Thoracic and thoracoabdominal aortic aneurysms

Thoracic and Thoracoabdominal Aneurysms are defined as localized dilations involving all arterial layers, with a diameter exceeding >50% of the adjacent segment or reference norms (which vary based on location). They are three times less common than abdominal aortic aneurysms, but unlike the latter, they occur equally in men and women, with the incidence increasing with age (peaking between 60 and 70 years in developed countries). Unfortunately, they are often asymptomatic or show few symptoms, except in cases of complications, and are usually discovered incidentally or during complications.

Their progression, without treatment or in the event of complications, is generally fatal, and mortality remains high even with appropriate care.

Etiologies and Risk Factors

  See detailed article: Arterial aneurysms

These are the same as for any arterial aneurysm. However, thoracic aortic aneurysms are overwhelmingly of atherosclerotic origin. Any case discovered in a patient under 50 years old or associated with unexplained systemic or neurological signs should raise suspicion of an inflammatory aneurysm, particularly syphilitic, or collagen abnormalities.

Classification

Thoracic aortic aneurysms are classified based on location: ascending aorta, aortic arch, and descending aorta (type A = above the 6th rib, type B = below the 6th rib, type C = A+B), and thoracoabdominal aneurysms.

Clinical Presentation

They are generally asymptomatic in the uncomplicated stage, though they can rarely cause back and/or interscapular pain.

In case of complications, the following symptoms may appear:

• Compression of neighboring structures: dysphagia, cough, dyspnea, bronchopneumonia, atelectasis, Claude-Bernard-Horner syndrome, etc.
• Dissection or rupture: intense pain, hemoptysis, shock, hemothorax, hematemesis, spinal cord syndrome, sudden death, etc.
• Thromboembolism: focal neurological deficits, limb ischemia, abdominal pain, etc.
• Aortic insufficiency: heart failure

Natural History and Prognosis

Diameter growth is highly variable but averages 3 to 5 mm per year, depending on initial size, the presence of a parietal thrombus, and the location on the descending aorta. The risk of rupture, the main cause of mortality, depends on wall tension = Pressure x Radius / Wall thickness (Laplace’s Law). Risk factors include:

• Maximal diameter:
  • A rupture risk is typically considered for diameters >6 cm (ascending aorta) or >7 cm (descending aorta).
  • A rupture risk is considered for diameters >5 cm in specific cases such as Marfan syndrome.
• The one-year mortality for a thoracic aortic aneurysm considered at risk of rupture, without treatment, is 35%, and the five-year mortality is 80%.
• Rapid increase in diameter
• Uncontrolled hypertension

Complications

  See detailed article: Thoracic aortic dissections

Ischemic Strokes, Spinal Cord Infarctions, Mesenteric Infarction, Ischemic Colitis and Abdominal Angina, Acute Limb Ischemia, Valvulopathies - Aortic Insufficiency

• Aortic dissection and rupture:
  • These are the most dramatic complications and are absolute medical-surgical emergencies.
  • Aortic rupture is rapidly fatal without surgical treatment. Nearly 50% of patients die before reaching the hospital. Among those operated on, 40-50% will die within a month post-operatively.
  • Untreated aortic dissection results in 90-95% mortality at one year (mostly from rupture). About 20% of patients die before reaching the hospital. Among those operated on, in-hospital mortality ranges from 10-30%. One-year mortality among survivors is 40-50%.

• Thromboembolism (ischemic strokes and spinal infarctions, renal infarctions, mesenteric infarctions, peripheral embolism, etc.)
• Aortic valve insufficiency
• Compression of neighboring structures
• Potential complications specific to the underlying etiology

Additional Examinations

Apart from dissection (see management of dissection), the minimum workup includes a cardiac ultrasound and angiographic examination.

• Chest X-ray:
  • Can suggest an aneurysm based on mediastinal widening or aortic arch enlargement.
  • This test is neither sensitive nor specific and is not indicated for screening or diagnostic purposes.
  • However, it is often the origin of incidentally discovered asymptomatic aneurysms (to be confirmed by other imaging types).

• Cardiac Ultrasound
  • Transthoracic:
    • Performs well for assessing the size, extension, and functional impact of the aneurysm, but does not visualize the descending aorta.
  • Transesophageal:
    • Better performance and allows visualization of the descending aorta.
• Angio-CT scan or Angio-MRI:
  • Highly effective for assessing the aneurysm structure and surrounding tissues. Although less well established, Angio-MRI (non-irradiating) tends to replace the Angio-CT scan. The choice depends on the expertise level of the reference center.
• Conventional Angiography:
  • The best exam for assessing the arterial lumen. However, its indications have become rare (due to the strong performance of alternatives and the semi-invasive nature of the exam with risks of thromboembolism and nephropathy), except for endovascular treatments.
• Systematic syphilitic serology in cases of ascending aortic aneurysm
• Other exams (biological tests, PET-CT scans, etc.) are useful only for etiological investigation and should be considered depending on the clinical context (young patients, family history, systemic signs, etc.).

Therapeutic Management of Non-Dissected, Non-Ruptured Aneurysms

Indications for surgical or endovascular treatment (graft or endograft):

• Symptomatic or complicated aneurysms
• Aneurysms with a diameter >6 cm (>5 cm in Marfan syndrome). Some consider a threshold of 5 cm for the ascending aorta and 7 cm for the descending aorta.
• Infectious aneurysms

Overall operative mortality is 10% within one month (+ morbidity of 10-20%: thromboembolism, spinal cord injury, renal failure, etc.) and 50% at ten years.

Treat the underlying cause where applicable (antibiotic therapy, corticosteroids, etc.).

Strict control of blood pressure.

Therapeutic Management of Dissected or Ruptured Aneurysms

  See detailed article: Thoracic aortic dissections

This is an absolute medical-surgical emergency and is addressed in a dedicated chapter.

Bibliography

Black JH et al., Epidemiology, risk factors, pathogenesis, and natural history of thoracic aortic aneurysm and dissection, UpToDate, 2024

Burke CR, Clinical manifestations and diagnosis of thoracic aortic aneurysm, UpToDate, 2024

Burke CR, Management of thoracic aortic aneurysm in adults, UpToDate, 2024

EMC, Traité d'Angéiologie, 2018