Abdominal Aortic Aneurysm

Question 1

Aneurysm

Answer 1

permanent dilatation of an artery with an increase in diameter greater than 50% (1.5 times its normal diameter)

Question 2

Where are the more common aneurysms found? Where else do they CO-occur

Answer 2

Aneurysms of the infrarenal Aorta are by far the most common arterial Aneurysms encountered They occur 3-7 times more frequently than Thoracic Aneurysms Other Aneurysms frequently coexist in patients with AAA: Iliac Aneurysms ~ 20-30% Femoropopliteal Aneurysms ~ 15%

Question 3

What is the relevance of popliteal aneurysms?

Answer 3

 Conversely, Popliteal Aneurysms are markers of AAA  AAA can be found in 8-35% of patients with a unilateral popliteal aneurysm  but up to 50% of patients who have bilateral popliteal Aneurysms  It is considered malpractice not to look for AAA’s when other Aneurysms are found!

Question 4

Cause and pathogenesis of aaa

Answer 4

1.90% are associated with atherosclerosis. It is considered a facilitating process. 2.Increased ratio of collagen to elastin in the walls 3.Elastin fragmentation, loss of smooth muscle causes elongation and tortuousness 4.Inflammation (increased C-Reactive Protein and Cytokines) 5.Latent infectious process (chlamydia pneumoniae or oral flora) 6.Deficiencies in antiproteases (such as alpha-1 antitrypsin – higher risk of rupture in Emphysema patients) 7.Uncommon causes include Cystic Medial Necrosis, Ehlers-Danlos Syndrome, and Syphilis.

Question 5

Laplace’s Law

Answer 5

This law describes the relationship among the  tangential stress (T) tending to disrupt the wall of a sphere,  the radius (R) and  the transmural pressure (P): • T=PR

Question 6

Clinical manifestations

Answer 6

1.70-75% of all AAA’s are Asymptomatic. 2.Most are found: a) On routine physical exam – pulsatile mass with a bruit b) Imaging performed for another pathology c) Unrelated abdominal operation 3.Back pain – Aorta is retroperitoneal 4.Flank pain 5.Abdominal Pain – compression of intestines most commonly the duodenum 6.Abrupt onset of pain – 10/10 is characteristic of Aneurysmal rupture 7.Ruptured AAA’s make up ~25% of Aneurysm findings 8.Majority of Ruptures occur posterior-lateral on the left side of the Aorta 9.Aortocaval fistula or Aortoenteric fistula may occur 10.Classic clinical presentation of ruptured AAA is pain (back, flank, abdomen), hypotension – shock, palpable pulsatile abdominal mass

Question 7

Diagnostic Methods

Answer 7

Careful Physical Exam X-rays Ultrasound Cat Scan MRI Aortography

Question 8

Physical Exam

Answer 8

• AAA needs to be ~ 5 cm in diameter to be detected in a thin person. • Rarely palpable in obese patients. • Palpable Mass, Abdominal Bruit

Question 9

X-rays

Answer 9

Plain abdominal and lateral spine radiographs can establish the diagnosis (67-75% ) of AAA’s by detecting a fine rim of calcium in the Aortic wall. However, it is not accurate in determining maximum size

Question 10

Ultrasound

Answer 10

• No Radiation • Accurate. Able to measure in three dimensions • Sensitivity 100%, • specificity 95-99% • Not good for suprarenal or Thoracic Aneurysms • Not accurate in demonstrating rupture • Bowel gas, barium, and obesity can impair accuracy, especially in visualizing the iliac arteries. • Best option for continued surveillance

Question 11

Cat Scan

Answer 11

• Radiation. • Spiral or Helical CT allows visualization from any angle • Slices are usually 2 to 3 mm. • Using contrast (CTA: Cat Scan angiogram) gives accurate “Road Mapping” and identifies other arteries that may need repair as well. • Contrast is Nephro-toxic

Question 12

MRI

Answer 12

• Lack of Ionizing Radiation, use of non-nephrotoxic contrast (gadolinium) • Better at visualizing branch vessels, especially the renal arteries • May be five (5) times more expensive than CT

Question 13

Aortography

Answer 13

• “Gold Standard”, but rarely used by me because CTA is essentially non-invasive • It requires arterial access which could lead to dissection, embolization, or pseudoaneurysm. • Large contrast load and longer radiation exposure • Recommended for the following indications: a) Visceral ischemia b) Occlusive ilio-femora vascular lesions c) Occlusive pop-tibial vascular lesions d) Severe hypertension thought to be caused by renal artery stenosis e) Suspicion of Horseshoe Kidney f) Presence of femoral and / or popliteal aneurysms

Question 14

Ultrasound- Repeat Testing

Answer 14

•If AAA is less than 4.5 and patient is asymptomatic • Repeat Ultrasound in six months, • If unchanged, then repeat in one year. •If AAA is greater than 4.5 cm, repeat Ultrasound every six months

Question 15

Indications for Surgery

Answer 15

If symptomatic  AAA is 5.0 cm in diameter  Increase in any size Aneurysm by 1 cm in one year’s time

Question 16

Risk of Rupture

Answer 16

 AAA’s less than 4.5 cm less than 9% / 5 years  5.0 cm AAA’s: 33-35% / 5 years  6.0 cm AAA’s: 6.6% / 1 year, 50% / 5 years  7.0 cm AAA’s : 19% / 1 year, 95% / 5 years  > 7.5 cm – 100% Rupture / 5 years •Once ruptured mortality is 100%

Question 17

Treatment AAA

Answer 17

No medical management at this time Surgery (3 approaches) Endovascular Repair

Question 18

Medical Management

Answer 18

There is no medical treatment for cure. To decrease risk of rupture: 1. Control Blood Pressure 2. No Heavy Lifting or Strenuous Activity 3. Stop Smoking 4. Ambulation 5. Platelet Inhibition

Question 19

Surgery

Answer 19

Open/Three (3) approaches: 1. Full length midline (“stem to stern”), 2. Wide transverse 3. Oblique (Retroperitoneum) • Graft material is either Polyester (Dacron) knitted or woven, or Polytetrafluorethylene (PTFE) (Gortex) “Teflon” • Sew Aneurysm Sac over graft to prevent Aortoenteric Fistula

Question 20

Endovascular Repair:

Answer 20

1. Must have access through femoral and iliac arteries 2. Must have landing zone below renal arteries 3. Must maintain at least one internal iliac artery (Hypogastric Artery) 4. Risk of Dissection, Rupture during surgery

Question 21

PreOp

Answer 21

1. Cardiac evaluation, probable stress test 2. Pulmonary Function test 3. Type and Screen (possible type + cross) (will use cell saver)

Question 22

After open or endovascular repair

Answer 22

Interrogate repairs with Cat Scan at: 1. 1 month, 2. 6 months, 3. 1 year and 4. then yearly Endovascular repairs at this time need to be checked indefinitely

Question 23

4 Types of Endovascular Leaks

Answer 23