Dissecting aneurysm

• dissection is an intimal tear with hemorrhage into the wall of the vessel

• most often occurs in the thoracic aorta

• two main groups at risk

  • hypertensive men, 40-60 years old

  • people with connective tissue disorders (e.g. Marfan syndrome)

• hypertension is present in 94% of cases

• technically a type of false aneurysm

Grossly

• there is a little transverse tear spreading from the aortic valve

• another specimen: carotid has blood accumulating in the media and compressing the lumen

Sequence of events

• intimal tear

• hemorrhage into aortic media

• extension of hemorrhage

• rupture

Histology

• hemorrhage dissecting along lengthwise

• vessel with hemorrhage into the media

Pathogenesis

• clearly related to hypertension

• cystic medial degeneration (CMD)

  • elastic fragmentation of media

  • cystic faces are filled with amorphous proteoglycan material

• CMD is not seen in all cases of dissection and CMD is pretty commonly seen without dissection

Histological stains

• elastic stain: normal aorta: parallel fibers

• elastic stain: cystic medial degeneration: a little degeneration, a little cystic space

• mucin stain: the orifice in the elastic material really lights up

Clinical course

• classically described as abrupt onset of tearing chest pain radiating to the back

• most common cause of death is rupture

• dissection to the aortic root can cause cardiac tamponade, aortic insufficiency, MI

Classification schemes

• Stanford type A and B: ascending aortic involvement vs. descending aortic involvement

• or, Debakey I, II, III; DeBakey I is the most common (60% cases)

• Stanford A (DeBakey I and II) are more common and more dangerous; require surgery

• previously almost uniformly fatal, better now

• require immediate antihypertensives

Category: Medical Subject Notes , Pathology Notes