2: AAA, TAA, Aortic Dissection Flashcards
define an aneurysm
an abnormal dilatation of a blood vessel by more than 50% of its normal diameter
define an abdominal aortic aneurysm
a dilatation of the abdominal aorta greater than 3cm
what are possible causes of AAA
- atherosclerosis
- trauma
- infection
- CT disorders e.g. Marfan’s, Ehler’s Danlos
- inflamm disease e.g. Takayasu’s aortitis
what are risk factors for AAA
- smoking
- HTN
- hyperlipidaemia
- FHx
- male
- increasing age
how might a AAA patient present
- mostly asymptomatic and only detected as an incidental finding/screening
- if symptomatic: abdo pain, back/loin pain, distal embolisation - limb ischaemia
what can be felt on examination of an AAA
pulsatile mass in abdomen above the umbilical level
- rare: signs of retroperitoneal haemorrhage
describe the aneurysm screening programm
- offer an abdominal USS for all men aged 65 years
- men who have been screened have an approx 50% reduction in aneurysm-related mortality
- most men w detected AAA will spend 3-5 years in surveillance prior to reaching threshold for elective repair
what are the main ddx for patients presenting with symptomatic AAA
- renal colic
- diverticulitis
- bowel ischaemia
- degenerative disc disease
- ovarian torsion
what are important investigations in suspected AAA
USS
- once confirmed, follow up CT scan with contrast when threshold diameter of 5.5cm
- provides more anatomical details to determine suitability for endovascular procedures
how are patients with an AAA of less than 5.5cm managed (5)
- monitored via duplex USS
- 3.0-4.4cm: yearly ultrasound
- 4.5-5.4cm: 3 monthly ultrasound - smoking cessation to reduce rate of expansion and risk of rupture
- improve BP control
- commence statin and aspirin therapy
- weight loss and increased exercise
when is surgery indicated in pt w AAA
- AAA >5.5cm
- AAA expanding at >1cm/year
- symptomatic AAA patient who is otherwise fit
- in the UK, AAA>6.5cm must be notified to DVLA and disqualified from driving
what are the main surgical options for AAA
open
endovascular
what does open repair of AAA involve
- midline laparotomy or long transverse incision
- expose the aorta
- clamp aorta proximally and iliac arteries distally
- remove segement
- replace with prosthetic graft
what does endovascular repair of AAA involve
compare and contrast open vs endovascular repair
- endovascular repair has better short term outcomes e.g. decreased hospital stay and 30 day mortality
- but higher rate of reintervention and aneurysm rupture
- after 2 years the mortality for both procedures is the same so in young fit patients, open repair may be more appropriate
what is an important complication for EVAR
endovascular leak
- incomplete seals forms around the aneurysm resulting in blood leaking around the graft
how are endoleaks classified
what are the main complications of AAA (3)
aneurysmal rupture
- retroperitoneal leak
- embolisation
- aortoduodenal fistula
how might a ruptured AAA present
- abdo/back pain
- syncope
- vomiting
- O/E: haemodynamically compromised + pulsatile abdo mass
- 50% classic triad: flank/back pain, hypotension, pulsatile abdo mass
what are the 2 ways in which a AAA can rupture
- anteriorly: into peritoneal cavity and have poor prognosis
- posteriorly: into retroperitoneal space where blood can tamponade itself and promote haematoma formation so better prognosis
how is a ruptured AAA managed
- high flow O2
- IV access x2 large bore cannulae
- urgent bloods + crossmatch for min 6 units
why should patients in shock from ruptured AAA be treated w caution
raising the blood pressure too much will potentially dislodge any clot and may precipitate further bleeding
- aim to keep the BP≤100mmHg (termed ‘permissive hypotension’, preventing excessive blood loss)
what is an aortic dissection
tear in the intimal layer of aortic wall causing blood to pool and split apart the tunica intima and media
what are the different ways in which an aortic dissection can progress
- anterograde: towards iliac arteries
- retrograde: towards aortic valve
- or in both directions from point of origin
what can retrograde aortic dissection result in
- prolapse of aortic valve
- bleeding into the pericardium
- cardiac tamponade
what is a penetrating aortic ulcer
ulcer that penetrates the intima and progresses into the media of the artery
what can a penetrating aortic ulcer progress to
- intramural haematoma
- aortic dissection
- perforation
- aneurysm formation
what are the 2 systems used to classify aortic dissection
Stanford
DeBakey
how does the Stanford classification divide aortic dissection
- type A: involves the ascending aorta and can propagate to the aortic arch and descending aorta (i.e. DeBakey Types I and II) ; tear can originate anywhere along this path
- type B: does not involve the ascending aorta, occurring in any other part of the aortic arch and descending aorta (i.e. DeBakey Type III)
how does the DeBakey classification group aortic dissections (anatomically)
-
Type I – originates in the ascending aorta and propagates at least to the aortic arch
- typically seen in patients under 65yrs and carry the highest mortality, quoted at 1% per hour in the acute setting -
Type II – confined to the ascending aorta
- classically in elderly patients with atherosclerotic disease and hypertension -
Type III – originates distal to the subclavian artery in the descending aorta
- further subdivided into IIIa which extends distally to the diaphragm and IIIb which extends beyond the diaphragm into the abdominal aorta
what are the risk factors of aortic dissection
- HTN
- atherosclerotic disease
- male
- CT disorders
- bicuspid aortic valve
what is the characteristic presentation of acute aortic syndrome + clinical signs
tearing chest pain radiating through to the back
- tachycardia
- hypotension
- new aortic regurg murmur
- signs of end-organ hypoperfusion e.g. reduced urine output, paraplegia, lower limb ischaemia
what are ddx for aortic dissection (4)
- MI – classically crushing and central chest pain, with signs of cardiac ischaemia on ECG and / or raised serum troponin levels
- PE – dyspnoea will be a prominent feature, with potential hypoxia present, can be confirmed with a CTPA (or V/Q scan)
- pericarditis – classically pleuritic chest pain, with the ECG showing diffuse ST elevation, as well as potential pericardial rub on auscultation
- musculoskeletal back pain – the patient will not present with systemic signs of shock and will be tender to palpation of the chest wall or paraspinal muscles
what is the appropriate management for aortic dissection
- baseline blood tests
- crossmatch 4 units packed RBCs
- ECG to exclude cardiac pathology
what are the appropriate imaging options for aortic dissection (2)
- CT angio
- transoesophageal ECHO
what is the urgent initial management of aortic dissection
- high flow oxygen
- x2 large bore IV cannulas
- fluid resus
what is the follow up management of aortic dissection
- antihypertensive therapy
- surveillance imaging (1,3,12 months post discharge)
how are type A dissections treated
high mortality!
- surgery: removal of ascending aorta and replacement with synthetic graft
how are type B dissections treated
- uncomplicated managed medically
- 1st line is managing HTN with B-Blockers e.g. labetalol
- lowers SBP, PP and pulse rate to minimise stress on dissection
in the acute setting, why is endovascular repair of type B dissection not recommended
risk of retrograde dissection
what is the most common complications of type B dissections
can go on to become chronic –> formation of aneurysm
what are possible complications of aortic dissection
- Aortic rupture
- Aortic regurgitation
- Myocardial ischaemia - secondary to coronary artery dissection
- Cardiac tamponade
- Stroke or paraplegia - secondary to cerebral artery or spinal artery involvement
why do thoracic aortic aneurysms develop
degradation of tunica media (provides tensile strength and elasticity) –> loss of structural integrity and dilates
- diameter increases - rise in tension - further diameter increase
where do thoracic aortic aneurysms commonly affect
- ascending aorta or aortic root (60%)
- aortic arch (10%)
- descending aorta (40%)
- thoracoabdominal aorta (10%) segments
what are the 2 main causes of thoracic aortic dissection
- CT disorders
- bicuspid aortic valve
what are the clinical features of thoracic aortic aneurysms
chest pain - depending on site of aneurysm
* Ascending aorta – anterior chest pain
* Aortic arch – neck pain
* Descending aorta – posterior thoracic pain
what are secondary symptoms of thoracic aortic aneurysms (3)
- back pain (spinal compression)
- hoarse voice (damage to left RLN in arch aneurysm)
- heart failure (involvement of aortic valve)
what are appropriate investigations into thoracic aneurysms
- routine bloods
- ECG
- CXR
what might a CXR of thoracic aneurysm show
- widened mediastinal silhouette
- enlarged aortic knob
- possible tracheal deviation
what is the preferred imaging modality of thoracic aneurysms
CTA
- can visualise sac and lumen and detect potential complications e.g. rupture or mural thrombus
what are patients with confirmed thoracic aneurysms started on
medical management
- statins
- anti-platelet therapy
- smoking cessation
when is surgical intervention indicated for thoracic aneurysms
- Ascending Aorta – diameter >5.5cm, the affected region of the aorta is excised and replaced with a dacron graft; if the aortic root is involved, a Bentall procedure is often performed, using a graft that also contains a prosthetic aortic valve
- Aortic Arch – aneurysm is over 5.5cm; affected aorta is replaced with a multi-limbed graft, allowing for the branching of the great vessels (such procedures have a high risk of cerebral ischaemia from embolisation)
- Descending Aorta – diameter exceeds 6.0cm; open or with endovascular
