Thoracic Aortic Aneurysm and TEVAR

23.1Definition and presentation

A descending thoracic aortic aneurysm is a focal dilatation of the descending aorta. The principal risk is rupture or dissection, which rises steeply when the diameter exceeds 6.0 cm. Below 5.5 cm, the annual event rate in a standard-risk patient is typically lower than the periprocedural risk of intervention.

Most aneurysms are asymptomatic. Symptomatic disease behaves as an impending complication rather than stable disease and is an indication for repair regardless of absolute diameter. Symptomatic presenting features include:

• Back pain mapping to the aneurysm.
• New hoarseness.
• Embolic events.

23.2Repair threshold and treatment decision

The elective repair threshold for a standard-risk patient is 5.5 to 6.0 cm (ACC/AHA 2022 and ESVS 2017; the earlier ESC 2014 guidance used 6.0 cm) ACC/AHA 2022 · ESVS 2017 · ESC 2014. This threshold is downshifted for patients with genetic aortopathies (Marfan, Loeys-Dietz, and vascular Ehlers-Danlos syndromes), rapid growth on serial imaging, saccular morphology, or a family history of dissection. Rapid expansion means growth of at least 0.5 cm per year, and that rate alone justifies repair below the absolute diameter threshold. For genetic aortopathies, the specific syndrome and family history determine the applicable threshold rather than a single universal diameter. Baseline medical management applies to all patients regardless of the repair decision: impulse and blood-pressure control (beta-blockade or an equivalent agent to reduce aortic wall stress, with an ARB or ACE inhibitor layered to target), a statin, and smoking cessation.

The treatment decision follows a stepwise logic:

1. Decide surveillance versus repair: Below threshold, surveillance is maintained. Confirmed enlargement, threshold criteria, or symptoms transition the patient to intervention planning. A deliberate no-intervention pathway is established for patients with prohibitive operative risk or limited life expectancy.
2. Decide endovascular versus open repair: Thoracic endovascular aortic repair (TEVAR) is favored for older patients, suitable endovascular anatomy, and those lacking physiological reserve for a thoracotomy. Open repair is reserved for younger fit patients, hostile anatomy, connective-tissue disease where a seal in a fragile aorta lacks durability, proximal arch involvement that exceeds branched-device capability at the local center, and chronic dissection necessitating eventual thoracoabdominal replacement.
3. Plan access strategy: Access logistics are finalized prior to the procedure. Older patients and women frequently require femoral cut-down, an iliac conduit, or percutaneous closure with a large-bore device.
4. Adjust for emergency: Symptomatic disease permits a short delay for evaluation, whereas overt rupture or contained leak demands immediate intervention outside the elective framework.

In the Gore TAG pivotal trial and a 2014 meta-analysis, TEVAR gave lower 30-day mortality and shorter hospital stays than open repair, with broadly comparable mid-term aneurysm-related survival Cheng 2010 · TAG Investigators 2008. Long-term outcomes for TEVAR are dominated by seal-zone integrity and reintervention for endoleak or device migration. A durable seal needs at least 2 cm of adequately sized, non-aneurysmal, non-dissected aorta in both the proximal and distal landing zones; inadequate seal-zone length is a primary driver of type I endoleak ESVS 2017. High-volume aortic centers demonstrate better risk-adjusted outcomes for both modalities.

23.3Left subclavian artery coverage and revascularization

Most thoracic stent grafts achieving a durable proximal seal in the standard descending aorta landing zone require coverage of the left subclavian artery origin. Revascularization (carotid-subclavian bypass or left subclavian-to-common-carotid transposition) is recommended before or concurrent with TEVAR when specific anatomical or physiological risk features are present ACC/AHA 2022 · ESVS 2017.

Carotid-subclavian bypass using a small-diameter prosthetic graft is the most common technique, and it is well tolerated under local or regional anesthesia in the fragile patient; the proximal subclavian stump is ligated or coil-occluded to prevent type II endoleak. Transposition avoids a prosthetic graft and offers a native-to-native anastomosis profile. Emergent settings often force coverage without prior revascularization, accepting the deferred stroke and left arm claudication risks until stabilization is achieved.

23.4Spinal cord protection and complications

Spinal cord ischemia is a major complication of extensive TEVAR. The primary mechanism is collateral collapse. The cord can infarct not only during the procedure but hours to days afterward, which is why drain retention, blood-pressure targets, and serial neurological checks continue through the first 24 to 48 hours. Risk increases with the length of aortic coverage, prior abdominal or descending repair that disrupted collaterals, low intraoperative blood pressure, and limited collateral reserve (severe pelvic atherosclerosis, prior hypogastric occlusion, or prior un-revascularized left subclavian coverage).

High-volume centers use a layered protection bundle to mitigate ischemia risk ESVS 2017 · Estrera 2005. Key interventions include:

• Cerebrospinal fluid drainage to lower spinal canal pressure and widen the perfusion gradient.
• Permissive hypertension to preserve collateral perfusion.
• Staged repair to allow collateral network expansion.
• Prompt neurological assessment for immediate escalation of oxygen delivery and perfusion targets.

Numeric targets anchor the bundle: keep cerebrospinal fluid pressure at or below 10 mmHg on the lumbar drain, and support mean arterial pressure at 80 to 90 mmHg during and for the first 24 to 48 hours after extensive coverage to hold the collateral perfusion gradient ESVS 2017 · Estrera 2005.

Retrograde type A dissection is a rare but high-mortality complication occurring when an intimal tear in the ascending aorta propagates retrograde from the stent edge. Risk factors include proximal arch landing (zone 0 and 1), aggressive proximal oversizing, post-deployment ballooning over a fragile arch, and underlying genetic aortopathy or chronic dissection ESVS 2017 · Chen 2017 · Coselli 2016 · Lee 2015 · Canaud 2014. Avoidance strategies mandate conservative device oversizing at the lower end of the manufacturer-recommended range, elimination of unnecessary proximal ballooning, and a lower threshold for open repair when zone 0 or 1 landing is required in a fragile aorta.

23.5Post-TEVAR imaging surveillance

Surveillance after TEVAR follows a structured cadence to detect endoleak, assess sac size, and verify device position. Acceptance of lifelong imaging and possible reintervention is an inherent part of the TEVAR pathway. Loss to follow-up is the single most common preventable cause of late TEVAR failure, so the surveillance plan (next study date, imaging site, and responsible team) is agreed and documented before discharge.

If the graft is stable with a shrinking or unchanged sac at 12 months, imaging intervals are often extended based on center protocol; absolute intervals for extended surveillance beyond 12 months are not uniformly established. Conversely, an unstable seal, type Ia endoleak, or distal sac growth shortens the surveillance interval and triggers evaluation for reintervention.

23.6Areas of controversy

Several aspects of descending thoracic aortic aneurysm management remain unsettled:

• Spinal drain utilization: The choice between routine versus selective cerebrospinal fluid drainage remains a center-level protocol decision rather than a universal standard, balancing ischemia protection against bleeding and catheter-related risks ESVS 2017.
• Subclavian revascularization staging: Whether left subclavian revascularization is performed as a staged prior operation or concurrently on the day of TEVAR varies by center logistics and patient physiological reserve ESVS 2017.
• Branched endografting: Emerging branched and fenestrated thoracic devices that preserve subclavian flow without extra-anatomic bypass represent an active area of practice shift at specialized centers, potentially altering standard coverage algorithms in the future.