Aortic Dissection and Aneurysm - Pathoma


DISSECTION
  • Blood vessel wall
    • Intima
    • Media
    • Adventitia
  • Blood gets through intima, rips across media, dissecting the wall
  • Mostly occurs in proximal 10cm of aorta
    • As right beside heart where pressure is highest
    • Also, wall is very thick here, so diffusion of O2 across wall is not enough to meet all transmural demands
    • So have vasa vasorum ("vessels of the vessels") in adventitia to supply O2 from outside, in
  • When there's pre-existing weakness of media
    • Most common cause = HTN
      • Causes hyaline arteriosclerosis of vasa vasorum
      • Dec blood/O2 supply to deep parts of wall
      • Causing cell death and wall weakening
    • Also assoc with inherited connective tissue disorders
      • Media contains lots of elastic tissue
      • So eg Marfan's syndrome - fibrilin defect [FBN1, molecule that elastin laid down on]  
        • get cystic medial degeneration
          • (which can also be a separate AD hereditary condition: cystic medial necrosis)
        • nb also mitral and aortic valve prolapse etc
      • and Ehlers Danlos - defective collagen [COL3A1 etc, Tenascin-X, PLOD1, ADAMTS2]
  • Presents
    • Sharp tearing chest pain
    • Radiates to back
  • Complication
    • Pericardial tamponade
      • Most common cause of death
      • if dissects back to pericardium
    • Obstruction of renal arteries
      • if extends down to renal arteries
      • causing ischaemia
    • Rupture
ANEURYSMS

Thoracic aneurysm
  • Balloon like dilatation of thoracic aorta
  • Must be weakness in wall
  • Causes
    • Tertiary syphilis
      • End-arteritis
      • Inflammation of small blood vessels
      • inc of vasa vasorum
      • So atrophy of aortic wall and weakening
      • Tree-bark appearance
        • due to Fibrosis
    • Marfan's
    • TB
    • Ehlers Danlos
    • Loeys-Dietz syndrome
    • Aortitis inc Behçet's disease
  • Complications
    • Dilatation of aortic root
      • Pull on root of aortic valve
      • Causes aortic insufficiency
    • Compression of mediastinal structures
    • Thrombosis, embolism
      • Flow turbulent as no longer a nice straight tube
      • Can get thrombosis along dilated walls of aneurysm
    • Dissection
  • Most aSx
    • Unless complications
AAA
  • Occurs below renal arteries
    •     very rarely higher
  • Above aortic bifurcation to the common iliacs
  • Weakening due to atherosclerosis
    • Men
    • Smokers
    • >60 old
    • HTN
    • One of most common areas for this
  • Presents
    • Outwardly pulsatile abdominal mass
    • Grows with time till POP!
  • Risk of rupture esp when >5cm
    • Triad of presentation:
      • Hypotension
      • Pulsatile abdo mass - blood flying out!
      • Flank pain - blood is irritant
      • also back pain
Robbins Basic Pathology, Robbins Pathologic Basis of Disease, Robbins Review of Pathology (MCQs - very path-y), Robbins Flash Cards, Baby Robbins, Robbins Atlas - some exact same images come up in the exam, 100 Cases in ClinicalPathology - possibly the best Qbank for the practical