- An AAA is an increase in aortic diameter by greater than 50% of
normal
- Usually regarded as aortic diameter of greater than 3 cm diameter
- More prevalent in elderly men
- Male : female ratio is 4:1
Picture provided by Peter Lin, Baylor
College of Medicine, Houston, Texas, USA
- Risk factors – hypertension, peripheral vascular disease, family
history
- Accounts for 2% male deaths above the age of 55 years
- 3000 elective and 1,500 emergency operations in UK each year
- Mortality of emergency operation is greater than 50%
- Mortality of elective surgery is less than 5%
- Selection of patients for operation depends on risk of operation vs.
risk of rupture
Natural history
- AAA diameter expands exponentially at approximately10% / year
- Risk of rupture increases as aneurysm expands
- 5 year risk of rupture:
- 5.0 – 5.9 cm = 25%
- 6.0 – 6.9 cm = 35%
- More than 7 cm = 75%
- Overall only 15% aneurysms ever rupture
- 85% of patients with a AAA die from an unrelated cause
Screening
- AAA are suitable for screening as elective operation of asymptomatic
aneurysms can reduce mortality associated with rupture
- Who should be screened is controversial
- Probably males over 65 years especially hypertensives
- Single US at 65 years reduces death from ruptured AAA by 70% in
screened population
- Patients with small aneurysms should undergo regular surveillance
- Repeated ultrasound every 6 months
Multicentre Aneurysm Screening Study (MASS)
- Randomised study looking at the effect of serial US on AAA-related
mortality
- Men 65-74 years invited for screening
- 80% uptake achieved
- Aneurysm detection rate = 5% with 12% more than 5.5.cm
- Mean follow-up was 4 years
- Primary outcome was aneurysm-related mortality
- Secondary outcomes were 30-day all cause mortality and
health-related quality of life
- Aneurysm detection through screening decreased rate of emergency
repair by 50%
- Over the trial period, aneurysm-related mortality was lower in the
screened group
- 30 day mortality was
- 6% after elective repair
- 37% after emergency repair
- Mean additional cost of screening was £63 per patient
- Equated to £28,400 per life year gained
Clinical features
- 75% are asymptomatic
- Possible symptoms include
- Epigastric pain
- Back pain
- Malaise and weight loss (with inflammatory aneurysms)
- Rupture presents with
- Sudden onset abdominal pain
- Hypovolaemic shock
- Pulsatile epigastric mass
- Rare presentations include
- Distal embolic features
- Aorto-caval fistula
- Primary aorto-intestinal fistula
Indication for operation
- Rupture
- Symptomatic aneurysm
- Rapid expansion
- Asymptomatic > 6 cm – exact lower limit controversial
UK Small Aneurysm Trial
- Randomised 1090 small aneurysms (4.0-5.5 cm) to operation or
surveillance
- Showed no improvement in overall mortality for those offered early
surgery
- Similar results obtained in US Aneurysm Detection and Management
Study
Pre-operative investigation
- Need to determine
- Extent of aneurysm
- Fitness for operation
- Ultrasound, conventional CT and more recently spiral CT
- Determines – aneurysm size, relation to renal arteries, involvement
of iliac vessels
- Most significant post op morbidity and mortality related to cardiac
disease
- If pre-operative symptoms of cardiac disease need cardiological
opinion
- May need thallium scan or cardiac catheterisation
- Cardiac revascularisation required in up to 10% patients
Picture provided by Andrew McIrvine,
Darwent Valley Hospital, Dartford, United Kingdom
Endovascular aneurysm repair
- Introduced into clinical practice with few clinical trials over the
past 10 years
- Exact role unclear and medium and late-complications only recently
recognised
- Morbidity of conventional open aneurysm surgery related to:
- Exposure of infra-renal aorta
- Cross clamping of aorta
- Endovascular repair may be associated with:
- Reduced physiological stress
- Reduced morbidity
- Reduced mortality
Technique
- Endovascular repair achieved by transfemoral or transiliac placement
of prosthetic graft
- Proximal and distal cuffs / stents anchor graft
- Exclude aneurysm from circulation
- Three main types of graft
- Aorto-aortic
- Bifurcated aorto-iliac
- Aorto-uniiliac graft with femoro-femoral crossover and
contralateral iliac occlusion
- Use of technique depends on aneurysm morphology
- Aneurysm morphology is best assessed with spiral CT
- Only about 40% of aneurysms suitable for this type of repair
- Aorto-aortic grafts less frequently used due to high complication
rate
- Successful stenting associated with reduced aneurysm expansion
- Still has 1% per year risk of aneurysm rupture
Complications
- Graft migration
- Endovascular leak
- Graft kinking
- Graft occlusion
Popliteal artery aneurysms
- Defined as a popliteal artery diameter greater than 2 cm
- Account for 80% of all peripheral aneurysms
- 50% are bilateral
- 50% are associated with an abdominal aortic aneurysm
- 50% are asymptomatic
- Symptomatic aneurysms present with features of:
- Compression of adjacent structures (veins or nerves)
- Rupture
- Limb ischaemia due to emboli or acute thrombosis
- Treatment is by proximal and distal ligation
- Revascularisation of the leg with a femoropopliteal bypass
- With a symptomatic popliteal aneurysm 20% patients will undergo an
amputation
Picture provided by Luke Evans, Norfolk
and Norwich Hospital, United Kingdom
Bibliography
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aneurysms. Surgeon 2006; 4: 83-85
Gorham T J, Taylor J, Raptis S.
Endovascular treatment of abdominal aortic aneurysm. Br J Surg
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Hinchcliffe R J,
Hopkinson B R. Endovascular repair of abdominal aortic aneurysm:
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47: 523-527.
Lederle F A, Wilson S E, Johnson G R et al.
Immediate repair compared with surveillance of small abdominal aortic
aneurysms. N Eng J Med 2002; 346: 1437-1444.
Lindbolt J S. Screening for abdominal aortic
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Norwood M G, Lloyd G M, Bown M J et al. Endovascular
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