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