Thoracic aortic aneurysm management

Thoracic aortic aneurysm management

Thoracic aortic aneurysm management

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🧬 Pathophysiology - The Wall Weakens

The aortic wall weakens from degradation of structural proteins (elastin, collagen), leading to dilation. Governed by Laplace's Law, wall tension increases with radius ($T = P \times r$), promoting further expansion.

  • Degenerative (Most Common):
    • Atherosclerosis: Chronic inflammation damages intima and media.
    • Cystic Medial Necrosis: Fragmentation of elastic fibers in the media; common with aging.
  • Genetic/Connective Tissue Disorders:
    • Marfan Syndrome: Defective fibrillin-1 (FBN1).
    • Ehlers-Danlos Syndrome (Vascular): Defective type III collagen.
  • Other:
    • Infections: Syphilitic aortitis, mycotic aneurysms (Staph, Salmonella).
    • Trauma: Deceleration injury.

Marfan syndrome is classically associated with cystic medial necrosis, predisposing to aortic root aneurysm and dissection.

Aortic wall histology: Nondilated vs. Aneurysm

🤫 Clinical Manifestations - The Silent Threat

Most are asymptomatic and discovered incidentally. When symptoms occur, they are due to expansion, compression, or rupture.

  • Pain: Most common symptom. Typically a deep, steady, severe pain in the chest or back.
  • Compression of adjacent structures:
    • Hoarseness: Left recurrent laryngeal nerve palsy.
    • Dysphagia: Esophageal compression.
    • Stridor/Cough: Tracheal or mainstem bronchus compression.
    • SVC Syndrome: Edema of the face/neck/arms, JVD.

⭐ Hoarseness from a TAA is a classic sign of left recurrent laryngeal nerve compression (Ortner's syndrome), a frequently tested association.

🩺 Diagnosis - Seeing the Bulge

  • Initial Test: Chest X-ray (CXR) is often the first clue, showing a widened mediastinum or an enlarged aortic knob.
  • Gold Standard: CT Angiography (CTA) is the definitive diagnostic tool.
    • Details aneurysm size, location, and branch vessel involvement.
    • Essential for pre-operative planning (Open vs. TEVAR).
  • Alternatives:
    • MRA: For stable patients with contraindications to CTA (e.g., severe contrast allergy, renal failure).
    • TEE: Useful for unstable patients or intra-operative assessment.

⭐ CTA is not just for diagnosis; it's the essential roadmap for planning repair, determining suitability for endovascular (TEVAR) vs. open surgery.

🔪 Management - Cut or Watch?

  • Medical Management (Watch): Goal is to ↓ aortic wall stress & slow expansion.
    • BP Control: Target SBP 100-120 mmHg.
    • Agents: β-blockers (first-line); ARBs (especially for Marfan syndrome).
    • Surveillance: Serial imaging (CT/MRI) every 6-12 months.

⭐ Beta-blockers are key as they decrease the rate of change of blood pressure ($dP/dt$), reducing aortic shear stress beyond just lowering the absolute BP.

  • Surgical Intervention (Cut): Decision based on size, growth rate, or symptoms.

💥 Complications - When the Wall Breaks

  • Rupture: Catastrophic hemorrhage (hemothorax, hemopericardium).
    • Presents with sudden pain, profound hypotension, and shock.
  • Dissection: Intimal tear creates a false lumen.
    • Presents with new, severe, "tearing" chest or back pain.
    • Leads to malperfusion syndromes (stroke, MI, limb ischemia).

⭐ Rupture is a surgical catastrophe with pre-hospital mortality >80%. Immediate intervention is the only chance for survival.

⚡ Biggest Takeaways

  • Ascending TAA is linked to Marfan syndrome and cystic medial necrosis; descending TAA to atherosclerosis.
  • Often asymptomatic; symptoms from compression (hoarseness, dysphagia) or chest/back pain.
  • CT angiography (CTA) is the diagnostic gold standard for planning repair.
  • Repair ascending TAA at >5.5 cm (or >4.5 cm in Marfan).
  • Repair descending TAA at >6.0 cm, often with endovascular repair (TEVAR).
  • Medical therapy: strict blood pressure control with beta-blockers to slow growth.

Practice Questions: Thoracic aortic aneurysm management

Test your understanding with these related questions

A 72-year-old woman comes to the physician for follow-up care. One year ago, she was diagnosed with a 3.8-cm infrarenal aortic aneurysm found incidentally on abdominal ultrasound. She has no complaints. She has hypertension, type 2 diabetes mellitus, and COPD. Current medications include hydrochlorothiazide, lisinopril, glyburide, and an albuterol inhaler. She has smoked a pack of cigarettes daily for 45 years. Her temperature is 37°C (98.6°F), pulse is 90/min, respirations are 12/min, and blood pressure is 145/85 mm Hg. Examination shows a faint abdominal bruit on auscultation. Ultrasonography of the abdomen shows a 4.9-cm saccular dilation of the infrarenal aorta. Which of the following is the most appropriate next step in management?

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Flashcards: Thoracic aortic aneurysm management

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EF < _____% and MI within _____ months are absolute contraindications to non-cardiac surgery

TAP TO REVEAL ANSWER

EF < _____% and MI within _____ months are absolute contraindications to non-cardiac surgery

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