Aortic dissection

Question 1

Define aortic dissection and summarise its epidemiology

Answer 1

Defintion: A condition where a tear in the aortic intima allows blood to surge into the aortic wall, causing a split between the inner and outer tunica media, creating a false lumen.

Classification (Stanford):
Type A: ASCENDING aorta (MOST COMMON)
Type B: DESCENDING aorta (distal to the left subclavian artery)

Epidemiology: Most common in men between 40 and 60 years.

Question 2

Summarise the aetiology/risk factors of aortic dissection

Answer 2

• Degenerative changes in the smooth muscle of the aortic media are the predisposing event.
• Common causes and predisposing factors are:
  • Hypertension
  • Aortic atherosclerosis
  • Connective tissue disease (e.g. SLE, Marfan’s, Ehlers–Danlos)
  • Congenital cardiac abnormalities (e.g. aortic coarctation)
  • Aortitis (e.g. Takayasu’s aortitis, tertiary syphilis)
  • Iatrogenic (e.g. during angiography or angioplasty)
  • Trauma
  • Crack cocaine.

Question 3

Describe the history/presenting symptoms of aortic dissection

Answer 3

• Present with sudden central ‘tearing’ pain, may radiate to the back (may mimic an MI).
• Aortic dissection can lead to occlusion of the aorta and its branches:
  • Carotid obstruction: Hemiparesis (weakness on one side), dysphasia, blackout.
  • Coronary artery obstruction: Chest pain (angina or MI).
  • Subclavian obstruction: Ataxia, loss of consciousness.
  • Anterior spinal artery: Paraplegia.
  • Coeliac obstruction: Severe abdominal pain (ischaemic bowel).
  • Renal artery obstruction: Anuria, renal failure.

Question 4

What are the signs of aortic dissection upon physical examination?

Answer 4

• Murmur on the back below left scapula, descending to abdomen.
• Blood pressure (BP): Hypertension (BP discrepancy between arms of >20mmHg), wide pulse pressure.
• Hypotension may sugest tamponade:
  • check for pulsus paradoxus = abnormally large decrease in systolic blood pressure and pulse wave amplitude during inspiration.
• Signs of aortic regurgitation/insufficiency:
  • High volume collapsing pulse
  • Early diastolic murmur over aortic area
• Unequal arm pulses.
• There may be a palpable abdominal mass.

Question 5

What investigations are used to identify aortic dissection? Interpret the results of such investigations

Answer 5

- Bloods: 
    • FBC
    • Cross-match 10 units of blood
    • U&E (renal function)
    • Clotting. 

• CXR: Widened mediastinum, localized bulge in the aortic arch.
• ECG:
  • Often normal.
  • Signs of left ventricular hypertrophy or inferior MI if dissection compromises the ostia of the right coronary artery.
• CT-thorax: False lumen of dissection can be visualized.
• Echocardiography: Transoesophageal is highly specific. Allows visualisation
• Cardiac catheterization and aortography.