Outline the advantages and disadvantages of a CT scan, transoesophageal echocardiography (TOE), MRI and an aortogram for the evaluation of suspected aortic dissection.

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College Answer

CT

Advantages:

  • Easy availability on an emergency basis
  • High sensitivity and specificity
  • Can pick up complications involving the branches ( e.g. ischaemic gut) and
  • extent of dissection into abdominal aorta
  • Easier to monitor the patient than MRI
  • Detects pericardial effusion.

Disadvantages:

  • Have to move the patient
  • Iodinated contrast
  • Cannot assess for AR, LV function or coronaries

TOE

Advantages:

  • Bedside test
  • Can detect intimal flap, true and false lumen AR, tamponade
  • Assess LV function
  • No contrast needed

Disadvantages:

  • Semi - invasive
  • May need anaesthesia/intubation
  • May cause undesirable hypertension
  • “Blind spot” arising from left main bronchus
  • Not widely available
  • Special expertise required

MRI

Advantages:

  • High sensitivity and specificity
  • MR contrast (Gadolinium) has more favourable safety profile
  • Can detect AR

Disadvantages:

  • Not readily available
  • Inconvenient (patient motionless for 30 minutes)
  • Access and monitoring difficult, esp. for haemodynamically unstable patient on IV infusions
  • Limited applicability (claustrophobia, pacemakers etc. )

Aortography

Advantages:

  • Will detect intimal flap, AR
  • Assess LV, tamponade, blocked coronaries (important for surgery in type A dissection)

Disadvantages:

  • Not readily available
  • Invasive
  • Large contrast load