2- aortic disease: aneurysm & dissection Flashcards
what is an aneurysm?
a permanent, localised dilatation of an artery of more than 50% of the normal arterial diameter (i.e. 50% increase in diameter compared with non dilated adjacent vessel)
what is normal aortic diameter?
1.2 - 2 cm
what is a true aneurysm?
where all the 3 layers of the artery are involved
what is a false aneurysm?
where there is a defect in the wall of the artery and it is the surrounding structures (skin, fat, fascia) that keep the aneurysm restrained
what is the pathogenesis of abdominal aortic aneurysm?
- related to medial degeneration (tunica media degeneration)
- abnormal regulation of elastin & collagen proteins in the aortic wall by enzymatic agents such as metallo-proteinases not working properly causing a disruption →aneurysmal dilation (abnormal widening & bulging) →increase in aortic wall stress (more pressure & stretching)
- this continues and makes progressive aneurysmal dilation (process continues to worsen over time)
does atherosclerosis related to aneurysmal formation?
no, not directly related - just an incidental finding
what does abdominal aortic aneurysm present like?
- 75% of all are asymptomatic until rupture occurs
- 35% are symptomatic
- with sudden onset of abdominal & back pain and/or collapse
*often identified on imaging for other pathology
what are ultrasound limitations?
only gives size - not moving up or show if just about to rupture
what happens in CT angiography?
inject contrast and wait for contrast to hit arteries, you can then CT all the way down →allows us to see shape, size, what vessels involved, allows you to plan treatment
- IV contrast
- scan when contrast is in arterial system
- aneurysm morphology
what are most ruptured aneurysms still contained in?
the retroperitoneum
when is it recommended to repair a asymptomatic abdominal aortic aneurysm?
when it reaches 5.5 cm AP (anteroposterior) diameter
what is criteria for aneurysm intervention?
- reaches 5.5 cm
- undergoes rapid expansion >1cm per year
- when AAA is symptomatic
- rupture = if AAA bursts then life threatening emergency
- thrashing = unstable or rapidly changing characteristics of AAA
- pain
what is elective aneurysm repair?
scheduled intervention for an abdominal aortic aneurysm (AAA) that is performed in a non-emergency setting
= it’s a prophylactic operation to reduce the risk of rupture balanced against risk of procedure
what is emergency aneurysm repair?
therapeutic procedure balancing expectation for death against risk of procedure
what is therapeutic procedure?
aimed at improving or treating a medical condition
what is prophylactic procedure?
aimed at preventing medical condition
what is EVAR?
endovascular aneurysm repair
= type of repair within blood vessel using minimally invasive techniques, via percutaneous access in groin with the stent inserted up through the common femoral artery
- stent-graft reinforces weakened or bulging area of aorta
what are positives & negatives of EVAR?
positives = less mortality risk (far safer in complex aneurysms), much faster recovery
negatives = not possible in 25% of patients, needs on going follow up, may need further investigations
what is open repair?
type of repair of aortic aneurysm through direct surgical intervention where weakened/bulging area assessed and repaired through direct surgical intervention, sewing graft to replace removed section of aorta
what are positives and negatives of open repair?
positives = possible in just about everyone, rare further investigations, known to be effective for life
negatives = greater mortality risk, much slower recovery
what assessments should be carried out to assess fitness for AAA intervention?
- cardiac assessment - echo/ejection fraction
- respiratory assessment - PFT
- cardiopulmonary exercise test - CPX testing
- renal assesment - U&Es
- vascular assessment - peripheral pulses/ABPI
- anaesthetic assessment
- EBT - end of bed or eyeball test
what is some criteria of the aorta & vessels to be able to do an EVAR?
Aorta above AAA needs to be of correct morphology (size/shape) to land the stent above the AAA and the iliac arteries need to be disease free to be able to insert the device up to the AAA
= this needs imaging & contrast to check
how many elective AAA can be treated with EVAR?
60-70% of elective AAA can be treated with EVAR
*saying that most scheduled aneurysm repairs can be treated with EVAR
what is the outcome of a ruptured AAA?
- 50 - 75% will of patients not make it to hospital
- Most ruptured AAA are retroperitoneal, contained rupture
- Free intra-peritoneal rupture is rapidly fatal
- 50% operative mortality
what is operative mortality for
a) elective open AAA?
b) elective EVAR?
a) 3-4%
b) 1-2%
what are complications for open repair?
- MI, CVA
- pneumonia, wound infection, UTI, graft infection
- DVT /PE
- renal failure - dialysis may be required
- Mesenteric ischaemia – may require bowel resection
- Lower Limb Ischaemia + ‘Trash’ foot
- Erectile dysfunction
- Death
what are complications of EVAR?
- Stent misplacement – covering the renal arteries, internal iliac arteries
- Endoleak (this is defined a blood flow out with the stent in the aneurysm sac)
- Stent migration and stent dislocation (the stents are modular and inserted into one another and over time they may dislocate from one another)
- All EVAR require lifelong follow up (~20% of EVAR patients will require further intervention over their lifetime)
what is the screening programme for aneurysms?
it aims to offer screening to all males >65 years with ultrasound scan (suggests reducing risk of death by 50%)
what is aortic dissection?
dissection is tear - so it’s an aortic tear
(it’s a distinct separate thing from aortic aneurysm but a dissected aorta may become aneurysmal)
what is acute aortic syndrome?
group of series & potentially life-threatening conditions affecting aorta
what are types of acute aortic syndrome?
- penetrating aortic ulcer = ulcer or lesion that penetrates through inner layers of aortic wall
- intramural haematoma = collection of blood within the layers of aortic wall without a clear tear or dissection
- aortic dissection = condition where there is a tear in inner layers of the aorta, allowing blood to flow between the layers, potentially causing layers to separate
what do all the types of acute aortic syndrome have in common?
- all have disruption to tunica media layer
- all have bleeding between the layers
- all have transmural bleeding which is bleeding that extends through all layers potentially leading to rupture, outwith adventitia
why is it tricky to deal with acute aortic syndrome?
because since all types have disruption to tunica media it’s tricky to fix - think like toilet paper in a packet (inside cardboard ring is intima, paper itself is media and outer plastic is adventitia), the paper gets all soggy and hard to fix
what are some factors associated with acute aortic syndrome?
- Family history
- specific Gene mutations (fibrillin-1, transforming growth factor β1 etc) can affect structure & function of aorta
- Connective Tissue Disorders, this can impact integrity of aorta
- Ehlers Danlos, Marfans, Loeys dietz
- Trauma including iatrogenic
what happens in formation of aortic dissection?
cystic medial necrosis & medial degeneration →tear intimal layers →blood propagates within medial layer creating separation of layers →creates a flap; true lumen & false lumen
where can the tear (aortic dissection) propagate? (spread)
centrally: aortic arch & it’s branches, aortic valve, coronary arteries
distally: mesenteric/renal arteries, iliac arteries down the limb
how do you classify aortic dissection?
Stanford guide
Type A = involves ascending aorta & arch, cardiothoracic emergency
Type B = involves descending thoracic aorta (distal to left subclavian), vascular surgery
how do people present with aortic dissection?
excruciating chest or interscapular pain (also back pain, and sometimes abdominal pain)
what can propagation of dissection flap lead to?
- if involves valve →disrupted function →Acute aortic valve regurgitation
- if affects coronary arteries →Myocardial infarction
- if flap extends into pericardial sac →Cardiac tamponade
- if involves blood vessels to brain →Stroke
- if spread to vessels of upper limb →Upper limb ischaemia
- Lower ischaemia
- if involves blood vessels supplying intestine →Mesenteric ischaemia
- if spread to spinal cord →Spinal ischaemia (paraplegia)
what does CT angiogram of aortic dissection allow?
would be from aortic arch to femorals
- Delineates (portrays precisely) anatomy
- Delineates perfusion to end organs
- Allows surgical planning (if appropriate)
what is the aim of treatment of aortic dissection?
- prevent progression of dissection
- prevent rupture
- maintain or restore perfusion to end organs
*you want to lower blood pressure & operate if needed
what intervention do you want to do for acute phase aortic dissection?
acute phase < 2 weeks
= aim to reduce flow in false lumen thereby decreasing diameter expansion of dissection
- false lumen remodelling
- complicated type B dissection
(high risk, tissues like soggy paper)
what intervention do you want to do for sub acute phase aortic dissection?
sub acute = 2 weeks to 90 days
(tissues more robust)
- false lumen modelling
- reduce aortic related complications (aneurysms etc)
*jury’s still out on whether to operate
what are complications of intervention?
- 30 day mortality up to 30% - 40%
- Stroke – up to 10%
- Spinal cord ischaemia – 2%
- Retrograde Type A dissection - extension of dissection backward into ascending aorta
