Aneurysms and Dissection

Question 1

describe a true vs. false aneurysm

Answer 1

• true aneurysm:
  
  • involve the 3 layers of the vessel wall
  • the blood remains within the confines of the circulatory system
  • atherosclerotic, syphilitic, congenital aneurysm
• false (pseudoaneurysm)
  
  • is an extravascular hematoma that communicates with the intravascular space

Question 2

describe a fusiform aneurysm

Answer 2

• fusiform:
  
  • diffuse, circumferential dilations of a long vascular segment, more common than saccular

Question 3

describe a saccular aneurysm

Answer 3

• saccular:
  
  • spherical outpouchings involving only a portion of the vessel wall
  • often contain thrombus

Question 4

the most common site of an atherosclerotic aneurysm is the _____

Answer 4

the most common site of an atherosclerotic aneurysm is the abdominal aorta

Question 5

describe the pathogenesis of atherosclerotic aneurysm

Answer 5

• local MMPs produced by macrophages degrade all the components of ECM in the arterial wall; collagen, elastin, proteoglycans, laminin, fibronectin
• deficiency of tissue inhibitor of proteinases

Question 6

atherosclerotic aneurysm pathogenesis:

_____ produced by macrophages degrade all the components of the ECM; this is caused by a deficiency of _____

Answer 6

local MMPs produced by macrophages degrade all the components of the ECM; this is caused by a deficiency of tissue inhibitor of proteinases

Question 7

describe the gross and histological changes seen in atherosclerotic aneurysms

Answer 7

• gross:
  
  • most are distal to renal arteries and prox. to the bifurcation
  • usually fusiform, may be saccular
  • majority are lined by raised, ulcerated, and calcified (complicated) atherosclerotic lesions
• histo:
  
  • reveals destruction of the normal arterial wall and its replacement by fibrous tissue
  • thickened and focally inflamed adventitia

Question 8

describe the clinical course of an atherosclerotic aneurysm

Answer 8

• many aneurysms are asymptomatic
• abdominal mass
• occlusion of a branch vessel (renal, mesenteric, vertebral vessels)
• embolism from atheroma or mural thrombus
• impingement on an adjacent structure
  
  • compression of ureter or erosion of vertebrae

Question 9

the risk of rupture of an atherosclerotic aneurysm is related to _____ and can be secondarily infected by ____

explain this

Answer 9

the risk of rupture of an atherosclerotic aneurysm is related to size and can be secondarily infected by Salmonella

• 25-40% for aneurysms larger than 6 cm
• can be secondarily infected by Salmonella
  
  • complication of mycotic aneurysm

Question 10

syphilitic aneurysms usually affect the _____

explain this

Answer 10

syphilitic aneurysms usually affect the thoracic aorta

• the inflammatory response to the bacteria → obliterative endarteritis of the vasa vasorum of the aorta → narrowing of their lumen → ischemic injury of the elastic tunica media in the aorta → medial destruction and weakening followed by chronic inflam. and scarring

Question 11

describe the morphology of syphilitic aneurysms

Answer 11

• fibrosis of the vascular wall can give involved vessels a tree bark appearance
• wrinkling of aortic intima due to secondary atherosclerosis may narrow or occlude coronary ostea
• aortic valve ring dilation, resulting in valvular insufficiency
• aortic valvular insufficiency → massive hypertrophy of LV referred as cor bovinum (cow’s heart)

Question 12

describe the clinical course of syphilitic aneurysms

Answer 12

• encroachment on the mediastinal structures:
  
  • resp. difficulties
  • diff. in swallowing
  • persistent cough → recurrent laryngeal n. compression
• pain caused by erosion of the ribs or vertebrae
• aortic incompetence → LVH → CHF (most common cause of death)
• cardiac ischemia due to obstruction to coronary ostia
• rupture of the aneurysm

Question 13

describe congenital aneurysms caused by Marfan Syndrome

Answer 13

• AD mutation in the gene fibrillin-1
  
  • required for normal elastic tissue development
• other features of Marfans Syndrome
  
  • skeletal abnormalities
    
    • elongated axial bones, very tall and slender
    • lower body is more than upper body length
    • long thin extremities and finger
  • ocular findings
    
    • subluxation of the lens (ciliary body is rich in fibrillin)

Question 14

Answer 14

Question 15

describe Berry aneurysm

Answer 15

• developmental thin-walled aneurysms in the circle of Willis (anterior cerebral artery branches)
• develop over time because the arterial media is congenitally attenuated
• rupture at any time but often during increased intracranial pressure → subarachnoid hemorrhage → severe headache, coma
• associated with polycystic kidney disease

Question 16

Berry aneurysms are associated with _____

Answer 16

Berry aneurysms are associated with polycystic kidney disease

Question 17

list the most common sites of Berry aneurysms

Answer 17

Question 18

describe an aortic dissection

Answer 18

• entry of blood in between and along the laminar planes of media and its extension along the length of the vessel
• often rupture causing massive hemorrhage

Question 19

describe the 2 groups of people commonly affected by aortic dissection

Answer 19

• commonly seen in 2 groups of people:
  
  • 40-60 years old with HTN (90% of cases)
  • younger population w/ CT disease
    
    • e.g. Marfans

Question 20

describe the etiopathogenesis of aortic dissection (4)

Answer 20

• hypertension:
  
  • HTN → hypertrophy of vasa vasora (causing narrowing) → ECM degenerative changes and variable loss of medial smooth muscle cells (pressure and ischemia both play a role)
• abnormality of CT:
  
  • Marfan’s syndrome, ED syndrome
• complication of arterial cannulation:
  
  • e.g. during diagnostic catheterization or cardiopulmonary bypass
• pregnancy induced
  
  • hormone-induced vascular remodeling
  • perinatal hemodynamic stresses

Question 21

describe the proximal lesions (Type A) vs. distal lesions (Type B) in aortic dissections

Answer 21

• proximal lesions (Type A)
  
  • more common, involve the ascending aorta
  • high mortality
  • needs rapid medical and surgical treatment
• distal lesions (Type B)
  
  • involve the descending aorta distal to the left subclavian artery
  • better prognosis, can be managed conservatively

Question 22

describe clinical features of aortic dissection

Answer 22

• sudden onset chest pain:
  
  • tearing in nature
  • radiates to the back (felt between scapulae) and moving down as the dissection progress
• loss of one or more arterial pulses

Question 23

describe the gross morphological changes seen in aortic dissection

Answer 23

• gross:
  
  • intimal tear, transverse, sharp, jagged
  • it separates the inner 2/3 of the aorta from the outer 1/3
  • external rupture → hemorrhage, tamponade
  • rupture into the lumen → double-barreled aorta

Question 24

describe the histological changes seen in the aortic dissection

Answer 24

• cystic medial degeneration: lesions consists of focal loss of elastic & muscle fibers in the media → cystic spaces filled with a myxoid material
• inflammation is absent

Question 25

Answer 25