Practice Guidelines on Descending Thoracic Aorta Diseases 2024
• Defined by the Society of Thoracic Surgeons Expert Consensus on TEVAR for Traumatic Aortic Injury

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