Abdominal Aortic Aneurysm Flashcards
What is an aneurysm?
- Defined as a blood vessel more than 50% it’s usual diameter (1.5x)
- AAA defined as dilatation abdominal aorta more than 3cm - normal diameter is 2cm
Cause of AAA
Largely unknown.
Possible causes inc:
* Atherosclerosis
* Trauma
* Infection
* Connective tissue disease (eg Ehlers danlos/Marfans)
* Inflammatory disease (eg Takayasu aortitis)
RF for AAA
- Smoking
- HTN
- Increasing age
- Male gender
- Hyperlipidaemia
- FH
Diabetes mellitus is actually a NEGATIVE RF - mechansim not understood
Clinical features
- Asymptomatic
- Usually detected during screening or incidentally
- If symptomatic - inc abdo pain, back/loin pain, distal embolisation (limb ischaemia)
- If ruptured - shock/syncope
Examination findings AAA
- Pulsatile mass
- Above umbilical level
- Rarely - signs of retroperitoneal haemorrhage
Screening for AAA
- Abdominal USS for all men aged 65
- Screening results in 50% lower mortality rate
Management depending on AAA screening result
Differentials for AAA
- Renal colic
- Diverticulitis
- Bowel ischaemia
- Degenerative disc disease
- Ovarian torsion
Investigations for AAA
- Duplex USS
- Once confirmed CT angiography scan with contrast if 5.5cm or more
- Group and save and clotting screen - blood and loss
- Crossmatch for surgery
- U&Es - for contrast
- FBC - low platelet?
Medical and lifestyle management of AAA
If less than 5.5cm:
* Monitoring as appropriate (mentioned above)
* Smoking cessation
* Weight loss
* Increased exercise - avoid strenous, contact sports and heavy lifting though
* Improve BP control
* Statin and aspirin therapy
When is surgery considered for AAA?
- If AAA greater than 5.5cm in diameter OR
- If increasing at more than 1cm per year OR
- Symptomatic in otherwise well person
Surgical management of AAA
- Open repair OR
- Endovascular repair (EVAR)
Open repair AAA
- Midline laparotomy (xiphisternum to pubic symphysis) or long transverse incision
- Expose aorta
- Clamp aorta proximally and iliac arteries distally
- Segment then removed and replaced with synthetic graft
Endovascular repair for AAA
Open repair vs endovascular suitability
Open:
* Any shape (eg if involving renal and iliac arteries)
* Need good baseline function - general anaesthetic, laparotomy
* Cross clamping = huge afterload = cardiac stress could cause cardiac arrest
Endovascular:
* Good for very frail patients - only need incision in groin and local anaesthetic
* Suitable for those with significant cardiac disease - no cross clamping
* Not suitable if involves renal arteries and need to be able to access femoral artery for catheter
Complication of endovascular repair
- Endovascular leak
- Blood leak arounds graft due to incomplete seal
- Often asymptomatic - need surveillance - USS usually
Level aorta pierces diaphragm
T12
Aorta anatomy
- Split into thoracic and abdominal aorta (usuing diaphragm)
- Thoracic = ascending, arch and descending
- Abdominal - supra-renal, juxtarenal and infrarenal
Where are 90% of AAA?
90% infrarenal
Abdominal aorta branches
Where does abdominal aorta divide into iliac vessels?
L4
Whos AAA is more likely to rupture?
- If female (but men more likely to have to begin with)
- Larger AAA
- Smoking
- HTN
Not all rupture
Classification of AAA options
- Location - thoracic, abdominal (suprarenal vs juxta vs infrarenal)
- Size - most common
- Wall - true vs false (true consists of all 3 layers of vessel wall, false only involves intima)
- Aetiology
- Morphology - fusiform (both sides wall) vs saccular (one sides)
Pathophysiology with AAA
- Atheroma = inflammatory reaction
- = release of metalloproteases enzyme release from inflammatory cells
- = damage to internal and external elastic lamina of aortic wall
- = loss of elasticity and ability to cope with pressure changes during
- = dilatation
- Then fibrosis occurs = loss of more elasticity, thinning and loss of strength
- = weaker than systolic pressure
- = rupture
Referral size of AAA
- If 5cm females for 5.5cm male = seen within 2 weeks
- 3-5.4cm - seen within 3 months
Main complication of AAA
- Ruptured - anteriorly (20%) into peritoneal cavity or posterolaterally (80%) into retroperitoneal space
- Posterolaterally can be temporarily tamponaded by anatomy sometimes
Endoleaks classification
- Type 1 - proximal (1a) or distal (1b) site attachment leaks
Risks of AAA surgery
- Endoleak in EVAR
- Abdominal compartment syndrome - compressed IVC and reduced renal perfusion
- Erectile dysfunction
- Acute limb ischaemia - emboli from clot in AAA or injury to lower limb vessels
- Graft infection
- Blood transfusion complications
When is surgery not suitable
- Patient preference
- Size
- Progression
- Co-morbidities
- Baseline
- Ceiling of care
- Risk > benefit
- Life expectancy
–> palliative care
Manageemnt ruptured AAA
- Patient unstable, they will require immediate transfer to theatre for open surgical repair
- If the patient is stable, they will require a CT angiogram to determine whether the aneurysm is suitable for endovascular repair
