Abdominal aortic aneurysm Flashcards
Average lifetime aortic blood flow
200 million litres
Layers of arterial wall
Tunica intima: covered by endothelium
Tunica media: thick collagen
Tunica adevntita: extrnal coverings containing vasa vasorum
Windkessel function
Refers to the secondary pump quality of the aortic
Elastic nature provides pump force during diastole
–> helps to perfuse coronaries
Average aortic expansion
Men: 0.9mm per DECADE
Women: 0.7mm per DECADE
Symptoms of aortic disease
Acute deep, aching or throbbing chest or abdominal pain that can spread to the back, buttocks, groin or legs, suggestive of AD or other AAS, and best described as ‘feeling of rupture’
Cough, shortness of breath, or difficult or painful swallowing in large TAAs.
Constant or intermittent abdominal pain or discomfort, a pulsating feeling in the abdomen, or feeling of fullnessafter minimal food intake in large AAAs.
Stroke, transient ischaemic attack, or claudication secondary to aortic atherosclerosis.
Hoarseness due to left laryngeal nerve palsy in rapidly progressing lesions.
Ideal place to measure diameter of aorta
Measure diameter perpendicular to flow
Measure at set anatomical points
When in cardiac cycle to measure aortic diameter
Discussion to be had
Diastolic measurements are the most reproducible
Inter and itnra variability in measurement of diameter on CT
Inter assessor variability ~ 5mm
Intra assessor variability ~3mm
Generally changes <5mm unlikely to be significant
Ultrasound measurement of aortic diameter
Tend to under report size by 1-3mm
Measured in AP direction
Use of PET CT
18F-fluorodeoxyglucose (FDG), which is taken up with high affinity by hypermetabolic cells (e.g. inflammatory
cells), and can be used to detect vascular inflammation in large vessels.
The advantages of PET may be combined with CT imaging with good resolution.
inflammatory vascular disease (e.g. Takayasu arteritis,GCA), to detect endovascular graft infection,
and to track inflammatory activity over a given period of
treatment
Disadvantages of MRA
Cannot evaluate calcification which is important for evaluating landing zones of a graft
Availability
Difficulty in patient monitoring during scan
Time taken to perform scan
Gadolinium causes nephrogenic systemic fibrosis
Measuring aortic stiffness
Carotid -femoral pulse wave velocity
Fast velocity = stiffer aorta
> 10m/s = stiff aorta
Predictor of CV events and poor otucome
Effect of smoking on aneurysm expansion
Quicker aneurysm expansion
Smoking status associated with expansion rate of 0.4mm / YEAR
TEVAR landing zone
Diameter <40mm
Length >20mm
CT angiogram pre TEVAR
<3mm slices
From supra-aortic vessels down to femoral arteries
Asses landing zones
Asses relationship to side branches
Evaluate femoral access
Stent sizing in dissection vs aneurysm TEVAR
Dissection:
- Land at site of false lumen to occlude lumen and de-pressurise false lumen
- Do not over-size in diameter
Aneurysm
- Over-size in diameter by 10-15%
- Landing zone needs to be clear of aneurysmal disease
Definition of proximal aortic neck
Segment of aorta below renal arteries up to the most cephalic section of aneurysm
Hostile neck
>60% angulation –> migration and endoleaks
<15mm –> difficult landing
>32mm in diameter means endovascular stent unlikely
Features of good proximal aortic neck
<60% angulation
> 10-15mm in length
<32mm in diameter
Why do you not cover both internal iliacs
Causes bilateral hypogastric artery occlusion
Leads to:
- Impotence
- Spinal cord ischaemia
- Visceral ischaemia
- Buttock caludication
When to ligate inferior mesenteric artery (open)
Conditions for ligation:
- brisk back bleeding from IMA
- bilateral patent hypogastric arteries i.e. not occluding either internal iliac
If sluggish bleeding or occluding one of the iliac –> re-implant IMA
Definition of acute thoracic aortic syndrome
Defined as emergency conditions with similar clinical characteristics involving the aorta
Essentially a breakdown of the intima and media:
- intramural thrombus
- penetrating atherosclerotic ulcer
- dissection
- rupture
De Bakey classification
De Bakey = 1, 2 , 3
Classification of throacic aortic dissection
1: ascending and descending thoracic aorta
2: ascending thoracic aorta prior to innominate artery
3: descending thoracic artery at point of innominate artery
Stanford classification
A or B
A: involved the ascending thoracic aorta +/- descending thoracic aorta
B: involves only the descending thoracic aorta
Classification of aortic dissection
1 - 5
1: classic dissection. No communication between to lamina, true and false lumen exist
2: intramural haematoma
3: subtle dissection with bulging of arterial wall
4: penetrating atherosclerotic ulcer
5: traumatic / iatrogenic
Recommendations for imaging of aorta (7)
1) It is recommended that diameters be measured at pre-specified anatomical landmarks, perpendicular to the longitudinal axis. IC
2) In the case of repetitive imaging of the aorta over time, to assess change in diameter, it is recommended that the imaging modality with the lowest iatrogenic risk be used. IC
3) In the case of repetitive imaging of the aorta over time to assess change in diameter, it is recommended that the same imaging modality be used, with a similar method of measurement. IC
4) It is recommended that all relevant aortic diameters and abnormalities be reported according to the aortic segmentation. IC
5) It is recommended that renal function, pregnancy, and history of allergy to contrast media be assessed, in order to select the optimal imaging modality of the aorta with minimal radiation exposure, except for emergency cases. IC
6) The risk of radiation exposure should be assessed, especially in younger adults and in those undergoing repetitive imaging. IIaB
7) Aortic diameters may be indexed to the body surface area, especially for the outliers in body size. IIbB
Recommendations for thoracic endovascular repair (TEVAR) (4)
1) It is recommended that the indication for TEVAR or EVAR be decided on an individual basis, according to anatomy, pathology, comorbidity and anticipated durability, of any repair, using a multidisciplinary approach. IC
2) A sufficient proximal and distal landing zone of at least 2 cm is recommended for the safe deployment and durable fixation of TEVAR. IC
3) During stent graft placement, invasive blood pressure monitoring and control (either pharmacologically or by rapid pacing) is recommended. IC
4) Preventive cerebrospinal fluid (CSF) drainage should be considered in high-risk patients. IIaC
Recommendations for surgical repair of thoracic aorta
Cerebrospinal fluid drainage is recommended in surgery of the thoraco-abdominal aorta, to reduce the risk of paraplegia. IB
Aortic valve repair, using the re-implantation technique or remodelling with aortic annuloplasty, is recommended in young patients with aortic root dilation and tricuspid aortic valves. IC
For repair of acute Type A AD, an open distal anastomotic technique avoiding aortic clamping (hemiarch/complete arch) is recommended. IC
In patients with connective tissue disordersd requiring aortic surgery, the replacement of aortic sinuses is indicated. IC
Selective antegrade cerebral perfusion should be considered in aortic arch surgery, to reduce the risk of stroke. IIaB
The axillary artery should be considered as first choice for cannulation for surgery of the aortic arch and in aortic dissection. IIaC
Left heart bypass should be considered during repair of the descending aorta or the thoraco-abdominal aorta, to ensure distal organ perfusion. IIaC
