Aortic Aneurysm + Dissection Flashcards
What are aortic aneurysms?
Aneurysm:
- Permanent and irreversible dilatation of blood vessel by >50% of its normal expected diameter
- True aneurysm = involves all three layers of arterial wall (
- False aneurysm = blood leaking through arterial wall but is contained by the adventitia or surrounding perivascular tissue
Location:
- Abdominal (AAA) - majority
- Thoracic (TAA): ascending aorta, aortic arch, descending aorta and thoraco-abdominal aorta
What is the epidemiology of aortic aneurysms?
AAA:
- 6x lower in women, but the rate of rupture is significantly higher
TAA:
- Incidence unknown, prevalence possibly 3-4% of those aged >65yrs
What is the aetiology of aortic aneurysms?
Personal risk factors:
- Male sex
- Increasing age
- FHx +ve
- Smoking
- Weight lifting, cocaine and amfetamine use (risks for rupture due to BP increases)
Conditions increasing the risk:
- Atherosclerosis, hyperlipidaemia
- Connective tissue disorders e.g. Marfan’s, Ehlers-Danlos syndrome type IV
- Aortitis e.g. from GCA, RA
- Infections e.g. tertiary syphilis, HIV
- Trauma
- HTN
- COPD
- CKD
What is the pathophysiology of aortic aneurysms?
Complex:
- Inflammation, proteolysis and reduced survival of smooth muscle in aorta
- Once it reaches a critical diameter, all distensibility is lost, making rupture likely following a spike in BP
- c.2cm normal, >3cm = aneurysm, 6-7cm = critical diameter
TAA:
- 51% are of the ascending aorta, 38% of the descending, 11% in the arch
AAA:
- Most arise at a level LOWER than the renal arteries
How do unruptured aortic aneurysms present?
Most are asymptomatic
- Incidental finding on clinical examination or scans (USS, CT/MRI, sometimes XR)
Other possible presentations are due to a mass/pressure effect:
TAA:
- Chronic pain in chest, neck, upper/mid back or epigastrium (depends on location of aneurysm; possibly also due to erosion of vertebral body)
- Hoarseness of voice (recurrent laryngeal nerve compression), cough, stridor or dyspnoea
- SVCO
- Dysphagia
AAA:
- Chronic pain in back, abdomen, loin or groin (possibly also due to erosion of vertebral body
- May also find pulsatile abdominal swelling
May also present with thrombo-embolic symptoms:
- Arterial emboli, limb ischemia
- DIC
How do you investigate possible aortic aneurysms?
AAA:
- Bimanual palpation of supra-umbilical region can detect between 60-80% of aneurysms depending on size
- Possible bruit
TAA + AAA:
- Bloods: FBC, clotting, renal function and LFT; cross-match (if surgery planned); ESR/CRP if inflammatory/infective cause suspected
- ECG, CXR, ?lung function tests
- Scans: USS (transthoracic and transabdominal); then contrast enhanced CT for detailed views (or MRI if contraindication to contrast)
How does aortic aneurysm rupture present?
Acute, severe pain:
- Depending on structures involved may radiate e.g. though to the back
Haemodynamic instability:
- Hypotension, syncope, collapse and shock
- May also result in sudden death
TAA:
- Haemoptysis can occur
- Can bleed into mediastinum and cause cardiac tamponade and rapid death
AAA:
- Intraperitoneal rupture is usually dramatic and fatal; reteroperitoneal rupture may be contained initially by a temporary seal forming
What is an aortic dissection?
A condition affecting the thoracic aorta
The disruption of the medial layer of the wall of the aorta provoked by intramural bleeding and leading to separation of aortic wall layers
- Forms a true lumen and a false lumen +/- communication
Timescale:
- Acute = <14 days since onset
- Subacute = 15-90 days
- Chronic = >90days
Stanford classification:
- Type A = ascending aorta (DeBakey types I and II)
- Type B = not the ascending aorta (DeBakey type III)
How does aortic dissection present?
Often in two phases:
1) Severe pain, loss of pulses, then the bleeding stops and person stabilises
- Pain = ‘ripping’ / ‘tearing’, often severe and maximal at the time of onset (but can be mild), pain migrates as dissections progress
- HTN also very common, can be a differnece in BP in limbs on R and L of body
- Other vessel involvement due to their occlusion by dissecting process (coronary arteries > angina; spinal arteries > paraplegia; carotid > neuro deficit)
2) Pressure exceeds critical limit and rupture occurs - into pericardium (so tamponade), pleural space or mediastinum
What urgent investigations do you need for suspected aortic dissection?
ECG:
- Some patients will have signs of MI or other ischemic changes
USS:
- Indicate site and extent of dissection
- MRI - confirm Dx, identify other vessel involvement
- CT can be used to confirm Dx but is less helpful in complications and prognosis
What urgent investigations do you need for suspected aortic aneurysm rupture?
Bloods:
- FBC
- Clotting
- Renal + liver function
- Cross-match
ECG
Contrast enhanced arterial-phase CT angiography (or MR angiography but only if stable)
- ‘Crescent sign’ = blood within the mural thrombus
How do you manage a ruptured aortic aneurysm?
IV access
- Large bore cannula
- Preferably before hospital
Group and cross-match for blood, also make platelets and fresh-frozen plasma available
Arrange theatre immediately + experienced anaesthetist as haemodynamic instability likely
Open repair preferred
How do you manage an aortic dissection?
- IV access
- Adequate analgesia
- ICU/HDU transfer
- Possible need for blood products
Aggressively manage HTN to reduce further damage
- IV betablockers to reduce the force of ventricular contraction
Surgery:
- Prevention of aortic rupture, pericardial tamponade and to relieve aortic regurgitation
- Stents or grafts
- Done open or via an endovascular route (TEVAR)
Who needs surgery for aortic aneurysms?
Immediate if:
- Rupture
- Some types of dissection
- Acute symptoms (as these suggest impending rupture/dissection)
How do you medically manage aortic aneurysms?
General
- BP control with BBs to reduce shear stress
- Smoking cessation
- CV risk factor modification including statins
- Anti-platelets where appropriate
TAA:
- CT/MRI every 6/12
AAA:
- NHS AAA screening programme
- USS at a frequency dictated by size of aneurysm e.g. 3-4.4cm = annually
