Vascular: AAA Flashcards
What is an aneurysm? What is a AAA?
Aneurysm = abnormal dilatation of a blood vessel by >50% its normal diameter.
AAA = dilatation of abdominal aorta >3cm.
Which conditions can predispose to AAA?
- Connective tissue disease, e.g. Marfan’s, Ehlers-Danlos
- Inflammatory disease, e.g. Takayasu’s aortitis
- Atherosclerosis, trauma, infection
Suggest risk factors for AAA.
- smoking
- hypertension
- hyperlipidaemia
- male gender
- increasing age
- family history
Describe the AAA screening programme in the UK.
Abdo USS offered to all men in 65th year.
Around 1.1% of those screened are diagnosed with an AAA, with 0.32% having an AAA large enough (>5.5cm) to require direct referreal for surgery consideration.
Most men with a detected AAA will spend 3-5yrs in surveillance prior to reaching threshold for elective AAA repair.
What is the presentation of a AAA?
Many AAA are asymptomatic.
Classic triad in <1/3 pts:
- abdo. back or loin pain
- tender pulsatile mass a few cm above umbilicus
- hypotension (weak, thready pulse)
Suggest 4 DDx for AAA.
- MI with cardiogenic shock
- Massive PE
- Acute pancreatitis
- Renal colic
Name 3 complications of AAA.
- Rupture and haemorrhage
- Distal embolisation producing limb ischaemia
- Aortoenteric fistula
How would you investigate (initial and follow-up) a non-ruptured AAA.
Initial: abdo USS if suspected AAA in routing outpatient setting
Follow-up: contrast CT scan when >5.5cm to provide more anatomical detail and determine suitability for endovascular procedures.
How would you manage a Pt with a non-ruptured AAA?
- Monitoring via duplex USS for any AAA <5.5cm
- 3-4.4 cm: yearly USS
- 5-5.4 cm: 3 monthly USS - Decrease cardiovascular risk factors (3% per yr risk of CVD mortality):
- smoking cessation (decrease rate of expansion and risk of rupture)
- improve BP control
- commence statin and aspirin therapy
- weight loss and increased exercise - Surgery considered for AAA >5.5cm, AAA expanding at >1cm/yr or a symptomatic AAA in a pt who is otherwise well.
- open repair (replacement with prosthetic graft)
- endovascular repair
What are the 2 main types of AAA rupture. Which has the better prognosis?
- Retroperitoneal (80%)
- rupture posteriorly into retroperitoneal space
- usually survive to get to hospital
- leak is contained but will eventually rupture intraperitoneally - Intraperitoneal (20%)
- rupture anteriorly into peritoneal cavity
- immediately fatal (abdo. cavity has capacity for 23L of fluid and CO is 5L/min)
What is the presentation of AAA rupture?
- sudden severe abdo/back pain
- nausea and vomiting
- shock: tachycardia, low BP, clammy, LOC
Describe your initial management of someone with a ruptured AAA.
ABCDE
- O2 15L/min
- IV access in antecubital fossa (2x large bore cannulae)
- Urgent bloods taken (FBC, UandEs, clotting) with cross-match for min. 6 units
- IV fluids to maintain systolic at <100mgHg (permissive hypotension)
- catheterise
- contact vascular surgeon ASAP
- if stable Pt, require CT angiogram to determine if aneurysm suitable for endovascular repair
- if unstable Pt, immediate transfer to theatre for open surgical repair
Why is a Pt with ruptured AAA maintained in permissive hypotension?
Raising BP could dislodge a clot and precipitate further bleeding
What is the prognosis of someone with a AAA rupture?
Overall mortality is 83% - most die of multi-organ failure from huge blood loss:
- 50% die at home
- of 50% entering hospital, 70% operable and survival in these is 50%
Describe an important complication of EVAR.
- Endovascular leaking – important complication of EVAR, where an incomplete seal forms around the aneurysm resulting in blood leaking around the graft. Often asymptomatic so regular USS surveillance needed. If left untreated, aneurysm can expand and subsequently rupture.
