Abdominal Aortic Aneurysm Flashcards
1
Q
What is the definition of an aneurysm?
A
an aneurysm is an artery that has a localised dilation
with a permanent diameter of at least 1.5x the expected diameter of that particular artery
an aneursym can be a true aneurysm or a false aneurysm
2
Q
What is a true aneurysm?
Which arteries tend to be affected by this?
A
the wall of the artery forms the wall of the aneurysm
the arteries most frequently involved are:
- abdominal aorta (most common)
- iliac artery
- popliteal artery
- femoral artery
- thoracic aorta (least common)
3
Q
What is a false aneurysm (pseudoaneurysm)?
Which artery is most commonly affected?
A
other surrounding tissues form the wall of the aneurysm
this most commonly occurs in the femoral artery following puncture
if there is inadequate pressure applied to the puncture site, blood spills out and forms a haematoma
eventually the surrounding soft tissue will form the wall of the haematoma
4
Q
What is the difference between a pseudoaneurysm and a true haematoma?
A
pseudoaneurysm:
- there is still communication between the lumen of the artery and the fluid collection
true haematoma:
- there is either no communication
- or there is a one way “leakage” of fluid
5
Q
What are the 2 different shapes of aneurysm?
A
fusiform:
- the aneurysm is tapered at both ends (like a raindrop with 2 points)
sac-like:
- the aneurysm is more rounded in shape
6
Q
When inspecting an aneurysm, what characteristic should you feel for?
How is this different to nodes overlying an artery?
A
you should feel for the aneurysm being EXPANSILE
this means that it expands and contracts
nodes overlying arteries are PULSATILE
these means they do not expand and contract, but just transmit the pulse
7
Q
What are the risk factors for aneurysmal disease?
What condition are these similar to?
A
the risk factors for aneurysmal disease are similar to those for atheromatous disease, despite the different pathology
- hypertension
- smoking
- obesity
- diabetes
- sedentary lifestyle
- high LDL levels
- increasing age
- family history
- 10% of cases have a first-order relative also with the condition
8
Q
What are specific aetiological factors for aneurysmal disease?
A
- coarctation of the aorta
- pregnancy (especially in the 3rd trimester)
- Marfan syndrome (or other connective tissue disorders)
- previous aortic surgery
- trauma
9
Q
Who is more commonly affected by aneurysms?
A
- incidence increases with age
- 5% of men over 60 have an aneurysm
- aneurysms are 3-5 x more common in men than women
10
Q
What are the common complications of local aneurysms?
A
Aneurysms themselves do not often constitute a primary problem
- can cause local obstruction (e.g. of the IVC)
- can cause impaired blood flow to the lower limbs
They are a risk factor for thrombosis and embolism
11
Q
What is the main risk factor associated with aneurysms?
A
the tendency of aneurysms to dissect and rupture
an aortic aneurysm most commonly ruptures into the retroperitoneal space
12
Q
How does repair of aneurysms differ before and after rupture?
A
- elective repair of aneurysms before rupture is comparitively safe
- repair of aneurysms after rupture has a very high mortality
13
Q
How are aortic aneurysms usually detected?
A
They are usually asymptomatic and are identified incidentally
e.g. through examination, AXR, CT or USS
14
Q
What is the mean age of presentation for an aortic aneurysm?
How are they usually picked up?
A
65
around 65% of aneurysms are sufficiently calcified to be picked up on abdominal X-ray
15
Q
A
16
Q
What method is used to stage aneurysms?
A
ultrasound scan
it is accurate at assessing the site of the aneurysm and easy to follow up cases to assess development
17
Q
What are the benefits of using CT to investigate aneurysms?
Why is CT not used to assess and follow up aneurysms?
A
- more accurate than USS
- useful at looking at surrounding structures (e.g. to see if there is any compression
it is very expensive so only tends to be used pre-operative assessment
18
Q
What is risk of dissection of an aneurysm correlated with?
A
risk of dissection (bursting) increases with the diameter of the aneurysm
19
Q
What is the main concern about thrombus formation and aneurysms?
A
aneurysm is a source of thrombus formation, which can emobilise to the lower limbs
very rarely does the site of the aneurysm become completely occluded by thrombus
20
Q
What do NICE guidelines state about which aneurysms need surgical intervention?
A
an aortic aneurysm of greater than 5.5cm in diameter should be treated
below this size, the risk of dissection (bursting) is outweighed by the risk of surgery
21
Q
What is the annual risk of rupture of aortic aneurysms with a diameter of 5.5, 6.5 and 7cm?
A
- at 5.5cm annual risk of rupture is 25%
- at 6.5cm annual risk of rupture is 35%
- at >7cm annual risk of rupture is 75%
22
Q
Other than diameter >5.5cm what are other indications for treatment of aneurysms?
A
- symptomatic aneurysms of smaller size are sometimes operated on
- pain is thought to be a risk factor for rupture
- thrombo-embolus is an indication for surgery
23
Q
What is the surgical procedure that is performed to treat an aortic aneurysm?
A
open laparotomy
the affected segment of aorta is clamped and replaced by a prosthetic segment (usually a Dacron graft)
(or the affected artery segment may be bypassed )
24
Q
What are the potential complications following open laparotomy to treat an aortic aneurysm?
A
graft failure is rare and complications are also rare
- kidney problems
- paraplegia
- ischaemic colitis
- fistula formation with the small bowel
infection is also very rare
25
How does mortality change in elective aneurysm, symptomatic aneurysm and ruptured aneurysm surgery?
* 5-8% in elective asymptomatic AAA
* 10-20% in symptomatic emergency AAA
* 50% in ruptured AAA
long-term survival for most patients with AAA is almost identical to the general population
26
What is an alternative surgical option to open laparotomy for treating aortic aneurysm?
**Endoluminal surgery - *Endovascular aneurysm repair (EVAR)***
* an aortic graft is inserted through the femoral artery and passed up into the abdominal aorta
* this method is preferred due to its lower mortality
27
Why is endovascular aneurysm repair (EVAR) not performed in all patients?
many patients are not suitable for this method
there must be **_at least 2.5cm of normal aorta between the aneurysm and the renal arteries_** to securely fix the graft in place
28
What are the benefits and drawbacks of performing EVAR compared to open laparotomy to fix an aortic aneurysm?
**benefits:**
* lower mortality of 1.2%
* risks of procedure are much lower
**drawbacks:**
* higher risks of complications with the graft
* graft can fail or can be moved, allowing blood to refill the aneurysm
29
How does death rate change with age if an aortic aneurysm was to rupture?
death rate from rupture of an aortic aneurysm increases with age
* age 55-59 - death rate is 12.5 per 100,000
* age 80+ - death rate is 273 per 100,000
30
Of those with a ruptured aortic aneurysm, what % tend to survive?
* \>75% with a ruptured AA will die - usually before getting to hospital
* of those that reach hospital, surgery has a 50% mortality rate
* only **around 10%** of those with a ruptured AA will survive
31
What is meant by "rupture" when talking about aortic aneurysms?
rupture describes the **wall of the aorta completely failing**, and **blood escaping into a body cavity** (e.g. abdominal cavity)
this is different to dissection, although dissection often leads to rupture
32
33
What is meant by "dissection" when talking about an aortic aneurysm?
where blood escapes through the innermost layer of the wall of the aorta, and **prises apart the media**, creating a **new lumen**
this can be stable but also has a high risk of rupturing
34
What is meant by a "double-barreled aorta"?
an aorta with a second vascular lumen formed in the media of the aortic wall, which connects the proximal and distal intimal tears in an aorta with a dissecting aneurysm
this occurs when the new lumen is absorbed back into the main lumen
35
What happens if an aortic aneurysm dissection tracks back?
the dissection is sometimes able to track back all the way to the pericardium and cause **haemopericardium**
36
How urgent is aortic aneurysm dissection and why?
it is a medical emergency and needs to be treated ASAP
if blood manages to escape through all the layers of the aortic wall, then **_rupture_** is the result
37
What is the difference between an acute and chronic aortic dissection?
**Acute:**
* the intimal tear is diagnosed at 14 days or less
**Chronic:**
* the intimal tear is diagnosed after 14 days or more
38
What is the difference between an anterograde or retrograde dissection?
aortic dissections from the initial intimal tear can progress distally, proximally, or in both directions from the point or origin
**anterograde dissections:**
* propagate towards the iliac arteries
**retrograde dissections:**
* propagate towards the aortic valve (at the root of the aorta)
39
What are additional risks associated with retrograde aortic aneurysm dissections?
they can result in:
* prolapse of the aortic valve
* bleeding into the pericardium
* cardiac tamponade
40
How is the Stanford classification used to classify aortic dissections?
**_Type A:_**
* involves the ***ascending aorta***
* may propagate to the aortic arch and descending aorta
* tear can originate anywhere along this path
**_Type B:_**
* dissections affect the ***_descending aorta ONLY_***
* do not involve the ascending aorta
41
How is the DeBakey classification used to group aortic dissections anatomically?
**_Type I:_**
* originates in the ascending aorta and propagates at least to the aortic arch
**_Type II:_**
* confined to the ascending aorta
**_Type III:_**
* originates distal to the subclavian artery in the descending aorta
42
How can a type III DeBakey aortic dissection be further classified?
**_Type IIIa:_**
* originates distal to the subclavian artery in descending aorta
* extends ***_distally to the diaphragm_***
**_Type IIIb:_**
* originates distally to the subclavian artery in descending aorta
* extends ***_beyond the diaphragm into the abdominal aorta_***
43
How does an aortic dissection present with pain?
How does the pain differ in a dissection of the ascending aorta/descending aorta?
there is **sudden onset**, **severe pain**
it is often described as **tearing** and usually **radiates to the back**
in the ascending aorta, pain is often in the chest
in the descending aorta, pain is often in the back
44
What are the other symptoms, other than pain, that are associated with aortic dissection?
* collapse due to hypotension
* expansile (not pulsatile) mass in the abdomen
* shock
* hypotension
* tachycardia
* profound anaemia
* sudden death
45
What are the most common clinical signs of aortic dissection?
the most common clinical signs include:
* tachycardia
* hypotension
* new aortic regurgitation murmur
* signs of end-organ hypoperfusion
46
What are signs of end-organ hypoperfusion that may be present as a clinical sign of aortic dissection?
* reduced urine output
* paraplegia
* lower limb ischaemia
* abdominal pain secondary to ischaemia
* deterorating conscious level
47
Why is hypotension a clinical sign of aortic dissection?
it occurs secondary to hypovolaemia from blood loss into the dissection
or cardiogenic from severe aortic regurgitation or pericardial tamponade
48
What is the characteristic presentation of aortic dissection?
**a tearing chest pain, classically radiating through to the back**
the diagnosis is often challenging and may be a more subtle presentation
49
What are the differential diagnoses for aortic dissection?
* myocardial infarction
* pulmonary embolism
* pericarditis
* musculoskeletal back pain
50
How can presentation of aortic dissection and MI be distinguished?
MI presents with a classically **_crushing and central chest pain_**
there are signs of **ischaemia on ECG**
and / or **raised serum troponin levels**
51
How can aortic dissection be clinically distinguished with pulmonary embolism?
* **dyspnoea** is a prominent feature
* ABG will demonstrate **hypoxia**
* this is confirmed with **CTPA** (pulmonary angiogram) or **V/Q scan**
52
How can aortic dissection be distinguished clinically from pericarditis?
pericarditis classically presents with **_pleuritic chest pain_**
an ECG will show **diffuse ST elevation**
as well as potential **pericardial rub** on auscultation
53
How can aortic dissection be distinguished from 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
54
What are your initial investigations for aortic dissection?
diagnosis is usually clinical, and needs to be made quickly
* **baseline blood tests** with a **crossmatch** of at least 4 units
* FBC, U&Es, LFTs, troponin, coagulation
* **arterial blood gas**
* **ECG** to exclude any cardiac pathology
55
What is the imaging of choice that is recommended to diagnose aortic dissection?
**CT angiogram**
this allows for classification, establishing the anatomy of the dissection and assists surgical planning
56
What is the initial management for aortic dissection, regardless of what type it is?
urgent initial assessment is required, as for any other critically ill surgical patient
* start **high flow oxygen**
* gain **IV access** with **2x large bore cannulas**
* **fluid resuscitation** (should be done cautiously)
57
What is the target pressure for fluid resuscitation in a rupture and an uncomplicated dissection?
**_Rupture:_**
* target pressure sufficient for ***cerebral perfusion only***
**_Uncomplicated dissection:_**
* target systolic pressure should be kept ***below 110mmHg***
58
What is the main difference in the initial management of Type A and Type B Stanford dissections?
**_Type A:_**
* should be managed ***surgically*** in the first instance
* carry a ***worse prognosis*** than Type B
**_Type B:_**
* any uncomplicated Type B dissections can usually be ***managed medically***
59
What treatment / imaging do all patients who have had an aortic dissection require in the future?
* all patients require **_lifelong antihypertensive therapy_** & **surveillance imaging**
* imaging occurs at 1, 3 and 12 months post-discharge
* then further scans at 6-12 month intervals thereafter depending on the size of the aorta
60
What surgical technique is used to treat Type A aortic dissections?
**Dacron graft**
* the ascending aorta (with or without arch) is removed & replaced with a synthetic graft
* if dissection has damaged the suspensory apparatus of the aortic valve, this will also require repair
61
What is the first line medical treatment for management of Type B dissections?
What is the aim of this therapy?
* management of hypertension with **_IV beta blockers (labetalol)_**
* calcium channel blockers are used as second line therapy
the aim is to **rapidly lower systolic pressure, pulse pressure** and **pulse rate**
this will ***minimise stress of the dissection*** and ***limit further propagation***
62
Why is medical management the gold standard for treatment of Type B dissections?
in the acute setting, endovascular repair is not recommended due to the **risk of retrograde dissection**
63
When is surgical intervention of Type B dissections warranted?
only in the presence of certain complications, such as:
* rupture
* renal, visceral or limb ischaemia
* refectory pain
* uncontrollable hypertension
64
What happens if a Type B dissection develops to become chronic?
What is the treatment then?
if it is chronic, there is continued leakage into the dissection, even if a stent has been placed
the most common complication of chronic disease is formation of an **aneurysm**
then **endovascular repair** will offer a better survival chance
65
What are the possible complications of aortic dissection?
complications depend on the **site and spread of the dissection into the aortic branches**, damaging end organs
* aortic rupture
* aortic regurgitation
* myocardial ischaemia
* secondary to coronary artery dissection
* cardiac tamponade
* stroke or paraplegia
* secondary to cerebral artery or spinal artery involvement
66
Which segment of the aorta is usually implicated in an abdominal aortic aneurysm?
80% of cases found in the **_infrarenal segment_** of the aorta
these most commonly occur **below the level of the renal artery**
67
How is the pain described in an abdominal aortic aneurysm?
What can it be confused with?
* rapid expansion or rupture causes **_epigastric pain that radiates to the back_**
* pain may be present in the **groin, iliac fossae and testicles**
* pain can be **constant or intermittent**
**_DO NOT DISMISS AS RENAL COLIC_**
68
How does a thoracic aortic aneurysm tend to present?
* asymmetrical brachial / radial / carotid pulses if dissection involves aortic arch
* **BP may be different in each arm**
69
What is the definition of an aneurysm?
What is the most common cause of a true aneurysm?
**_permanent dilation of the vessel wall_**
the fact that it is permanent implies that the vessel wall itself is altered in some way
**_atheromatous degeneration_** is the most common cause of true aneurysm
70
What are the risk factors for aneurysm?
as the most common cause is atheromatous degeneration, the risk factors are the **same as for CHD**
* smoking
* family history
* diabetes
* hypertension
* advancing age
* hyperlipidaemia
71
What is thought to be the pathology underlying an aneurysm?
* **ischaemia of the aortic media** where there is an atherosclerotic plaque
* this is a result of **macrophage enzymes** (released when macrophages are activated) that **break down elastic fibres** (collagen & elastin)
* ischaemia results in **loss of the normal elastic nature** of the media, allowing it to **expand**
72
What is thought to explain the familial aspect of aneurysms?
there is evidence that various genetic variants of collagen are more susceptible to breakdown by macrophages
73
What is Marfan syndrome?
What mutation causes it?
a connective tissue disorder that is usually inherited in an autosomal dominant manner
it is caused by **_mutations in the FBN1 gene_**, which provides instructions for making the **_fibrillin-1 protein_**
74
How many people and what gender are affected by Marfan syndrome?
* very common affecting 1 in 5000 individuals
* 25% of cases are due to a new mutation
* males and females are equally affected
75
What is tested for when screening family members for Marfan syndrome?
**Fibrillin-1 gene mutations**
These are seen in 80% of cases
76
What are the most common clinical features of Marfan syndrome?
* arachnodactyly
* joint hypermobility
* scoliosis (lateral curvature of the spine)
* dislocation of the lens of the eye
* high arched palate
* chest deformity
* patients are usually tall and thin, with long limbs
77
What is arachnodactyly?
**abnormally long and thin fingers** in comparison to the palm
in Marfan syndrome, the fingers may be bent backwards at the MCP joint to 180 degrees
78
How can Marfan syndrome predispose to aneurysms?
Which part of the aorta tends to be affected?
* **weakening of the media layer** of the aorta, leading to **dilatation**
* dilatation typically occurs in the **_ascending aorta_**
* there may also be **heart valve defects** (e.g. aortic regurgitation) which complicate the issue
* the **_root of the aorta_** tends to be affected
79
How can Marfan syndrome also lead to lung and dura disorders?
as well as fibrin defects, there are problems in the **TGF-B (transforming-growth-factor-B)**
this accumulates in the heart valves and blood vessels and **alters their underlying structure**, leading to complications
80
What medical therapy is used in Marfan syndrome?
**B-blockers**
proven to reduce the rate and risk of dilatation of the aorta
81
How is monitoring carried out in patients with Marfan syndrome?
**monitoring of aortic dilatation** through X-ray, Echo, MRI or CT
patients are usually followed up with **yearly Echo** to assess the **size of the aorta**
in some cases, elective replacement of the ascending aorta may be recommended to prevent dissection, but has a mortality of 5-10%
82
What activities should patients with Marfan syndrome avoid?
endurance sport / activities
83
What measures are in place to monitor pregnant women with Marfan syndrome?
When is caesarean section recommended?
both pregnancy and Marfan syndrome are risk factors for AA so the aorta is monitored by an **_Echo every 6 weeks_**
caesarean is considered when **aortic root is \>4cm**
B-blocker therapy is safe to continue
84
What is the overall prognosis like in Marfan syndrome?
generally good, although less than the general population
surgical interventions have increased average life expectancy by 13 years
