00:01
So who gets abdominal
aortic aneurysm?
So we have aneurysms that are going
to affect various parts of the aorta
from the ascending aorta,
the thoracic aorta,
descending aorta,
and infrarenal abdominal aorta.
00:14
So this is abdominal
aortic aneurysm or AAA,
much more common in
men than in women,
much more common in smokers.
00:23
So smoking probably has
some effect on activating
the inflammatory cells
that give rise to AAA.
00:31
The incidence is about 3% in
individuals who are 65-75 years old,
so it's reasonably common.
00:38
In fact, if you do a careful exam
on your geriatric population,
you will find this
not infrequently.
00:46
The incidence goes up and the
incidence is shifted to younger years.
00:52
It's people who are smokers, so 4.3% of
smokers who are a decade or so younger.
00:59
Atherosclerosis is
probably the initial
driving force for
abdominal aortic aneurysms.
01:04
But it's also the nature
of the inflammatory cells
and what they're making that
is breaking down elastic tissue
and causing defective
collagen synthesis.
01:13
Abdominal aortic aneurysms typically
occur in the infrarenal aorta,
that's actually because there is an
additional component of turbulence.
01:22
So the same factors
overall causing
atherosclerosis everywhere
within the aorta.
01:27
But in the infrarenal
aorta kind of there,
and into the iliac bifurcations,
there's greater turbulence
because we have blood coming
and then hitting
that bifurcation.
01:37
So in that zone is where
we tend to see the worst
atherosclerosis in the aorta,
but also where the abdominal
aortic aneurysms occur.
01:46
Here's an example.
01:47
So we have on the left
hand side an aorta,
near the top of the picture
would be the patient's chest,
and ultimately,
their head towards the bottom
is the bifurcation of
the iliacs into the legs.
01:59
And you see in the region below
the level of the renal arteries,
there is a somewhat
dilated fusiform aneurysm
that here is filled up with
blood at higher magnification.
02:11
Why is that happening?
Well, that's happening because we have
an abnormal flow in this location.
02:16
We have weakened the
wall, it's dilated.
02:19
And now we have that bifurcation
too, where we have turbulence,
a combination of the dilated
wall, abnormal flow,
turbulence is going to
give us thrombus formation.
02:29
So that can also be
a cause of occlusion
of the vasculature
in that location.
02:36
This is just giving you a sense
of this on an angiography CT.
02:40
So the contrast
material is bright white
and the arrow is pointing
to the abdominal aorta.
02:48
The area that is bright
white is the lumen.
02:51
So that is the contrast
material within the lumen
but you see a slight you
see a darker region of grey,
above and to the left
of that brightness
that represents the actual outline
of the aorta because it's dilated,
but now that has been
filled in with a blood clot.
03:12
So there is no contrast
material in there.
03:14
That's blood clot in a
dilated aortic aneurysm.
03:20
Other causes of abdominal
aortic aneurysms
rarely 5-10% of the time
are inflammatory aneurysms.
03:27
This is much more
driven by inflammation,
and typically occurs in a much
younger patient population.
03:37
Patients with inflammatory aneurysms tend
to have elevated inflammatory markers,
and may present with relatively
acute onset of back pain.
03:47
There is also immunoglobulin
G4/ IgG4-related aortic disease,
and this is associated with
high plasma levels of IgG4
and high levels of plasma
cells expressing IgG4
within tissue fibrosis
around the aorta.
04:03
This can affect not
only the abdominal aorta
but other areas within the aorta
and also can affect the pancreas,
the biliary system,
salivary glands amongst others.
04:14
So IgG4-related
disease is a different,
an interesting entity that
is discussed in other talks.
04:20
If you want to scan around
on the Lecturio site,
you can find it because
I talked about it.
04:26
Then there's mycotic aneurysms.
04:28
These are lesions that are infected
by circulating microorganisms
that have gone in through
the vasa vasorum
and have now caused local destruction of
the wall leading to aneurysm formation.
04:40
Signs, symptoms,
and complications.
04:42
So again, this is showing you a
reconstruction of an angiography study
where we have an abdominal
aortic aneurysm that's indicated
by the white box and it's
below the renal arteries
above the bifurcation
of the aorta.
04:56
That's the classic location.
04:58
This patient also has aneurysms that
involve the smaller iliac arteries.
05:03
Those are very dilated,
they're not the normal calibre.
05:08
Commonly, AAAs are asymptomatic.
05:12
That's why you have to
do a very careful exam
on your geriatric population
to actually find them.
05:17
But if they're going to be symptomatic
the kinds of symptoms that they will have
is that you can
have frank rupture.
05:23
These things can get big enough,
and the walls can become defective enough,
thin enough that you
actually formally rupture.
05:30
It usually leads to exsanguination
with hemoperitoneum.
05:34
You can have obstruction of
vessels branching off the aorta
as a result of the dilation,
the expansion and superimposed thrombosis.
05:44
In that thrombosis, you can also
have things that fragment often
embolize into the distal
extremities, for example.
05:52
You can get compression of the ureters
so that you get (hydro)nephrosis of the kidneys
or you can even erode into the
vertebrae as this pulsatile mass
expands and expands and expands and
rubs up against the vertebral bodies.
06:07
The risk of rupture, when aneurysms
are less than 5 cm is 1% per year.
06:13
Even so, that 5% limit is where we
will do either a surgical intervention
or we will do put in
intravascular stents
to keep the aneurysm from expanding
and potentially rupturing.
06:27
The risk of rupture is greater
than 10% if it gets to 5-6 cm.
06:32
And if it gets larger than 6 cm,
1 out of 4 patients will
have a rupture each year.
06:39
That's pretty substantial.
06:40
And when patients rupture, a AAA, they
usually die as a result of exsanguination.
06:48
Alright, that's AAA's,
which overall are going to be
more common than thoracic
aortic aneurysms.
06:56
Having said that, we're going to
talk about thoracic aortic aneurysms
because they're important
to recognize them,
we understand some of the etiology
as we discussed previously.
07:04
Hypertension is going to be the most
common cause in most developed countries
for thoracic aortic aneurysms
and this can be ascending aorta.
07:12
This could be over the arch, this could
be the intrathoracic descending aorta.
07:18
All of those.
07:18
So hypertension is
going to be most common,
and that's again because we
are compromising the lumina,
the vessel lumen of those
vessels of the vasa vasorum.
07:29
Marfan Syndrome will
be another cause
of thoracic aortic aneurysms
usually in families.
07:35
But we can have spontaneous
mutations of the fibrillin gene,
Loeys-Dietz syndrome again because
of defective or abnormal TGF-beta,
and TGF-beta
receptor signalling.
07:45
Syphilis is a relatively
uncommon cause
at least in developed countries
for thoracic aortic aneurysms.
07:52
But because the syphilitic
organisms the Treponema pallidum.
07:56
like to infect the vessels of the
vasa vasorum of the arch of the aorta.
08:02
Iit is a cause of
thoracic aortic aneurysms.
08:05
We tend not to see
syphilitic aortitis
and syphilitic aneurisms
anywhere below the diaphragm.
08:12
So how can this present in
terms of symptomatology.
08:16
So many thoracic aortic aneurysms
may be totally asymptomatic.
08:21
Okay, that is just a given.
08:24
They may have respiratory
difficulty or stridor or dyspnea.
08:28
Because of compression of the
trachea or some of the bronchi.
08:34
Just as the thoracic
aneurysm expands,
they may also compress
pulmonary vessels.
08:40
So you may have a degree
of dyspnea associated
with extrinsic compression
by enlarging aneurysm.
08:47
They may have difficulty
swallowing dysphagia.
08:49
This has to do with the
innervation of the esophagus
and also the compression external
compression of the esophagus.
08:57
So they may have dysphagia.
08:59
A persistent cough
again is because of
irritation of the
recurrent laryngeal nerve,
and they may even have hiccups because
of involvement of the phrenic nerves.
09:12
You can have thoracic
and back pain.
09:15
And this is related to
enlargement of thoracic aorta
and impingement on nerve fibers
that are coming out of the spine.
09:27
If you have dilation that's
near the aortic root,
then the aortic valve will
dilate, the annulus will dilate
and you may have
valvular insufficiency.
09:36
So aortic regurgitation
with now impressive
pressure and volume overload
in the left ventricle.
09:44
And this is just demonstrating a very
dilated aortic root in the thoracic aorta.
09:49
This could have potentially given
rise to aortic insufficiency.
09:57
The other complication
that is perhaps most feared
is that dilation of
the thoracic aorta
will give rise to a rupture.
10:08
And with roughly
the same statistics,
4-5 cm dilation: 1-2% per
year; greater than 5-6 cm:
that's going to be about 10% per year;
greater than 6 cm: 25% per year.
10:22
The same risk of rupture
occurs in the thoracic aorta.