7.4 Aortic Dissection and Aneurysm

Question 1

Most common causes of aortic dissection, and pathogenesis.

Answer 1

Aortic dissection occurs due to intimal tear with dissection of blood through media due to HTN and preexisting weakness of the media. Weakness is caused by:

Hypertension (older): HTN causes hyaline arteriolosclerosis of the vasa vasorum leading to atrophy of the media

Marfan and Ehlers-Danlos are connective tissue issues leading to wall thickness

Question 2

What is the most common cause of death with aortic dissection?

Answer 2

Pericardial tamponade

Others: hemorrhage, obstruction of vessels (coronary, renal)

Question 3

Most common cause and main features of thoracic aortic aneurysms

Answer 3

Common with tertiary syphilis which causes endarteritis leading to vasa vasorum narrowing and atrophy of the medial layer. Results in tree-bark appearance
Major complication is dilation of aortic valve root leading to insufficiency.
Can also compress other mediastinal structures.

Question 4

Pathogenesis of abdominal aortic aneurysm

Answer 4

Atherosclerosis is most common cause in men over 60 with smoking history and HTN.
Atherosclerosis thickens the wall which inhibits blood and O2 diffusion leading to wall damage and weakening.

Question 5

What is the triad that AAA presents with?

Answer 5

hypotension, pulsatile mass, flank pain

Question 6

Does a dissecting aorta usually have high, low, or normal BP?

Answer 6

Often normal or elevated

AAA rupture has low BP

Question 7

Why do aortic dissections tend to happen in the proximal 10cm of the vessel?

Answer 7

The most proximal portion has high stress from the blood pressure coming straight out of the heart. To handle this requires a thick wall that prevents good O2 diffusion and thus the adventitia of very muscular arteries is provided by the vasa vasorum which is susceptible to hyaline arteriolosclerosis leading to narrowing and ischemia.