Peripheral Vascular Disease Flashcards
What is an aneurysm?
What is an arterial dissection?
Aneurysm:
- Localized dilatation of a blood vessel (aorta) or heart
-
Types:
- True: involves all three layers of wall
- False (pseudoaneurysms): Wall defect leading to extravascular hematoma
Arterial dissection:
- blood enters the wall of the artery
What are the two pathologic processes that can cause an aneurysm?
- Inadequate or abnormal syntheses of collagen
or
- Excessive connective tissue degradation
What syndromes are caused by inadequate or abnormal syntheses of collagen?
What is the pathogenesis for each?
-
Marfan syndrome
- Defective synthesis of fibrillin
- Fibrillin is “scaffolding” for deposition of elastic tissue
- Results in cystic medial necrosis of aorta
- Leads to aneurysm formation & aortic dissection
-
Ehlers-Danlos syndrome
- One variant has defective synthesis of Type III collagen
- Leads to aneurysm formation
How can excessive connective tissue degradation lead to anuerysm formation?
- Occurs with increased matrix metalloproteinase (MMP) or decreased tissue inhibitors of metalloproteinase (TIMP)
- In the setting of inflammation (atherosclerosis) polymorphisms of MMP &/or TIMP genes may predispose to aneurysm formation
What can loss of smooth muscle cells lead to in the vascular wall?
-
Loss of smooth muscle cells
- Thickening of intima (due to atherosclerosis)
- Leads to ischemia of inner media
- Systemic hypertension
- **Narrows vasa vasorum **⇒ ischemia of outer media
- Morphologic results is cystic medial degeneration
What are the most common causes of aneurysms?
- Atherosclerosis – abdominal aorta
- Hypertension – ascending aorta
What are some uncommon causes of aneurysms?
- Congenital defects
- Infections (bacteria, fungi)
- Trauma – AV (fistula) aneurysm
- Vasculitis
- Genetic defects in collagen (Marfan’s & Ehlers-Danlos)
- What congenital defects lead to aneurysm formation?
- What infections lead to aneurysm formation?
-
Congenital defects
- Berry aneurysm: bifurcation of cerebral arteries, subarachnoid hemorrhage
-
Infections (bacteria, fungi)
- Mycotic aneurysm: septic emboli, direct extension, direct infection by circulating organisms
- Syphilis (Treponema pallidum)
- What is the most common location of arotic aneuryms?
- What are some less common locations?
- What is the most common etiology of aortic anuerysms?
- What is the most common association of aortic aneurysms?
-
Abdominal aortic aneurysm (AAA): MOST COMMON LOCATION
- Below renal arteries and above bifurcation
- Less common: Arch of aorta, thoracic aorta and iliac arteries
- Most common cause – atherosclerosis
- More common in men & smokers
Describe the **morphology **of aortic aneurysms:
- Up to 15 cm diameter
- Thinning & destruction of media
- Mural thrombus
- Saccular or fusiform
- Variants:
- inflammatory – unknown etiology
- mycotic – secondary infection (salmonella gastroenteritis) of an atherosclerotic wall
What is the classic clinical presentation of AAA?
What complications can arise from AAA?
- More common in men over 50
- Present as pulsatile abdominal mass
Complications:
- Rupture into peritoneum or retroperitoneum
- Vascular obstruction – renal, mesenteric, spinal arteries
- Embolism of atheroma or mural thrombus to kidneys or lower extremities
- Impingement of ureter(s)
Risk of rupture is directly proportional to ____.
size
- Aggressive management for large aneurysms (> 5 cm)
What are causes of thoracic arotic aneurysms?
- Hypertension
- Marfan’s syndrome
- Syphilis (tertiary)
What are clinical features associated with thoracic aortic aneurysms?
-
Mediastinum encroachment
- Tracheal compression
- Esophageal compression
- Bone erosion
- Cough due to irritation of recurrent laryngeal nerve
-
Cardiac Symptoms
- Heart failure due to aortic valve insufficiency
- Aortic rupture
What causes an aortic dissection?
What is the pathogenesis of aortic dissections?
-
Blood between and along laminar planes of media
- Causes a blood-filled channel that easily ruptures
-
Pathogenesis/etiology
-
Hypertension (40-60 years of age):
- > 90% of cases
- Connective tissue abnormality (younger ages): in association with Marfan’s syndrome or Ehlers-Danlos syndrome
- Ascending aorta most commonly involved
- Rare causes:
- post-procedural – arterial cannulation
- pregnancy
-
Hypertension (40-60 years of age):
What is the morphology of aortic dissection?
What patients have a pre-existing condition to aortic dissection?
- Intimal tear within 10 cm of aortic valve
- Dissection plane between middle and outer thirds of wall, in media
- Usually extends anterograde
- Usually ruptures “out”
- May reenter and form a double-barreled lumen
-
In hypertensive patients
- Vasa vasorum: hyaline arteriolosclerosis
- Media: loss of smooth muscle cells
- Pre-existing pathology of cystic medial degeneration in patients with connective tissue disorder (Marfan syndrome)