81. Aneurysms. Dissections of the aorta.

Question 1

Aneurysm (definition, classification, complications)

Answer 1

definition: ballon like dilation of the blood vessels or heart chamber.

can be true (involving all 3 layers of artery) or false (extravascular hematoma in communication with intravascular hematoma)

classification: saccular (portion) or fusiform (circumferential)

complication:

1. stasis –> thrombosis –> embolism
2. rupture –> hemorrhage
3. compression and obstruction of nearby structures

Question 2

Aneurysm (pathogenesis)

Answer 2

weakness of artery’s medial layer

acquired:
1. atherosclerosis
2. hypertension
3. infection
4. vasculitis

inherited
1. abnormal CT synthesis
a. Marfan syndrome: defects in synthesis of fibrillin –>
dysregulation of TGF-beta signaling and loss of
elastic tissue
b. Type 4 Ehlers Danlos syndrome: type 3 collagen
synthesis defect
c. TGF-beta receptor mutation: no SMC proliferation
and ECM synthesis –> defective elastin and
collagen synthesis

2. excessive CT degradation: matrix metalloproteases secreted by macrophages in atherosclerotic plaque
3. loss of SMCs: atherosclerotic thickening of intima can cause ischemia of media

Question 3

types of aneurysms

Answer 3

1. thoracic aneurysm
   cause: tertiary syphilis- infects vasovasorum –> decreased blood flow –> atrophy of vessel wall –> aneurysm
   complication: aortic insufficiency (dilation of aortic valve root)
2. abdominal aneurysm
   cause: atherosclerosis
   complication: rupture, obstruction

Question 4

Dissection of aorta (definition, complication)

Answer 4

definition: pressured blood enters the blood vessel wall separating between the various layers

complications:
1. rupture: into pericardium (tamponade) or into mediastinum (fetal hemorrhage)

2. obstruction of vessels: compression of coronary arteries (MI)

Question 5

Dissection of aorta (pathogenesis)

Answer 5

Weakening of media

1. hypertension: hyaline arteriosclerosis of small vessels of vasavasorum —> ischemia –> atrophy of SMC –> dissection (older ppl)
2. inherited defect of CT (like marfan or Ehlers Danlos syndrome)

Question 6

Dissection of aorta (types)

Answer 6

Type A dissection (proximal lesion)
DeBakey type 1: w/ involvement of descending aorta
DeBakey type 2: without involvement of descending aorta

Type B dissection (distal lesion) aka DeBakey 3: distally to subclavian artery