AV fistula

Question 1

Definition

Answer 1

• Abnormal communication btw artery → vein
  o Bypass capillary network
• Can occur anywhere in vascular system
  o Non cardiac fistulas are uncommon

Question 2

Etiology

Answer 2

• Acquired
  o Blunt penetrating trauma
  o Iatrogenic
  o Neoplastic formation of new vessels
• Congenital

Question 3

Pathophys

Answer 3

• Bypass normal bloodflow
• Shunting from arterial (↑ pressure) → venous (↓ pressure)
  o Initially
   Regional hyper O2 of venous blood
   ↓ peripheral vascular resistance
   ↓ circulation to tissues severed by affected artery
• Collateral circulation maintain perfusion
  o Proliferation of affecting vessels → ↑ # of AV fistulas
   Ectasia
   Arterial venification
   Venous arterialization
• Continuous shunting: venous hypertension + ↑ venous return to heart
  o Volume overload → eccentric hypertrophy
  o ↑ cardiovascular volume → ↑ afterload and HR
  o Can lead to
   ↑ end diastolic volume → L CHF
   High output failure

Question 4

C/s

Answer 4

• Vary depending on location, size, duration, etiology
• Warm, swollen, painful region
• Dermatologic lesions: edema, necrosis, ulceration, pigmentation

Question 5

PE

Answer 5

• Site of fistula
  o Palpable thrill/fremitus
  o Continuous bruit murmur
• Positive Branham sign
  o ↓HR with compression of fistula
• Wide pulse pressure: ↓ diastolic pressure from diastolic runoff

Question 6

Dx

Answer 6

• Angiography for direct visualization of defect

Question 7

Tx

Answer 7

• Surgical ligation
• Coil occlusion