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51 Cards in this Set

  • Front
  • Back
Is elastin synthesized in the adult aorta?
NO.

T1/2 = 40 - 70 years

.: reduced elastin concentration with aging
.: increased prevalence of AAA
Components of the Aortic Wall
Smooth muscle

Matrix proteins
- Elastin
- Collagen

Decreasing matrix concentrations from proximal to distal aorta
- 58% decrease in elastin between supra and infrarenal aorta

- Absent vasa vasorum in AAA below renals
What is the function of elastin in the Aortic Wall?
load-bearing protein

Resists AAA formation
What is the function of Collagen in the Aortic Wall?
"safety net"

Resists AAA rupture
Degradation of aortic media
Up-regulation of matrix metalloproteinases (MMPs)
- Relative to inhibitors
- MMP-2,-9, and particularly -12

Neutrophil elastase, Plasmin also found in high concentrations
What are possible external causes of AAA?
Chronic adventitial and medial infiltrate
- May be related to Chlamydia pneumoniae infection

Aortic aneurysm antigenic protein (AAAP-40)
- Collagen associated microfibril/glycoprotein
- Highest concentrations in abdominal aorta
- Shares amino acid sequence with
>Treponema pallidum
>CMV
- Possibility of autoimmune reaction
>"Molecular mimicry"
Is there a Genetic component
to AAA?
- Numerous studies noting familial clustering of AAA

-15-20% family history

- Single dominant gene with low penetrance (Majumder/Verloes)

- Susceptibility alleles for AAA involving the DRB1 major histocompatibility locus (Tilson)
Complex Pathogenesis of AAA
(All the major groups that could cause it)
1. Loss of elastin/collagen
2. Up-regulation of MMPs
3. Infectious component
4. Inflammatory response
5. Genetic component
What are Hazards of Aortic Aneursyms?
1. Emboli
2. Thrombosis
3. Infection
4. Coagulopathy
5. Fistulae
6. Rupture
How big does the dilation of the AAA in order for diagnosis?
Focal dilatation of an artery involving an increase in diameter of at least 50% as compared the expected normal diameter.

AAA > 3 cm
True Aneurysm
Dilation involving all the vessel wall layers

pulsatile mass that disappears on pressure
False Aneurysm
pulsitle mass that involves none of the vessel wall layers.

it is the result of a punctured artery (i.e. cardiac cath), surrounded with fibrosis.

must be repaired.
Who gets AAA?
elderly white males
>50 years with peeak age of 80 years

men>women (4-6x more)

White> african american
AAA
Presentation
- Most AAAs asymptomatic
- described as abdominal pulsation or palpable pulsatile mass

Detection with PE:
dependent on AAA size, skill of examiner, focus of the exam, obesity of patient
Diagnosis of AAA rupture based on symptoms
Most symptomatic AAA
- Rupture
- Acute expansion

Abdominal or back pain (retroperitoneal hemorrhage)
- Can radiate to flank or groin

Most are palpable
How are most asymptomatic aneurysms detected?
Ultrasound or CT scan preformed for another reason
Angiography and AAA
Not adequate screening tool
- Intraluminal flow channel

Contrast administration

Invasive

Radiation exposure

Good surgical planning tool
What do you see on X ray with AAA?
May see a calcium ring around the outside of the AAA
When is screening for AAA preformed?
preformed by Ultrasound in US in men 65-75 years who have ever smoked

- Males
- > 65 years of age
- Smokers
- Family history
- Unreliable exam (esp. if obese)
What is the risk of rupture for AAA?
Rupture occurs when intraluminal forces overwhelm the burst strength of the aorta
- greater with rapidly expanding and larger AAA
Simplistic approach
- Law of Laplace: Tension = radius x pressure
- But AAA not perfect cylinder
- Wall thickness of variable strength
What is the effect of Beta blockage on AAA?
independent predictor of lower expansion rate

(expand less quickly if on beta blocker)
When are 6 month interval ultrasound screening recommended for AAA?
When AAA > 4 cm
When is surgery preformed on AAA?
When the risk of rupture is higher than the risk of repair

- 5.5 cm is the surgical cut off size
- smoking and COPD increase rupture risk independent of size
- women may qualify earlier
What is your life expectancy at 60 years? At 85 years?
60 years -> 18 more years

85 years -> 5 more years
When do you not operate on a patient with AAA?
when they have a less than 2 year life expectancy
Factors that contribute to
Observation vs Prophylactic Repair
of AAA
1. Rupture risk
2. Operative risk
3. Patient life expectancy
4. Patient choice
What co-morbidities are important to consider before AAA surgery?
Coronary Artery Disease

Pulmonary Disease

Renal Failure
Preoperative Assessment for AAA
Cardiac assessment
- History
- Preoperative noninvasive stress testing

Pulmonary morbidity
- PFT’s
- Bronchodilators
- Steroids

Renal function
- Hydration
- Evaluation of renal anatomy
- Intraoperative maneuvers
What do you do to prevent the body from attacking the AAA repair graft?
wrap it in extra AAA tissue

- prevents aortoenteric fistula
Who is a candidate for AAA endograft?
need to have 15 mm above the aneurysm and below renals... must have ileal arteries that can accept graft

- Patients with an AAA warranting surgical repair.
- Patients who can tolerate a surgical procedure.
- Patients who can await/tolerate extensive imaging studies.
- Patients who are generally poor candidates for open repair.
- Patients who are committed to long-term follow-up.
What is the mortality associated with AAA rupture?
90%
Aortic Disection
- Characterized by separation of the aortic wall layers by extra luminal blood that usually enters the aortic wall through an intimal tear
- Blood may circulate between the normal aortic lumen (True Lumen) and the abnormal channel (False Lumen)
- Septum separates lumens
- Multiple re-entry sites
Without treatment how soon do you die after an aortic dissection?
within 2 weeks
Acute vs. Chronic Aortic Dissection
Acute
- dx made within 14 days of sxs

Chronic
- dx made when initial sxs are of greater than 2 wks duration
Marfan Syndrome
- Hereditary Connective tissue disorder: Autosomal dominant- variable penetrance –Defect in fibrillin-1

- Incidence 1/5-10,000

- Affects Skeleton, heart, major vessels, lungs, eyes, etc.
Symptoms of Marfan Syndrome
dilation of aorta

pectus excavatum

arachnodactyly
Predisposing Factors for Aortic Dissection
- Male : Female 2:1 – 5:1
- Location
>Ascending – Age 50 – 55 years
> Descending (after subclavian)– Age 65 – 70
- Chronic systemic hypertension
- Aortic Diseases
>Marfan, Coarctation, Ehlers-Danlos
- Bicuspid Aortic Valve
- Trauma
>Cannulation, interventional procedures
- Cocaine
- Rebound from abrupt discontinuation of B-Blocker therapy
- Pregnancy
>Women < 40 yrs. - 50% of dissections occur during pregnancy
Which is an emergency dissection of ascending or descending aorta?
Ascending aorta
- Mortality 1-3% / hour untreated
- Acute aortic regurgitation, rupture, major branch occlusion
Manifestations of Aortic Dissection
Acute aortic regurgitation
- Diastolic murmur

Shock
- Pericardial tamponade
- Coronary artery compression with MI
- Rupture

Obstruction of branch arteries
- Stroke / Spinal cord ischemia
- Renal failure
- Pulse Deficit
Aortic Dissection Presentation
Pain (95%)
- Sharp, ripping, tearing
- Abruptness is most specific characteristic
- Usually does not radiate to neck, shoulder, or arm as in acute coronary syndrome
- Location may reflect distribution of dissection

Hypertensive
Aortic Dissection
DDX
Acute MI
Thoracoabdominal Aneurysm
Pericarditis
Pulmonary Embolus
Mediastinal Tumors
Plueritis
Acute Cholecystitis
Aortic Dissection Diagnosis
Clinical suspicion
- History and PE

Ascending / Descending

CXR
- Widening of mediastinal shadow

EKG
- Nonspecific changes
- Rule out Acute Coronary Syndrome

Imaging Techniques
- CT, MRI, TEE, Angiography
- All have supportive studies identifying high sensitivity, specificity, PPF, NPF
- Hospital dependent
Which Imaging modality is most commonly used with Aortic Dissection?
Computed Tomography Scanning
Most commonly used
Identify true and false lumen and branch vessel perfusion
Contrast
Difficult to identify site of tear and valve involvement
Ascending Aortic Dissection Treatment
- Surgical emergency

- Blood pressure control

- May require replacement of ascending aorta, aortic valve, and CABG
Chronic Descending Aortic Dissection Treatment
Surgical Indications
- Aneurysmal degeneration > 60 mm
- Chronic ischemia secondary stenosis (risk of paraplegia)
Acute Descending Aortic Dissection Treatment
Medical Treatment
- Aggressive blood pressure control with B-Blockers and nitroprusside
- A-line, ICU, CV access
- Monitor for signs of progression or end-organ ischemia
- Long-term aggressive blood pressure control and risk factor modification
What are the most common peripheral aneurysms?
Femoral (for FALSE) and popliteal (for TRUE)
- Embolize or thrombose –rarely rupture
- Frequently associated with other aneurysms.
What is the most common visceral aneurysm?
Splenic artery aneurysm
- Worry about rupture especially in a gravid pt. or an aneurysm > 2-3 cm.
Peripheral Artery Aneurysms
- Much more likely to embolize or thrombose than to rupture
- Frequently bilateral and associated with other aneurysms including AAA’s
- Popliteal aneurysms are the most common atherosclerotic peripheral aneurysm
- Femoral aneurysms are more common if “false aneurysms” are included
Lower Extremity Aneurysms
Prevalence increasing
- Detection
- Patient age
- Catheter-based interventions

Largely Atherosclerotic/degenerative

Usually more limb-threatening

Profound male predominance (30:1)
De Bakey's Classification of Aortic Dissections
Based on where it starts and how far it continues:

Type 1- at aortic valve and continues through descending aorta

Type 2 – start at aortic valve and stops at aortic arch

Type 3 – distal or descending aorta only