Abdominal Aortic Aneurysm Flashcards
Define aneurysm
Permanent localised dilatation of artery with increase in diameter more than 1,5 times the expected size or adjacent normal artery. 3 cm for AAA
Define arteriomegaly
Diffuse arterial enlargement with an increase in diameter more than 50% above normal or expected
Define ectasia
Permanent localized dilatation of an artery <50% of normal diameter
Define pseudo aneurysm
Contained extravasated blood from a disruption in the arterial wall, doesn’t contain all 3 layers of the vessel.
Name and describe 2 morphological types of aneurysms
• Saccular: only part of the vessel circumference
• fusiform: entire circumference
Name 7 causes aneurysm.
• Degenerative (used to be called atherosclerotic): most common
• Infection: HIV, bacterial eg S aureus, syphilis
• pseudo-aneurysm: trauma and anastomotic breakdown
• connective tissue disorders: marfan, ehlers-danlos syndrome
• inflammation: Takayasu’s disease
• post stenotic: thoracic outlet obstruction, coarctation
• aortic dissection
• intimal medial mucoid degeneration
Name 6 risk factors degenerative aneurysms
Host
• Male
• Caucasian
• family history, especially if the relative is female
Lifestyle
• smoking
Medical conditions
•Hypertension
• hypercholesterolaemia
Pathogenesis aneurysms? (4)
Multifactorial:
• proteolytic degradation of aortic wall connective tissue (elastin and collagen through matrix metalloproteinase mmp)
• inflammation and immune response: macrophages and neutrophils → cytokine release → protease activation
• biochemical wall stress (berry aneurysms more common in infra-renal segment because less elastin (dilatation) and collagen (rupture))
• molecular genetics: less type 3 collagen
Symptoms AAA? (10)
• 75% asymptomatic!
• Local compression:
- d3 d4 duodenal compression → early satiety, nausea, vomiting
- left ureter compression → obstructive uropathy, recurrent UTI
- erode vertebral bodies → back pain
• Acute rupture 20%, triad in 50%:
- acute abdominal pain
- haemodynamic instability
-Pulsatile abdominal mass
• emboli
- distal macroembolism → acutely threatened limb
- distal microembolism → blue toe syndrome
• fistula (rare): aorto-duodenal, aorto-caval
Clinical examination AAA? (4)
• bimanual abdominal palpation
• size. Expands laterally
• bruit on auscultation
• palpable thrill
Investigations for AAA? (3)
• Duplex ultrasound: first line to confirm clinically suspected AAA, and best for screening and surveillance
• multidetector CTA: most accurate to get details.. Demonstrates extent, calibre, size, degree of calcification, neck characteristics, mural thrombus presence, vascular anomalies eg horseshoe kidney, relationship to renal arteries and left renal vein.
• MRA: similar results CT, only do if kidney failure so can’t handle contrast, pregnant ( less radiation) or risk distal embolisation.
Catheter directed angiography reserved for endovascular procedures
Name 4 reasons that screening for AAA is important, and how and when to do it
From age 65 with duplex ultrasound
• most AAA asymptomatic
• primary aim in managing AAA is to prevent rupture
• morbidity and mortality of repair of ruptured AAA is 50-70 % compared to 1-5% for elective repair
• patients who survive repair have similar life expectancy as general population
Indications to repair AAA? ( 5)
If risk of rupture outweigh operative risk! These risks include:
• size: male 5,5 cm, 5,0 cm female
• expansion rate > 1cm/year (0,5cm/6 months)
• factors associated with increased expansion rate: smoking, COPD
• symptomatic eg compression, embolism, fistula
Preoperative assessment of elective AAA repair? (3)
• ECG and echo (cardiac function )
• 24 hour creatinine clearance (renal function)
• lung function tests.
Patients must be fit for open surgery, high risk can be offered endovascalar EVAR if meet requirements
Management AAA? (5)
Non-operative: prevent small aneurysms from enlarging or decrease expansion rate of large
• Best medical therapy: ace-inhibitors, statins, aspirin, stop smoking, exercise, control diabetes
. Best medical therapy must reduce rate of expansion by > 50% to keep a 4.0cm aneurysm from reaching the 5.5cm threshold within 5 years.
• ultrasound surveillance
- 3 monthly for 4.5-5,5cm
-6 monthly for 3-4.5 cm
• no benefit in early surgery over surveillance for small aneurysms
Only operate when meet 1 or more of the 3 risks of rupture. Options include open surgery or evar
How is elective open repair of AAA done?
Transperitoneal (preferred) or retroperitoneal.
Name 5 indications for retroperitoneal instead of transperitoneal elective open repair of AAA
• Hostile abdomen: urinary or enteric stoma, previous abdominal or pelvic irradiation, ascites, morbid obesity, prior abdominal surgery.
• inflammatory aneurysms
• aneurysms associated with horseshoe kidneys
• suprarenal aneurysms
• renal ectopy
Name 6 early complications of elective open repair of AAA
• Cardiorespiratory failure
• Haemorrhage
• renal failure
• limb ischaemia
• colonic ischaemia
• venous thromboembolism
Name 3 late complications of elective open repair of AAA
• Graft sepsis
•Pseudo aneurysms
• aorto-enteric fistula
How is endovascular AAA repair (evar) done?
Exclusion of AAA from ischaemic circulation by means of pre-op sized deployment stent graft, preventing further aneurysm expansion and elimination of rupture risk
Lower mortality than open but less durable
Name 6 patient selection requirements for endovascular AAA repair (evar)
Aneurysm neck morphology
• straight neck, minimal length of 1 cm
• minimum of 15 mm for 60° angulation
• max diameter 3cm
Funnel shaped neck, thrombus extending to neck, excessive calcifications = contraindications!
Iliac vessels
• iliac arteries of sufficient calibre > 7 mm to tolerate passage of graft
Aortic bifurcation
• diameter must be wide enough to accept both graft limbs without their compressing each other (2cm)
Name 8 complications EVAR
• iatrogenic vessel injury
• endoleak: arterial flow of blood into excluded aneurysm sac but outside lumen of the deployed stent graft
• embolisation
• graft migration, dislocation and displacement
• post-implant syndrome: early back pain and fever without leucocytosis
• contrast nephropathy
• graft sepsis
• Graft limb thrombosis
How often should post-op surveillance for complications be performed after AAA repair?
CTA and duplex ultrasound before discharge, at 1 month, month 6, year 1 then yearly
Clinical presentation ruptured AAA?
50% present with classic triad:
• acute abdominal pain
• hypotension
• pulsatile abdominal mass
Initial management ruptured AAA?
Resuscitation with permissive hypotension to maintain organ perfusion. Get ready for theatre.
Patient selection for ruptured AAA surgical repair? (5)
Hardman criteria.
• age >70
• creatinine >190 mmol/l
• hb <9 g/dL
• ECG evidence of ischaemia
• loss consciousness
≥ 3 factors predict a mortality of 100% and shouldn’t be repaired
How is surgical repair of ruptured AAA achieved?
Open repair: supraceliac aorta exposure and clamping
• midline laparotomy
• retract left lobe of liver to right and open gastro hepatic ligament to allow into lesser sac
• NGT used to identify esophagus and stomach. Retract to left.
• Aorta identified between crura of diaphragm. L crus may be split with cautery to allow clamp placement
EVAR: preferred
Rapid control haemorrhage by inflation aortic balloon in suprarenal aorta
