Key Facts

Thoracic aortic aneurysm (TAA) is abnormal dilatation of the thoracic aorta. It may involve the ascending aorta, aortic arch, or descending thoracic aorta. TAA may be asymptomatic for years but carries significant risk of rupture and dissection.

Epidemiology

• Incidence: ~6-10 per 100,000 per year
• Male:female ratio ~2-3:1
• Ascending aorta aneurysms account for ~60%
• Associated with connective tissue disorders in ~20% of cases

Aetiology

• Degenerative (medial degeneration): most common; associated with ageing, hypertension, atherosclerosis
• Connective tissue disorders: Marfan (FBN1), Loeys-Dietz (TGFBR1/2), Ehlers-Danlos type IV (COL3A1)
• Bicuspid aortic valve: BAV-associated aortopathy, even without significant valve disease
• Familial TAA (non-syndromic): ~20% familial; ACTA2, MYH11, SMAD3 mutations
• Aortitis: Takayasu, GCA, syphilitic (now rare)
• Post-dissection: chronic dissection with false lumen dilatation

Pathophysiology

• Cystic medial necrosis (medial degeneration): loss of smooth muscle cells and elastic fibres in media
• Wall weakening → progressive dilatation under arterial pressure (Laplace's law)
• Ascending aortic aneurysms: risk of dissection, AR, coronary compression
• Descending aortic aneurysms: risk of rupture, compression of adjacent structures (oesophagus, recurrent laryngeal nerve, bronchi)

Typical Presentation

• Most are asymptomatic — found incidentally on CXR, CT, or echocardiography
• Chest pain or back pain (dull, aching)
• Compression symptoms:
  • Hoarseness (recurrent laryngeal nerve compression — Ortner syndrome)
  • Dysphagia (oesophageal compression)
  • Stridor/cough (tracheal/bronchial compression)
  • SVC syndrome (SVC compression — rare)
• Aortic regurgitation (ascending aortic aneurysm with root dilatation)
• Heart failure from AR

Red Flags

• Acute onset severe chest/back pain (dissection or impending rupture)
• Rapid expansion on surveillance imaging
• Hoarseness or dysphagia with chest pain
• Known connective tissue disorder with chest pain

Bedside

• CXR: widened mediastinum, abnormal aortic contour, tracheal deviation
• ECG: LVH if associated AR or hypertension

Bloods

• FBC, U&Es, LFTs, coagulation: pre-operative assessment
• Genetic testing: Marfan (FBN1), Loeys-Dietz (TGFBR1/2), Ehlers-Danlos (COL3A1), familial TAA genes

Imaging

• CT angiography: gold standard for size, extent, anatomy, and surgical planning
• MR angiography: excellent for serial surveillance (avoids radiation)
• Echocardiography (TTE/TOE): aortic root and ascending aorta assessment, AR evaluation
• PET-CT: if aortitis suspected (metabolic activity in aortic wall)

Surveillance Intervals

Non-pharmacological

• Smoking cessation
• Avoid heavy isometric exercise (Valsalva manoeuvre increases aortic wall stress)
• Family screening: first-degree relatives of patients with familial TAA or connective tissue disorder

Pharmacological

• Beta-blockers: first-line to reduce aortic wall stress (reduce dP/dt)
  • Atenolol 25-100mg OD or bisoprolol
• ARBs (losartan): Marfan syndrome — may reduce TGF-β signalling and slow aortic root growth (COMPARE trial)
• Statins: cardiovascular risk management
• Antihypertensive therapy: target BP <130/80 mmHg

Surgical/Interventional

Ascending aortic aneurysm:

• Open surgical repair: graft replacement of ascending aorta ± aortic root (Bentall if Marfan)
• Thresholds:
  • ≥5.5 cm (degenerative)
  • ≥5.0 cm (BAV or familial TAA)
  • ≥4.5-5.0 cm (Marfan, Loeys-Dietz)
  • Rapid growth >0.5 cm/year
  • Operative mortality: ~3-5%

Descending aortic aneurysm:

• TEVAR (thoracic endovascular aortic repair): standard for descending TAA when suitable anatomy
• Open surgical repair: if TEVAR not suitable
• Threshold: ≥6.0 cm (or ≥5.5 cm with connective tissue disorder)

Referral Criteria

• All TAA approaching surgical thresholds: vascular/cardiothoracic referral
• Connective tissue disorder with aortic dilatation: specialist aortopathy clinic
• Symptomatic TAA: urgent referral
• Family screening: genetics clinic

• Small TAA (<5 cm): annual rupture risk <1%
• Large TAA (>6 cm): annual rupture/dissection risk ~5-15%
• Elective ascending aortic surgery: mortality ~3-5%
• Elective TEVAR (descending): mortality ~2-5%
• Rupture of TAA: mortality >80%
• Post-repair: good long-term survival; need lifelong surveillance
• Marfan patients: multiple operations may be needed over lifetime
• Genetic counselling and family screening reduce morbidity/mortality

Surgical Thresholds by Aetiology

Connective Tissue Disorder Red Flags