Aneurysms

Question 1

What is an aneurysm?

Answer 1

Localized abnormal dilation of a blood vessel, or the heart, that may be congenital or acquired

Question 2

What is a TRUE aneurysm?

Answer 2

An intact (but thinned) muscular wall at the site of dilation

Question 3

What is a FALSE aneurysm (pseudo)?

Answer 3

Defect through the wall of the vessel, or heart, communicating with an extravascular hematoma that freely communicates with the intravascular space (“pulsating hematoma”)

Question 4

What is an arterial dissection?

Answer 4

Arises when blood enters a defect in the arterial wall and tunnels b/w its layers

Question 5

When may an aneurysm occur?

Answer 5

An aneurysm may occur whenever the connective tissue of vascular wall is weakened, whether acquired or congenital

Question 6

What can lead to weakening of the connective tissue of the vascular wall?

Answer 6

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

Question 7

What conditions may lead to weakening of the vessel wall by ischemia? Describe where as well.

Answer 7

Atherosclerosis = ischemia of inner media

HTN = ischemia of outer media

Tertiary syphilis = ischemia of outer media (specifically thoracic aorta)

Question 8

How does tertiary syphilis cause ischemia of the outer media?

Answer 8

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)

Question 9

What is cystic medial degeneration?

Answer 9

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

Question 10

What are the 2 most important causes of aortic aneurysms?

Answer 10

Atherosclerosis

HTN

Question 11

How can mycotic aneurysms originate?

Answer 11

Septic emboli - usually complication of infective endocarditis

Extension of an adjacent suppurative (pus-creating) process

Circulating organisms directly infecting the arterial wall

Question 12

What is an abdominal aortic aneurysm (AAA) typically due to?

Answer 12

Atherosclerosis

Question 13

Where does an AAA typically occur?

Answer 13

Abdominal aorta, usually below the renal arteries

Often involves the common iliac arteries

Question 14

In who is an AAA more frequent in?

Answer 14

Men
Smokers
6th Decade of life

Question 15

What are the characteristics of an AAA?

Answer 15

Severe atherosclerosis of the aorta, covered with mural thrombus

May be detected as a PULSATING mass in the abdomen

Question 16

What are some complications of an AAA?

Answer 16

Rupture and hemorrhage
Occlusion of branching arteries & downstream ischemia
Embolism
Impingement on another structure

Question 17

What are lines of Zahn?

Answer 17

Describes a layered thrombus that occurs particularly in the heart/aorta
Alternating layers of platelets and fibrin in the thrombus

Question 18

Rupture risk of an AAA is related to ___.

Answer 18

Aneurysm size

>5 cm usually managed surgically

Question 19

What is a thoracic aortic aneurysm dur to?

Answer 19

HTN

Congenital defect in CT synthesis (Marfan) - less common

Question 20

Describe the general pathogenesis of Marfan syndrome.

Answer 20

Autosomal dominant genetic disorder resulting in defective synthesis of Fibrillin - FBN1 that leads to aberrant TGF-B activity that weakens elastic tissue

Question 21

Clinical presentation of thoracic aortic aneurysm is often due to?

Answer 21

Impingement - Lower respiratory tree, Esophagus, Recurrent laryngeal nerves

Aortic valvular insufficiency

Rupture

Question 22

What is an Aortic dissection? In who does it typically occur in? What is the primary risk factor?

Answer 22

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

Question 23

What is the clinical presentation of Aortic dissection?

Answer 23

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

Question 24

Describe the pathogenesis of Aortic dissection (Be sure to mention location, what happens in HTN pts, etc.)

Answer 24

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

Question 25

What happens if there is a second intimal tear distal to the dissecting hematoma?

Answer 25

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

Question 26

How do you classify dissections? How can you distinguish each? Using what classification?

Answer 26

Type A and B

Type A = involves ascending aorta
Type B do not
Classification using Stanford Classification

Question 27

Which dissection type is more common?

Answer 27

Type A

Associated with high morbidity and mortality

Question 28

What is the most common cause of death for both types of dissections?

Answer 28

Rupture

Dissection may also extend along arterial branches of the aorta, causing potential occlusion of vessels

Question 29

How are Type A dissections managed?

Answer 29

Treated with antihypertensive therapy and an attempt to surgically repair the intimal tear