8/24- Pathology of the Aorta Flashcards
Describe the intima (of the aorta)?
Single layer of endothelial cells, loose CT (GAG) and internal elastic lamina (diffusion of thin intima)
Describe the media (of the aorta)?
How does it receive nutrients?
- Smooth muscle
- Elastic lamellae: // to distribute pressure load
- Collagen: cross-linked: provide strength
Pressure shouldn’t deform!
Gets nutrients from diffusion from lumen through intima
Describe the adventitia (of the aorta)?
Encircles media contains loose CT, nerves, and arteries (vaso vasorum)
What is the number 1 cause of hypertension in kids?
Always secondary; here, in the aorta– due to coarctation
What is a key finding in aortic coarctation?
Rib notching on CXR
- Due to decreased blood flow from posterior intercostals (come straight from aorta; below coarctation) with increased blood flow from anterior intercostals (from subclavian)
- Results in wavy/tortuous arteries that can be see on CXR
What are the different types of aortic coarctation?
- Infantile or pre-ductal
- Adult or post-ductal
What is the treatment for aortic coarctation?
Ressection and end-anastamosis (treat early!)
What is the cause of morbidity/mortality with aortic coarctation?
- HTN
- CHF (L heart failure due to hypertrophy and then R)
- Rupture (increased P in head and neck)
- Endocarditis
Case)
- 24 yo male; 6’4” thin male…
Think Marfan’s!
What causes problems in Marfan’s syndrome?
Defective synthesis of fibrillin -> increased TGF-beta activity and weakening of the elastic tissue -> progressive dilation due to remodeling of the inelastic media
Why is aneurysm and dissection mostly in the ascending aorta in Marfan patients?
Related to LaPlace’s law: WS ~ Pr/2h
What are some congenital diseases that predispose to aneurysm formation:
- Marfan’s syndrome
- Loeys Dietz syndrome
- Ehlers-Danlos syndrome
What is the mechanism behind Loeys-Dietz syndrome?
Mutations in TGF-beta cause abnormal elastin and collagen I and III
What is the mechanism behind Ehlers-Danlos syndrome?
Defective type III collagen
What are some acquired aortic disease and age-related changes?
- Decrease in elastic fiber: dilatation and aneurysms
- Atherosclerosis:AA aneurysms
- ?
Aortic root dilatation causes what?
Aortic valve incompetence (insufficiency?)
T/F: unfolding of the aorta is a change associated with aging?
True
- Aorta straightens out
- Increased length of descending aorta
- (Must be distinguished from aortic aneurysm)
T/F: atherosclerosis is a change associated with aging?
True
- In the elderly, atherosclerosis is more often irreversible (in middle age there was more adaptive thickening; reversible)
Pathophysiology of atherosclerosis?
Shear stress -> thickening -> high BP -> shear stress…
What is xanthoma?
Cholesterol deposition in intima (part of the atherosclerosis process)
Case)
- 54 yo Af AM male presents to ER with acute onset of abdominal and low back pain
- PMH: DMII, HTN, Hypercholesteremia
- …. Dx? What are his risk factors?
Dx: rupture abdominal aortic aneurysm
- Pic here is “fusiform aneurysm”- circumferential dilatation
Risk factors:
- DM -> poor nourishment -> wall weakness
- HTN
- Hypercholesteremia, DM, and obesity are all implicated in development of atherosclerosis
Different types of aneurysm?
True aneurysm
- Saccular
- Fusiform
False aneurysm: extravascular CT; hematoma with extravasation of blood
Dissection: tear in intima with extravasation of blood
Pathogenesis of aneurysms?
- Arterial ECM is in continual remodeling; balanced synthesis and degradation
- Increased degradation vs. synthesis (with age) through: apoptosis, proteolytic enzymes, and matrix metalloproteinase (MMP) degrade the ECM
- Ischemia: loss of SM and increase in GAGs
What are the 2 most common disorders that predispose to aortic aneurysms?
- Atherosclerosis
- Hypertension
T/F: Aortic aneurysms occur most commonly in the abdomen?
True
- Atherosclerosis is commonly most severe at the distal aorta
- Results in atherosclerotic abdominal aneurysms
- Also have fewer vaso vasorum here
What are conditions that weaken vessel walls resulting in aneurysms?
- Diabetes mellitus
- Trauma
- Vasculitis
- Congenital defects (e.g. berry aneurysms)
- Infections (mycotic aneurysms)
What may cause thoracic aortic aneurysms?
Tertiary syphilis
- Obliterative endoarteritis
- Predeliction for small vessels
- Involvement of vasa vasorum of aorta can -> aneurysmal dilation
What is the most likely COD in pt with abdominal aortic aneurysm, HTN, DMII..?
Rupture of aortic aneurysm
Clinical Outcomes of AAAs?
- Rupture (into peritoneal or retroperitoneal cavity) with potentially fatal hemorrhage
- Obstruction of vessel -> ischemic injury (iliac, renal, mesenteric, vertebral branches)
- Impingement of adjacent structures (ureter, erosion of vertebrae)
- Embolism from atheroma or mural thrombus
T/F: mycotic AAAs are due to systemic fungal infections?
False
- Mycotic AAAs are atherosclerotic aneurysms that have become infected by circulating organisms which may be fungal but are more commonly due to bacteremia (e.g. Salmonella gastroenteritis)
How might a pt present with thoracic aortic aneurysms?
- Encroachment of mediastinal structures
- Respiratory difficulties
- Difficulty swallowing
- Bone pain from erosion of ribs or vertebra
- Aortic valve dilation with resulting valvular insufficiency
- Narrowing of coronary ostia – ischemia
- Rupture
What factor is directly associated with increased risk of rupture?
Risk of rupture is directly related to size
- LaPlace’s law: WS ~ diam and internal P
- Blood pressure is the most important factor affecting increase in size (increases WS directly and indirectly through gradual increase in size)
Best treatment for thoracic aortic aneurysm?
Surgery is not better than management unless you have impending aneurysm
Case)
- 60 yo woman presents to ED with acute onset, severe ripping upper back pain
- PMH: HTN
- HR: 100
- BP: 210/105
- SpO2: 100% RA
What is this?
Risk factors (general, not just hers)?
Dx: Aortic dissection
- Dissection of blood between laminar planes of the media
- Formation of channel within aortic wall
- Can rupture outward resulting in massive hemorrhage
Risk factors:
- Age
- HTN
- Sex
What is seen here?
Aortic dissection
- Blood-filled channel within the aortic wall
Epidemiology of aortic dissection?
> 90% of pts with dissection are men 40-60 yo with hx of HTN
- Minority are younger with CT disorders
Describe the gross findings in this picture?
Hemocardium
- Consequence of (ascending) thoracic aortic dissection with retrograde channeling of blood into the heart
- Can lead to cardiac tamponade
Risk of complications in aortic dissection depend on what?
Difference between classes?
Level of aorta affected
- (DeBakey I-III)
- Type A: treated surgically; pressure could impinge on coronary arteries -> ischemia and valve dysfunction; very symptomatic
- Type B: treated medically
What are some consequences of retrograde dissection of the aorta?
- Aortic valvulopathy
- Cardiac tamponade
- Myocardial infarction (due to decreased perfusion)
- Extension into great arteries of the neck
- Compression of adjacent vessel
What is the most common false aneurysm (pseudoaneurysm)?
Post MI rupture
- Contained by pericardial adhesion or at the junction of a vascular graft with a natural artery (anastomosis)
Case)
- 54 yo white male with abdominal pulsatile mass had bilateral hydronephrosis
Diagnosis?
AAA may impinge on the ureters as they pass into the pelvic cavity to attach to the bladder
Describe the gross findings?
Thoracic aortic dissection
- Dissection area is black -> blood clot within the wall of thoracic aorta
What is an acquired connective tissue disorder that may dispose to aneurysms and thus dissections?
Vitamin C deficiency
- Scurvy
- Defective collagen cross-linking
- Results in aneurysm formation (cystic medial degeneration)
What is the cause of morbidity/mortality with aortic coarctation?
- HTN
- CHF
- Rupture
- Endocarditis
What is an anuerysm? Classifications/causes?
A localized abnormal dilation
- Congenital
- Acquired
True aneurysm:
- Atherosclerotic
- Syphilitic
- Congenital aneurysm
- Ventricular aneurysm
False aneurysm (pseudo-aneurysm)
