Abdominal Aortic Aneurysms Flashcards
Define an aneuryseum
Permanent localised dialtion of an artery more than 50% of the normal diameter of the artery
Define ectasia
Localised area of enlargement in the artery but less than 1.5x (therefore not dilated enough to be called an aneurysm)
Define arteriomegaly
Generalised enlargement of arterial tree
Describe the difference between:
- True aneurysm
- False aneurysm
- True: pathological degeneration involving all or part of vessel wall leading to dilation of vessel of at least 1.5x normal size
- False (also known as pseudoaneuryms): wall is ruptured and there is collection of blood (haematoma) external to vessel bounded externally by adherent extravascular tissues
Where in body do aneurysms occur?
- Aorta
- Popliteal artery
- Common femoral arteries
- Intra-abdominal sphlanchnic arteries
- Subclavian arteries
- Carotid arteries
Answer the following:
Which sex are aneurysms more common in?
What ethnicity are aneuryseums more common in?
- Male (4:1)
- Caucasians
What is a AAA?
Abdominal aortic aneurysm= dilatation of the abdominal aorta greater than 3cm
State some potential causes of AAA
- atherosclerosis
- trauma
- infection
- connective tissue disease (e.g. Marfan’s disease, Ehler’s Danlos, Loey Dietz)
- inflammatory disease (e.g. Takayasu’s aortitis).
State some risk factors for AAA
- Underlying connective tissue disorder
- Risk factors for peripheral vascular disease
- Smoking
- Hypertension
- Hyperlipidaemia
- Hypercholesterolaemia
- Obesity
- Poor diet (high in trans fat, low in fruit & veg)
- Lack of exercise
- Male
- Family history
- Older age
Diabetes is a negative risk factor for AAA; true or false?
True
Discuss how a AAA usually presents
- Often asymptomatic and found incidentally on examination or abdo x-ray
- Symptoms of peripheral vascular disease
- Non-specific abdominal pain, back pain, loin pain
- Palpable expansile pulsation in abdomen
- Aortoenteric fistula
- Symptoms & signs due to distal emboli e.g. ischaemia
Where is the most common site for AAA?
Infrarenal
Discuss whether we screen for AAA in the UK
- NAAASP (National Abdominal Aortic Aneurysm Screeening Programme)
- Offer abdo ultrasound to all men in their 65th year
- Around 1.1.% of all those screened are diagnosed with AAA; only 0.32% have large enough AAA to require direct referral for consideration of surgery. Most men with AAA spend 3-5yrs in surveillance prior to reaching threshold for surgery
NOTE: Women are not routinely offered screening, as they are at much lower risk. The NICE guidelines (2020) say a routine ultrasound can be considered in women aged over 70 with risk factors such as existing cardiovascular disease, COPD, family history, hypertension, hyperlipidaemia or smoking.
Discuss what investigations you would want for a pt with suspected AAA
- Ultrasound scan
- A follow up CT angiogram when aneurysm is at threshold diameter of 5.5cm; this provides more anatomical detial to assess suitability for endovascular repairs
- May consider blood tests for risk factors e.g. lipids, HbA1c etc..
Why is an AXR not indicated in a AAA?
AXR will rarely show AAA unless there is significant calcification of the arterial wall
Roughly, at what rate do anuerysms expand?
10% per year
We have already said that the threshold for surgery is 5.5cm, discuss how you would manage an AAA that is:
- 3 - 4.4cm
- 4.5 - 5.4 cm
Patients with an aorta diameter above 3cm are referred to a vascular team (urgently if more than 5.5cm). Small aneurysms (3 - 5.4cm) should be managed by:
- Monitor AAA via duplex ultrasound
- 3 - 4.4cm= yearly
- 4.5 - 5.4cm= 3 monthly
- Reducing cardiovascular risk factors:
- Lifestyle e.g. stop smoking, weight loss
- Hypertension control (if appropriate)
- Statin
- Aspirin
Discuss the DVLA rules in regards to AAA
Gov.uk (April 2021) advise that patients must:
- Inform the DVLA if they have an aneurysm above 6cm
- Stop driving if it is above 6.5cm
- Stricter rules apply to drivers of heavy vehicles (e.g., bus or lorry drivers)
State the 3 indications for surgery for a AAA
- >5.5cm
- Aneurysm that is larger than 4cm and expanding at >1cm per year
- Symptomatic AAA in pt who is otherwise fit and well
Describe the two surgical options for AAA
- Open repair: midline laparotomy or long transverse incision exposing the aorta. Clamp the aorta proximallly and the iliac arteries distally. Insert graft.
- Endovascular repair: introducing a graft via the femoral arteries and fixing the stent across the anuerysm
Compare the outcomes of open repairs and endovascualr repairs, consider:
- Short term outcomes
- Long term outcomes
Short Term Outcomes
- Endovascular has shorter hospital stay and lower 30 day mortality
- Endovascular has higher rate of reintervention and aneurysm rupture
Long Term Outcomes
- After 2yrs the mortality for both procedures is the same
- …. therefore, often do open repair in young, fit pts.*
State some potential complications of AAA
- Rupture
- Embolisation
- Retroperitoneal leak
- Aortoduodenal fistula
State some complications of open repair of AAA
- Haemorrhage
- Embolisation/thrombosis of distal arterial tree
- Colonic ischaemia
- Infection
- Respiratory complications
- Renal failure
- Cardiac events
State some complications of endovascular repair of AAA
- Endoleak
- Graft migration
- Fracture of supporting wires
- Endotension
An important complication for EVAR (endovascular aneurysm repair) is endovascular leak (“endo-leak”), discuss:
- What this is
- Whether they are symptomatic
- What is done to prevent endoleaks
- Classification
- Graft forms an incomplete seal forms around the aneurysm hence blood leaks around the graft into the aneurysm
- Often asymptomatic
- Hence regular USS surveillance for this complication
- If left untreated, aneurysm could expand & rupture
- Type 1 to 5
For pseudoaneuryseums, discuss:
- Potential causes
- Where most commonly occur
- Signs & symptoms
- Differentials
- Causes: damage to vessel wall e.g. following cardiac catheterisatoin or repeated injections such as IVDU, trauma, regional inflammation, vasculitis
- Most common at femoral artery
- Signs & symptoms: pulsatile lump which can be tender and painful, may be compressing artery and occluding blood flow distally therefore may be signs of ischaemia, if infected will be erythematous and purulent material may be discharging and may have septic features
- Differentials: haematoma, abscess, true aneurysm
For pseudoaneurysms, discuss:
- Investigations
- Investigation findings
- Management
- Investigations:
- Distal pulse status examination
- Duplex ultrasound
- CT imaging may be used if access difficult with USS
- If infected, bloods (FBC, U&Es, CRP, clotting, blood cultures, swab/discharge MC&S, cross match- as higher risk of bleeding if infected)
- Management:
- Small= left alone
- Larger or symptomatic:
- USS guided compression
- or USS thrombin injection
- or endovascular stenting
- Surgical repair or ligation
- Infected:
- Pressure dressing applied immediately and urgent imaging
- Surgical ligation (this may require a bypass graft due to risk of acute limb ischaemia). Collateral supply can provide adequete flow in most cases however small proprotion of people will end up needing subsequent amputations
Explain the difference between a stent and a graft
Stents
- Made of metal (alloy that expands at body temperature so is continually pushing outwards)
- Can be covered or uncovered
- Can only be intraluminal
Grafts
- Not made of metal
- Always covered
- Can be intraluminal or extraluminal (i.e. used as a bypass)
Explain the difference between a duplex scan and
“duplex” refers to the fact that two modes of ultrasound are used, Doppler and B-mode. The B-mode transducer (like a microphone) obtains an image of the vessel being studied. The Doppler probe within the transducer evaluates the velocity and direction of blood flow in the vessel.
*Doppler records sound waves that bounce off moving objects.
Of all the men screened when they are 65yrs, what % have AAA?
<1%
Why do we operate on AAAs at 5.5cm?
At 5.5cm risk of dying from rupture and risk of dying from surgery are equal
