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Thoracic aortic aneurysm

Summary

Thoracic aortic aneurysm (TAA) is the focal dilatation of the thoracic aorta to more than 1.5 times its normal diameter. TAAs are classified by location as affecting the ascending aorta, descending aorta, or aortic arch. Men of advanced age are at a higher risk of forming TAAs; other risk factors include trauma, connective tissue disorders, and hypertension. TAAs are frequently asymptomatic and therefore detected incidentally. If symptomatic, they may manifest with a feeling of pressure in the chest, thoracic back pain, and signs of mediastinal obstruction (e.g., difficulty swallowing). The initial test is often a chest x-ray, which may show a prominent aortic arch. CT with contrast is used to confirm the diagnosis and determine the extent of the aneurysm. Observation, close follow-up, and reduction of cardiovascular risk factors are indicated for small aneurysms whereas pronounced or rapidly expanding aneurysms require surgery. TAA rupture and dissection are life-threatening conditions that require emergency surgical repair to prevent cardiac tamponade, hemothorax, and death.

Definition

Epidemiology

References:[2][3]

Epidemiological data refers to the US, unless otherwise specified.

Etiology

References:[6][7]

Classification

References:[8][9]

Pathophysiology

References:[8][2][10]

Clinical features

Aortic aneurysms are mostly asymptomatic or have nonspecific symptoms. They are often disovered incidentally on imaging.

References:[8][11][12]

Diagnostics

Imaging [13][14][15][16]

Chest x-ray

CT angiography chest

  • Indications: best confirmatory test for TAAs
    • Abnormal findings on chest x-ray, ultrasound, or echocardiography
    • Interventional planning and follow-up
    • Detailed evaluation of the extent, length, angulation, and diameter of the aneurysm
    • Evaluation of aortic branch involvement
  • Supportive findings [14][15]
    • Dilatation of the aorta [13]
    • Possible mural thrombus (nonenhancing)
    • Possible dissection, perforation, or rupture

Additional imaging

  • MR angiography chest with and without IV contrast
    • Indication: Consider as an alternative to CTA. [15]
    • Supportive findings: similar to CTA
    • Disadvantages
      • Prolonged duration
      • Less accurate than CTA in allowing for the visualization of branch vessel involvement [15]
  • Transthoracic echocardiography [15]
    • Indications
      • Rapid assessment in hemodynamically unstable patients
      • Evaluation for concomitant heart disease
    • Supportive findings
  • Transesophageal echocardiography: allows for more accurate assessment than TTE [15]
    • Indication: intraoperative monitoring
    • Disadvantages
      • Less accurate than CTA in allowing for the visualization of branch vessel involvement
      • Limited visualization of pathologies above the gastroesophageal junction
  • Catheter angiography (aortography) [16]
    • Indications
      • Evaluation and possibly treatment of coexisting coronary artery disease
      • Assessment of aortic lumen and branch vessels
    • Supportive findings: contrast column in the lumen of the aneurysm
    • Disadvantages
      • May mask the actual diameter of the aneurysm [14]
      • Thrombus-filled discrete aneurysms might be missed. [16]

Differential diagnoses

The differential diagnoses listed here are not exhaustive.

Treatment

Approach

Invasive treatment: TAA repair [13]

General indications

  • TAA rupture
  • Symptomatic TAA
  • Asymptomatic TAA when size or growth thresholds are passed

Indications for asymptomatic patients

The decision to perform elective TAA repair in asymptomatic patients depends on the size and expansion rate of the aneurysm. In all patients, the risks and benefits of aneurysm resection should be weighed carefully. [18]

Indications for TAA repair in asymptomatic patients [13]
Affected location of the aorta Aortic diameter
Ascending aorta
Aortic arch (isolated)
  • General threshold: ≥ 5.5 cm
  • Growth rate: > 0.5 cm/year
Descending aorta
  • Anatomic requirements for TEVAR are met: ≥ 5.5 cm
  • OSR required: ≥ 6 cm
  • Chronic dissection requiring OSR: ≥ 5.5 cm
  • Increased risk of rupture: Lower thresholds are reasonable.

Procedures [13]

Open surgical repair (OSR) is recommended for patients with TAA of the ascending aorta and aneurysms involving the aortic arch. For patients with descending thoracic or thoracoabdominal aortic aneurysms, thoracic endovascular aneurysm repair (TEVAR) or OSR can be performed.

Open surgical repair (OSR) [13]

Open surgical repair is a major operation with high associated morbidity and mortality. [18]

  • Indications: preferred in young patients with few comorbidities and low surgical risk and patients with connective tissue disorders [18]
  • Complications: 40% of all patients experience a perioperative complication [18]

Thoracic endovascular aneurysm repair (TEVAR) [13]

  • Indications: Degenerative or traumatic descending aortic aneurysms
  • Contraindications
    • Absence of a sufficiently long (2–3 cm) “landing zone” for the stent graft
    • Absence of adequate vascular access sites
  • Procedure: Under fluoroscopic guidance, an expandable stent graft is placed via the femoral or iliac arteries intraluminally at the site of the aneurysm.
  • Complications [13][19]
  • Other: requires lifelong postoperative surveillance

Additional procedures

Concomitant diseases may require additional procedures, e.g., CABG, valve replacement or repair.

  • Identify coronary anatomy and possible CAD before repair of the ascending aorta.
  • In end-organ ischemia or stenosis, ancillary revascularization is recommended.

Perioperative care

Surveillance after repair [15]

  • CTA chest abdomen pelvis with IV contrast
    • Initially: within the first month then at 3–12 months
    • Then every 6–12 months depending on the stability of findings
  • MRA chest/abdomen/pelvis with IV contrast: in patients with MR-compatible stent grafts (e.g., nitinol)

Conservative management

All patients should receive conservative treatment to reduce the risk of further aneurysm expansion or rupture. Regular aneurysm surveillance via CT or MR is recommended for patients in whom the diameter of the aneurysm has not reached the threshold defined as the indication for repair.

Reduction of cardiovascular risk factors [13]

Aneurysm surveillance

Follow-up frequency for surveillance of thoracic aortic aneurysm or dilatation via CT or MR [13]

Part of the aorta Maximum diameter of the aorta Recommended follow-up interval
Ascending aorta
  • 3.5–4.4 cm
  • 12 months
  • ≥ 4.5 cm
  • 6 months
Aortic arch
  • 3.5–3.9 cm
  • 12 months
  • ≥ 4 cm
  • 6 months
Descending aorta
  • 4–4.9 cm
  • 12 months
  • ≥ 5 cm
  • 6 months

Complications

We list the most important complications. The selection is not exhaustive.

Thoracic aortic aneurysm rupture

Risk factors [13]

Clinical features [13][16]

Diagnostics [13][16][15]

  • Initial evaluation
    • Hemodynamically unstable patients: no time for detailed assessment
      • Proceed directly to OR and consider bedside TTE.
    • Hemodynamically stable patients: Obtain CTA of the chest, abdomen, and pelvis with IV contrast.
      • Supportive findings
        • Extravasation of contrast
        • Contained rupture: perivascular hematoma sealed off by surrounding structures
        • Free rupture: massive hematoma
  • Additional diagnostic evaluation to consider (once patient has been stabilized)

Treatment

Acute management checklist for thoracic aortic aneurysm

  • Surgery consult
    • Immediate surgery consult for emergency repair if ruptured aneurysm is suspected → transfer to OR immediately.
    • Urgent surgery consult for repair if symptomatic but non-ruptured TAA is suspected → consider imaging for pre-procedural planning (if patient is hemodynamically stable).
  • NPO
  • IV access with two large-bore peripheral IV lines
  • Check CBC, type and screen, obtain patient consent for blood transfusion, and order pRBCs (prepare for massive transfusion protocol).
  • IV fluid resuscitation
  • Pain management
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last updated 07/22/2020
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