Aortic Dissection

Question 1

What is an aortic dissection?

Answer 1

An aortic dissection is a life-threatening condition where there is separation of the layers in the wall of the aorta.

Question 2

Name the 3 layers of the aorta wall?

Answer 2

The aorta wall has 3 layers (as do all arteries):

1. Tunica adventitia – thin outer layer
2. Tunica media – thick middle layer
3. Tunica intima – think inner layer.

Question 3

How does an aortic dissection occur?

Answer 3

The aortic wall is exposed to high stress and pressure from the ventricular pressure and disruptions and damage can occur i.e. aortic dissection. In aortic dissection, the tunica intima is damaged, and blood enters the space between intima and media. The blood collects here and continues to shear away the connection between intima and media (peels away the intima layer).

As blood continues to enter between the layers, the dissection expands, and the wall will become bulged. Two processes can then occur:

1) Blood can continue to separate the intima and media for a larger length of the aorta (propagation). This will continue and result in severe blood loss into the dissection and will reduce the blood flow around the body = HTN and shock
2) An exit tear can develop, and blood can re-enter the lumen

In an aortic dissection there is a true lumen (between tunica intima and tunica intima) and a false lumen (between tunic intima and tunica media).

Question 4

What are the causes of an aortic dissection?

Answer 4

1. Chronic hypertension – stress and degenerative changes
2. Connective tissue disease – Marfan’s syndrome, Ehlers Danlos syndrome
3. Aneurysm
4. Trauma
5. Men (3:1)
6. Age (50-65 years)

Question 5

What are the two types of aortic dissections?

Answer 5

Type A – involve any part of the aorta BEFORE the origin of the left subclavian artery, require surgery

Type B – involve any part of the aorta AFTER the origin of the left subclavian artery, medically treated

Question 6

Where do aortic dissections commonly occur?

Answer 6

– 2cm above the aortic root
– Just after the left subclavian artery
– Within 10 cm of the aortic valve (90%)

These areas are the most common as they have the greatest pressure and are more likely to be damaged. The blood is more turbulent at the proximal aorta as it needs to change direction (ascend, arch and then descend)

Question 7

what are the symptoms of an aortic dissection?

Answer 7

– Sudden severe central chest pain radiating to the back
– ‘Tearing’ sensation
– Sweating
– Nausea
–Dyspnoea
– Weakness
– Syncope
– Abdominal pain (if abdominal dissection)

Question 8

How is an aortic dissection diagnosed?

Answer 8

1. History and exam
2. Investigations to locate aortic dissection
   a. Transoesophageal echocardiogram (quick and cheap, but unable to view abdominal aorta)
   b. CT with contrast (Gold standard, can image the entirety of the aorta)
   c. MR angiogram (100% sensitive and specific)