Vascular: Aortic Dissection

Question 1

what is an aortic dissection? how does it progress?

Answer 1

Tear in intimal layer of aortic wall causing blood to flow between the layers, splitting them apart.
Dissection can then progress distally, proximally or both:
- anterograde dissection: towards iliac arteries
- retrograde dissection: towards aortic valve

Can be acute (Dx <14 days) or chronic (Dx >14 days).

Question 2

suggest risk factors for aortic dissection

Answer 2

• HTN: increased pressure
• atherosclerosis
• male
• caucasian
• connective tissue disorders (e.g. Marfan’s, Ehlers-Danlos): weakened aortic wall
• bicuspid aortic valve

Question 3

describe the DeBakey classification of thoracic aortic dissections

Answer 3

Type I

• originates in ascending aorta and propagates at least to aortic arch
• typically seen in <65 yrs, carries highest mortality

Type II

• confined to ascending aorta
• typically seen in elderly pts with atherosclerosis and HTN

Type III

• originates in descending aorta to L of subclavian artery
• IIIa: extends to diaphragm; IIIb: extends beyond diaphragm into abdo. aorta

Question 4

describe the Stanford classification of thoracic aortic dissections

Answer 4

Group A:

• involves ascending aorta, aortic arch and can propagate to descending aorta
• includes DeBakey Type I and II

Group B:

• does not involve ascending aorta
• includes DeBakey Type III

Question 5

Describe the signs and symptoms associated with thoracic aortic dissection

Answer 5

Symptoms:

• tearing or stabbing chest pain
• can radiate depending on anatomy of dissection, esp. to back

Signs:

• tachycardia
• hypotension (secondary to hypovolaemia from blood loss into dissection, or cardiogenic from severe aortic regurgitation or pericardial tamponade)
• new aortic regurgitation murmur
• signs of end-organ hypoperfusion, e.g. decreased UO, deteriorating conscious level
• +/- neurological sequelae of dissection, e.g. paraplegia

Question 6

which investigations would you perform on a pt with suspected dissection?

Answer 6

Bedside tests:
1. ECG - to exclude cardiac pathology

Bloods:

2. Baseline: FBC, UandE, LFTs, troponin, coagulation
3. Cross-match: at least 6 units

Imaging:

4. CT angiogram: for Dx and classification of dissection
5. Transoesophageal echo: can provide useful info about thoracic aorta

Question 7

describe your initial Mx of a pt with dissection

Answer 7

1. O2 15L/min
2. IV access and fluid resus (maintain systolic at 100-120 mmHg - permissive hypotension)
3. catheterise
4. contact vascular surgeon ASAP

Question 8

describe your definite Mx of a pt with dissection

Answer 8

Stanford type A (worse prognosis): surgical removal of ascending aorta (+/- arch) and replacement with synthetic graft. May need aortic valve repair.

Stanford type B: can usually be managed medically, e.g. treatment of any HTN with beta blockers. Surgical intervention (e.g. endovascular stent graft) determined on basis of complications.

Question 9

describe the long-term Mx of a pt with dissection

Answer 9

All pts need lifelong HTN therapy and surveillance imaging due to high risk of further dissection or other complications. E.g. imaging at 1, 3 and 12 mths after discharge with further scans at 6-12 mth intervals depending on size of aorta.

Question 10

describe possible complications of dissection

Answer 10

Depends on site and spread of dissection. Mortality remains high, with >20% dying before reaching hospital.

1. aortic rupture
2. aortic valve prolapse
3. bleeding into pericardium and cardiac tamponade
4. MI secondary to coronary artery dissection
5. stroke or paraplegia secondary to cerebral artery or spinal artery involvement