Abdominal Aortic Aneurysms
Elizabeth Pensler, DO
Vascular Surgery
Kansas City Review April 3-5th 2014
Definition of Aneurysm
• Focal and persistent dilatation of the diameter
of an artery of 150% or more
• Transverse diameter of 3 cm or greater
• Normal aortic
diameter gradually
decreases from the
thorax (28 mm in
men) to the
infrarenal location
(20 mm in men)
Types of Aneurysms
• True vs. False (pseudoaneurysm)
– True: involves all 3 layers of the arterial wall
– False: Presence of blood flow outside of
normal layers of arterial wall. Wall of false
aneurysm is compose of the compressed,
surrounding tissues.
Types of Aneurysms
Etiology
• Degenerative
•
•
•
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Incorrectly termed atherosclerotic
Not typically assoc. with occlusive disease
Complex degenerative process
Calcification and atherosclerotic
pathology present
• Inflammatory
• Triad ab or back pain, pulsatile (+/- tender)
abdominal mass, elevate ESR
• Dx made - periaortic inflammatory rind on CT
– Post-dissection- up to 20% of
aneurysms are related to previous
dissection. Overtime, develops into true
aneurysm
– Traumatic
– Developmental Anomalies- persistent
sciatic arteries, aberrant right subclavian
artery
– Infectious- Can be primary or secondary
infections.
– Congenital- Tuberous sclerosis, aortic
coarctation, Marfan’s.
Crawford Aneurysm Type
Epidemiology
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15,000 Deaths per year USA
13th leading cause of death in USA
1.8-6.6% of patients in Autopsy series!
Strong male predominance 3:1 - 8:1
Racial distribution Whites > Blacks
Increasing Incidence of AAA
• Inc. 2.6X from 2.62 deaths per 100,000
in 1981 to 6.82 per 100,000 in 2000
• Hospital admissions rose 3X
• Increases in both elective admissions
(from 3.05 to 7.80 per 100 000) and
emergency admissions (from 7.44 to
11.23 per 100 000)
•
Br J Surg 2003 Dec;90(12):1510-5 Best VA; Price JF; Fowkes FG
Genetic predisposition
• 15-20% have 1st degree relative with AAA
• 11.6x more common in persons 1st degree
• Duplex 25% males and 7% females have
AAA if 1st degree relative has AAA
• 69% risk of AAA in offspring of women
with AAA!
• Females rise from 14% to 35% in affected
families
AAA: Associated conditions
• Emphysema: Strongest independent risk factor
for rupture of a known AAA
– Destruction elastin matrix in lung and aortic
wall may have a common cause (e.g. alpha 1
antitrypsin deficiency)
Range of Potential Rupture Rates for a
Given Size of Abdominal Aortic Aneurysm
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AAA Diameter (cm) Rupture Risk (%/yr)
<4
0
4-5
0.5-5
5-6
3-15
6-7
10-20
7-8
20-40
>8
30-50
Operative Mortality of AAA Repair
• 3 – 5% for open repair
• 1% for EVAR
Assessing the AAA patient
•
•
•
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Normal - aorta 1-2.4cm & iliac 0.6-1.2cm
Aneurysm - Aorta >3cm & iliac > 2cm
Average expansion rate approximately 0.33 cm per year.
Risk Factors for aneurysm
– Older age, male gender, white race, positive family history,
smoking, HTN, hypercholesterolemia, PVD, CAD.
• Ultrasound
– used to diagnose and monitor AAA until aneurysm
approaches size at which repair considered.
• Computed Tomography
– used in preop assessment of AAA.
Ruptured AAA
• No significant overall change in mortality with
open repair from 1991-2006
• Overall mortality for ruptured AAA = 90%
– Mortality rate for patients who arrive at hosptial alive =
40-70%
• High postop mortality rate due to MI, renal
failure, and multi-organ failure
– Ischemia-reperfusion injury, hemorrhagic shock, lower
torso ischemia
• rEVAR significantly reduces mortality of ruptured
AAA patients (31 vs 50%)
Screening for AAA
• US Preventive Services Task Force
– Men 65-75 yo who have ever smoked
– Not for or against men 65-75yo who never smoked
– Does not recommend screening for women
• Society of Vascular Surgery, Medicare
Screening
– Men smoked at least 100 cigarettes during their life
– men and women with a family history of AAA
• Only screen patients candidates for repair.
Choosing between Surgery &
Observation
1.
2.
3.
4.
Risk for AAA rupture without surgery
Operative risk of repair
Patient’s life expectancy
Personal preferance of patient
1. Risk of Rupture
• Size matters:
– Aneurysm > 5cm 6-16%
– > 7cm 33% annual rupture rate
• Wall stress analysis
• Saccular aneurysm have higher rate of
rupture
• HTN, COPD, active smoking independent
predictors of rupture
• (+) family hx tend to rupture
• Expansion rate
2. Operative Risk of Repair
• Mortality after:
– elective open AAA ~ 5%
– EVAR 1%
• 6 independent RF’s for mortality Open
repair
– Creatinine > 1.8, CHF, EKG detected
ischemia, Pulmonary dysfunction, older
age, female gender.
• Cardiac, pulmonary, renal, and GI risks
with each proceudre.
3. Patient’s Life Expectancy
• Very difficult to assess due to patient’s comorbidities
• Typical 60yo surviving AAA repair has
13year life-expectacy
• 70yo has 10year life-expectancy
• 80 yo has 6 year life-expectancy.
4. Personal Preference of Patient
• Fear of AAA vs. Fear of surgery
• Anecdotal experiences of friends and
family
• Procedures provided in community by
interventional specialists and surgeons.
Medical Management of AAA
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Smoking Cessation- Single important modifiable RF
Exercise Therapy- Benefit small aneurysms
Beta Blockers- May decrease the rate of expansion?
ACE inhibitors- Evidence is mixed, however,
implicated in less aneurysm rupture.
• Doxycycline
– Antibiotic activiety against chlamydia species
– Suppresses expression of MMP
• Statins - associated with reduced aneurysm expansion
rates. Decreases MMP-9 in aneurysm wall.
EVAR vs. OPEN
• EVAR-1 and DREAM Trials
– Randomized AAA > 5.5 cm to EVAR vs.
open repair
– Lower 30-day mortality for EVAR (1.6%
EVAR vs. 4.6% open)
– Peripop mortality and severe complications
4.7% EVAR & 9.8% open repair (DREAM)
– Similar all-cause mortality at 2 years
– Higher rate secondary interventions in EVAR
– Total cost of Tx & 4 yrs of f/u inc. for EVAR.
Open Repair
•
• Transabdominal Approach
– Previous retroperitoneal
surgery
– Ruptured AAA
– Exposure of mid/distal portions
of visceral vessels or R renal
artery
– R internal or external iliac
artery
– Co-existant abdominal
pathology
– Left-sided vena cava
Retroperitoneal Approach
– Mult. Previous
intraperitoneal
procedures
– Abd wall stoma, ectopic/
anomaly of kidney
– Inflammatory aneurysm
– Proximal aortic access,
endarterectomy of
viceral/renal arteries
needed
– Obese patients
– Fewer GI complications
Open Repair-Complications
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•
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Cardiac
Pulmonary
Renal
Lower Extremity Ischemia
Spinal Cord Ischemia
Incisional Hernia
– 14.2% ventral hernia, 9.7% SBO
• Graft Infection
Open Repair Complications:
Colon Ischemia
– Collaterals from SMA, IMA, internal iliac
artery, and profunda femoris supply
sigmoid colon
– Mortality 40-65%, full-thickness necrosis
80-100%
– Occurs in 0.6-3% of elective and
– 7-27% of ruptured AAA (much more
common endoscopically than clinically)
Colon Ischemia
– Signs and Symptoms
– Bloody bowel movements
– Persistent acidosis & shock
– Treatment
• Ischemia limited to mucosa submucosanpo, IVF, IV abx
• Transmural ischemia- bowel resection,
fecal diversion, creation of ostomy,
washout of abdomen, IV abx.
Open RepairConcomitant Pathology
• Treat most life-threatening process FIRST
• Avoid simult. OR  prosthetic graft infection
• If secondary procedure can be staged without
increased risk - do aneurysm repair first
• Clean procedures (ie:nephrectomy,
oophrectomy) can be performed simultaneously
• GI procedures should not occur at same time
• Abort surgery if metastatic disease or abscesses
which increase risk for graft infection discovered.
Inflammatory AAA
• Perianeurysmal fibrosis & inflammation
• 5% of AAA
• Treatment of AAA resolves the periaortic
inflammation in 53% (open & EVAR)
• Duodenum, left renal vein, and ureters
often involved in inflammation.
• PreOp ureteral stent placement
recommended
Infected AAA
• 0.65% of AAA
• Can be primary or secondary infection
• Potential causes of infection:
– Continguous spread of local infxn, septic embolization
from distal site, bacteremia.
• In the past syphilis and steptococcal species was
common:
– Now: staph and salmonella.
• With HIV and wide-spread abx use- can be caused by
any bacterial or fungal infection
• Dx: fever, abdominal/back pain, high ESR, bacteremia.
EVAR
Types of Endoleak
Types of Endoleak
• Type I
– Usually identified and treated @ time of stent graft implantation
– Must be treated if found on post-op imaging
– Associated with high likelihood of AAA rupture
• Type II
– 10-20% of post-op CT scan show Type II leak
– 80% resolve spontaneously at 6 months
– Indication to treat: persistent leak, aneurysm growth
– Transcatheter tx (coil embolization)
• Type III
– 0-1.5% incidence
– Strong predictor of rupture
– Tx: re-establish continuity by additional component to bridge gap or
cover hole.
• Type IV
– Majority resolve within one month of stent graft implantation
EVAR complications
• Stent-graft infection
– Net infection rate of 0.43%
• Pelvic ischemia
– Internal iliac occlusion during EVAR
– Si/sx: buttock claudication (most common 1650%), buttock necrosis, colon necrosis, spinal
ischemia, lumbosacral plexus ischemia, ED
(15-17%).
– Ischemic colitis < 2%
Discussion
• “No significant difference between endovascular
repair and open repair in rate of overall survival
at a median of 6.4 years.”
• Significantly higher rate of reinterventions in
EVAR group than open group
• Study limited by difference in f/u between the
open and endovascular group.