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51 Cards in this Set
- Front
- Back
Is elastin synthesized in the adult aorta?
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NO.
T1/2 = 40 - 70 years .: reduced elastin concentration with aging .: increased prevalence of AAA |
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Components of the Aortic Wall
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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 |
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What is the function of elastin in the Aortic Wall?
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load-bearing protein
Resists AAA formation |
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What is the function of Collagen in the Aortic Wall?
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"safety net"
Resists AAA rupture |
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Degradation of aortic media
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Up-regulation of matrix metalloproteinases (MMPs)
- Relative to inhibitors - MMP-2,-9, and particularly -12 Neutrophil elastase, Plasmin also found in high concentrations |
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What are possible external causes of AAA?
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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" |
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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) |
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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 |
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What are Hazards of Aortic Aneursyms?
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1. Emboli
2. Thrombosis 3. Infection 4. Coagulopathy 5. Fistulae 6. Rupture |
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How big does the dilation of the AAA in order for diagnosis?
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Focal dilatation of an artery involving an increase in diameter of at least 50% as compared the expected normal diameter.
AAA > 3 cm |
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True Aneurysm
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Dilation involving all the vessel wall layers
pulsatile mass that disappears on pressure |
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False Aneurysm
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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. |
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Who gets AAA?
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elderly white males
>50 years with peeak age of 80 years men>women (4-6x more) White> african american |
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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 |
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Diagnosis of AAA rupture based on symptoms
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Most symptomatic AAA
- Rupture - Acute expansion Abdominal or back pain (retroperitoneal hemorrhage) - Can radiate to flank or groin Most are palpable |
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How are most asymptomatic aneurysms detected?
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Ultrasound or CT scan preformed for another reason
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Angiography and AAA
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Not adequate screening tool
- Intraluminal flow channel Contrast administration Invasive Radiation exposure Good surgical planning tool |
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What do you see on X ray with AAA?
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May see a calcium ring around the outside of the AAA
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When is screening for AAA preformed?
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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) |
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What is the risk of rupture for AAA?
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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 |
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What is the effect of Beta blockage on AAA?
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independent predictor of lower expansion rate
(expand less quickly if on beta blocker) |
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When are 6 month interval ultrasound screening recommended for AAA?
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When AAA > 4 cm
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When is surgery preformed on AAA?
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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 |
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What is your life expectancy at 60 years? At 85 years?
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60 years -> 18 more years
85 years -> 5 more years |
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When do you not operate on a patient with AAA?
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when they have a less than 2 year life expectancy
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Factors that contribute to
Observation vs Prophylactic Repair of AAA |
1. Rupture risk
2. Operative risk 3. Patient life expectancy 4. Patient choice |
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What co-morbidities are important to consider before AAA surgery?
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Coronary Artery Disease
Pulmonary Disease Renal Failure |
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Preoperative Assessment for AAA
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Cardiac assessment
- History - Preoperative noninvasive stress testing Pulmonary morbidity - PFT’s - Bronchodilators - Steroids Renal function - Hydration - Evaluation of renal anatomy - Intraoperative maneuvers |
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What do you do to prevent the body from attacking the AAA repair graft?
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wrap it in extra AAA tissue
- prevents aortoenteric fistula |
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Who is a candidate for AAA endograft?
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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. |
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What is the mortality associated with AAA rupture?
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90%
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Aortic Disection
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- 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 |
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Without treatment how soon do you die after an aortic dissection?
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within 2 weeks
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Acute vs. Chronic Aortic Dissection
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Acute
- dx made within 14 days of sxs Chronic - dx made when initial sxs are of greater than 2 wks duration |
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Marfan Syndrome
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- 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. |
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Symptoms of Marfan Syndrome
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dilation of aorta
pectus excavatum arachnodactyly |
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Predisposing Factors for Aortic Dissection
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- 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 |
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Which is an emergency dissection of ascending or descending aorta?
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Ascending aorta
- Mortality 1-3% / hour untreated - Acute aortic regurgitation, rupture, major branch occlusion |
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Manifestations of Aortic Dissection
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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 |
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Aortic Dissection Presentation
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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 |
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Aortic Dissection
DDX |
Acute MI
Thoracoabdominal Aneurysm Pericarditis Pulmonary Embolus Mediastinal Tumors Plueritis Acute Cholecystitis |
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Aortic Dissection Diagnosis
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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 |
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Which Imaging modality is most commonly used with Aortic Dissection?
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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 |
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Ascending Aortic Dissection Treatment
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- Surgical emergency
- Blood pressure control - May require replacement of ascending aorta, aortic valve, and CABG |
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Chronic Descending Aortic Dissection Treatment
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Surgical Indications
- Aneurysmal degeneration > 60 mm - Chronic ischemia secondary stenosis (risk of paraplegia) |
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Acute Descending Aortic Dissection Treatment
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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 |
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What are the most common peripheral aneurysms?
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Femoral (for FALSE) and popliteal (for TRUE)
- Embolize or thrombose –rarely rupture - Frequently associated with other aneurysms. |
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What is the most common visceral aneurysm?
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Splenic artery aneurysm
- Worry about rupture especially in a gravid pt. or an aneurysm > 2-3 cm. |
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Peripheral Artery Aneurysms
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- 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 |
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Lower Extremity Aneurysms
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Prevalence increasing
- Detection - Patient age - Catheter-based interventions Largely Atherosclerotic/degenerative Usually more limb-threatening Profound male predominance (30:1) |
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De Bakey's Classification of Aortic Dissections
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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 |