Aortic Dissection

Question 1

What is aortic dissection?

Answer 1

refers to the disruption of the medial layer of the aorta due to blood, leading to separation of the layers resulting in a true lumen and false lumen. As this false lumen fills with blood, it may propagate proximally or distally. This results results in either rupture through the adventitia or re-entry to the true lumen via a second intimal tear.

Question 2

What are the two classification systems of aortic dissection? and explain them.

Answer 2

Stanford and DeBakey

Stanford:
Type A- ascending aorta is involved
Type B- Ascending aorta is not involved

DeBakey:
Type I- involves the ascending aorta, dissection extends into arch and beyond
Type II- limited to the ascending aorta
Type IIIa- involved the descending thoracic aorta
Type IIIb- Involves descending thoracic aorta and abdominal aorta

Question 3

What three layers make up the aorta? What happens in aortic dissection?

Answer 3

1) Tunica intima: Inner-most layer composed of endothelium and a subendothelial layer of connective tissue.
2) Tunica media: Middle layer, provides strength and elasticity. Composed of smooth muscle, elastic fibres and collagen.
3) Tunica adventitia: Outer layer, composed mainly of collagen as well as the vasa vasorum and lymphatics.

• Aortic dissection most commonly occurs when an intimal tear allows blood to enter the intima-media space. This leads to the formation of a false lumen. Blood may propagate proximally or distally to the intimal tear.

Question 4

What are the congenital causes of aortic dissection?

Answer 4

• Connective tissue disorders (Marfan’s syndrome, Ehlers Danlos syndrome, Osteogenesis imperfecta)
• Turner’s syndrome
• Noonan’s syndrome
• Bicuspid aortic valve
• Metabolic disorders

Question 5

What are some acquired causes of aortic dissection?

Answer 5

• Arterial hypertension
• Syphilitic aortitis
• Pregnancy
• Trauma
• Iatrogenic (surgical; aortic cannulation, aortic cross-clamp)
• Cocaine use

Question 6

What are some complications of aortic dissection?

Answer 6

• cardiac tamponade
• aortic regurgitation

Question 7

What are the symptoms of aortic dissection?

Answer 7

• chest pain (classically tearing and maximally at onset, though frequently this is not seen)
• back pain
• abdominal pain
• dypnea
• syncope/collapse

Question 8

What are some signs of aortic dissection?

Answer 8

• intra-arm blood pressure differential
• neurological deficit
• horner’s syndrome
• absent peripheral pulses

Question 9

What are the signs (triad) of cardiac tamponade and acute aortic regurgitation?

Answer 9

CT:
- Raised JVP
- Muffled heart sounds
- Hypotension

ACR:
- diastolic murmur
- wide pulse pressure
- signs of HF

Question 10

What investigations would you do for aortic dissection?

Answer 10

• ECG (ischemic changes may present if dissection interferes with coronary blood flow)
• FBC
• U&Es
• LFTs
• Clotting Screen
• D-Dimer
• Troponin (maybe elevated if their involvement of coronary vessels)
• ABG/VBG
• Group & save/cross-match
• CXR- may demonstrate a widened mediastinum and left-sided pleural effusion (leaking dissection). Not definitive imaging and may appear normal.
• CT angiogram-Considered definitive imaging in suspected dissection
• MRI- May be used in renal failure or those with iodine allergies. Disadvantages include it being less available and images take longer to acquire. Often used in the follow-up of patients with chronic dissections or following repair.
• Echo- Transthoracic echocardiogram may be useful in the assessment of dissections of the ascending aorta. Additionally may be used to evaluate for aortic regurgitation and cardiac tamponade.

Question 11

What is the management of Stanford type A aortic dissection?

Answer 11

emergency surgery is indicated in suitable patients. It carries a mortality of 50% in the first 48 hours in those not undergoing surgical intervention. Endovascular repair has been used but is not yet validated in the management of acute type A aortic dissection.

Question 12

What is the management of Stanford type B aortic dissection?

Answer 12

In patients with uncomplicated Stanford B dissections, medical management remains the treatment of choice. This involves blood pressure management and appropriate analgesia. Thoracic endovascular aortic repair (TEVAR) may be used in patients with Stanford B dissections with suitable anatomy.

Emergency or urgent surgery may also be indicated in Stanford type B dissections with:

• Intractable pain
• Rupture or evidence of impending rupture
• End-organ damage or limb ischaemia
• Rapid progression
• Marfan’s syndrome