Aneurysms Flashcards
What is an aneurysm?
Localized abnormal dilation of a blood vessel, or the heart, that may be congenital or acquired
What is a TRUE aneurysm?
An intact (but thinned) muscular wall at the site of dilation
What is a FALSE aneurysm (pseudo)?
Defect through the wall of the vessel, or heart, communicating with an extravascular hematoma that freely communicates with the intravascular space (“pulsating hematoma”)
What is an arterial dissection?
Arises when blood enters a defect in the arterial wall and tunnels b/w its layers
When may an aneurysm occur?
An aneurysm may occur whenever the connective tissue of vascular wall is weakened, whether acquired or congenital
What can lead to weakening of the connective tissue of the vascular wall?
Defective vascular wall CT:
- Marfan syndrome (defective fibrillin synthesis)
- Ehlers-Danlos
- Scurvy
Net degradation of vascular CT
-Inflammatory conditions (such as atherosclerosis) - increase in matrix metalloproteases
Weakening of vessel wall by ischemia
What conditions may lead to weakening of the vessel wall by ischemia? Describe where as well.
Atherosclerosis = ischemia of inner media
HTN = ischemia of outer media
Tertiary syphilis = ischemia of outer media (specifically thoracic aorta)
How does tertiary syphilis cause ischemia of the outer media?
Obliterative endarteritis (characteristic of late-stage syphilis) shows a predilection for small vessels, including those of vasa vasorum of thoracic aorta
Leads to ischemic injury of the aortic media and aneurysmal dilation, which sometimes involves the aortic valve annulus (aortic valve regurgitation)
What is cystic medial degeneration?
Disrupted and disorganized elastin filaments and increased ground substance (proteoglycans)
An affect of loss of vascular wall elastic tissue, or ineffective elastin synthesis
Final common result of different conditions, including ischemic medial damage and Marfan Syndrome
What are the 2 most important causes of aortic aneurysms?
Atherosclerosis
HTN
How can mycotic aneurysms originate?
Septic emboli - usually complication of infective endocarditis
Extension of an adjacent suppurative (pus-creating) process
Circulating organisms directly infecting the arterial wall
What is an abdominal aortic aneurysm (AAA) typically due to?
Atherosclerosis
Where does an AAA typically occur?
Abdominal aorta, usually below the renal arteries
Often involves the common iliac arteries
In who is an AAA more frequent in?
Men
Smokers
6th Decade of life
What are the characteristics of an AAA?
Severe atherosclerosis of the aorta, covered with mural thrombus
May be detected as a PULSATING mass in the abdomen
What are some complications of an AAA?
Rupture and hemorrhage
Occlusion of branching arteries & downstream ischemia
Embolism
Impingement on another structure
What are lines of Zahn?
Describes a layered thrombus that occurs particularly in the heart/aorta
Alternating layers of platelets and fibrin in the thrombus
Rupture risk of an AAA is related to ___.
Aneurysm size
>5 cm usually managed surgically
What is a thoracic aortic aneurysm dur to?
HTN
Congenital defect in CT synthesis (Marfan) - less common
Describe the general pathogenesis of Marfan syndrome.
Autosomal dominant genetic disorder resulting in defective synthesis of Fibrillin - FBN1 that leads to aberrant TGF-B activity that weakens elastic tissue
Clinical presentation of thoracic aortic aneurysm is often due to?
Impingement - Lower respiratory tree, Esophagus, Recurrent laryngeal nerves
Aortic valvular insufficiency
Rupture
What is an Aortic dissection? In who does it typically occur in? What is the primary risk factor?
Occurs when blood enters defect in the intima and travels through tissue plane within layers of the aortis media
Typically occurs in Hypertensive males (40-60) and younger patients with disorders of vessel CT (Marfan)
Primary risk factory = HTN
What is the clinical presentation of Aortic dissection?
Sudden onset of severe chest pain (usually beginning in anterior chest), radiating to the back b/w the scapulae and moving downwards as the dissection progresses
Can be confused with AMI
Describe the pathogenesis of Aortic dissection (Be sure to mention location, what happens in HTN pts, etc.)
Blood enters aortic wall via an intimal tear forming an intramural hematoma
Most arise in ascending aorta, within 10 cm of aortic valve (b/c of highest pressure)
Dissections can rupture through adventitia –> massive hemorrhage (into thoracic and abd cavities) or Cardiac Tamponade (hemorrhage into pericardial sac)
Usually in HTN pts, some degree of cystic medial degeneration
What happens if there is a second intimal tear distal to the dissecting hematoma?
The hematoma reenters the lumen of the aorta through a second distal intimal tear, a new false vascular channel (“double-barreled aorta”) is created
This averts a fatal extra-aortic hemorrhage, and over time, such false channels can be endothelialized to become recognizable chronic dissections
How do you classify dissections? How can you distinguish each? Using what classification?
Type A and B
Type A = involves ascending aorta
Type B do not
Classification using Stanford Classification
Which dissection type is more common?
Type A
Associated with high morbidity and mortality
What is the most common cause of death for both types of dissections?
Rupture
Dissection may also extend along arterial branches of the aorta, causing potential occlusion of vessels
How are Type A dissections managed?
Treated with antihypertensive therapy and an attempt to surgically repair the intimal tear
