Ultrasound Evaluation of the Aorta and Peripheral Arteries - SD

Introduction

Hi, my name is John Palita.
I am the chief division of Ultrasound CT and MRI at North Shore University Hospital in Manhasset,
New York, that's Long Island
and my presentation is entitled Ultrasound Evaluation
of the Aorta and Peripheral Arteries.

In this presentation we're gonna talk about the sonographic
evaluation of the abdominal aorta, talk about the evaluation
of aortic endograft.
Then I'm gonna move into the evaluation
of the peripheral arteries and talk about pseudo aneurysms
and arterial venous fistulas.

In this presentation, we're going to discuss the evaluation
of abdominal aortic aneurysm complications
of endograft repair.
We're going review the diagnostic criteria
for arterial stenosis and discuss the diagnosis
and therapy of pseudo aneurysm and arterial venous fistula.

Ultrasound Evaluation of the Abdominal Aorta

We make the diagnosis
of abdominal aortic aneurysm when the aortic diameter is
greater than three centimeters meters.

When the size
of the aneurysm is greater than six centimeters,
then we become concerned
because they have a 50% one year survival rate
with a 43% risk of rupture.

In general, we say the aneurysm will increase in size about
0.2 to 0.4 0.4 centimeters per year.

Indications

Indications for the evaluation of the abdominal aorta
include patients with palpable pulsatile, abdominal mass,
unexplained lower back pain or abdominal pain,
and patients with known extremity aneurysmal disease.

Sonographic Evaluation Protocol

For our sonographic evaluation, we're going to
evaluate the extent of the aneurysm in both longitudinal
and transverse planes.
We're going to determine the amount
of intraluminal thrombus.
We're going to assess the residual lumen, look for evidence
of per aortic hematoma,
and also assess for involvement of the renal
and iliac arteries.

Usually for this study, we like
to have patients perform a 12 hour fast prior
to the examination and this reduces the amount of scatter
and attenuation from bowel gas.
We don't give any premedication normally
and we typically will scan the patient in
the supine position.

Normal Abdominal Aorta

The normal abdominal aorta typically demonstrates smooth
margins and tapers distally to the iliac bifurcation.
The normal diameter usually about two centimeters or less,
and it's important to recognize
that the abdominal aorta supplies both low
and high resistance.
Arterial beds here are two samples taken from the abdominal
aorta at the proximal and distal levels.

The sample obtained from the proximal abdominal aorta
demonstrates its forward flow component in cyst
and then is continuous forward diastolic flow,
and this is related to the fact
that the proximal abdominal aorta supplies blood
to the liver, spleen,
and kidneys which demand continuous forward flow,
both in systole and diastole.

The distal abdominal aorta distributes blood flow
to the lower extremities, which typically have higher
resistance to to blood flow in the distal vessels,
so samples taken from the distal abdominal
to typically demonstrate high resistance
and the sample here taken just
above the iliac bifurcation shows early diastolic reversal
consistent with blood flow in the peripheral arteries.

As we'll discuss in a little bit the protocol
as taken from the a CR practice guideline
includes the acquisition of transverse images
typically in the proximal abdominal aorta.
Near the diaphragm will take an image in the mid abdominal
aorta near the origin of the renal arteries
and the distal aorta above the iliac bifurcation.
We also wanna get a transverse view at the
iliac bifurcation as well.
We will also be obtaining longitudinal images
and taking AP measurements of the abdominal aorta.
These measurements should be obtained from outer wall
to outer wall perpendicular to the long axis
of the abdominal aorta.

For focal aneurysms, we typically will measure the maximum
AP diameter to determine the size of the aneurysm
and of course we're going to determine the relationship
to the renal arteries.
It is also recommended that we obtain a transverse image
of the proximal common iliac arteries, longitudinal images
with AP measurements
of the proximal common iliac arteries right
after the bifurcation,
and I think it's also valuable to obtain some color
and spectral doppler information as well.
Depending on the question at hand.

Diagnosis of Abdominal Aortic Aneurysm

We typically will say that the patient
has an abdominal aortic aneurysm when the size
of the abdominal aortic is at least greater than
equal to three centimeters.
Of course, this relates to the size of the patient.
Patients with smaller body habitus may demonstrate
a focal aneurysm at less than three centimeters,
but in general, three centimeters is the cutoff that we use.

We say the study is negative
for an aneurysm when no aneurysm
or focal dilatation is identified
and the common iliac artery is also normal in caliber.

The study is in determinant when we have limited
or non visualization of the abdominal aorta
and common iliac arteries.

Examples of Abdominal Aortic Aneurysm

Here are a couple of transverse images from an
abdominal aortic aneurysm.
The gray scale image shows just a small amount
of thrombus along the periphery of the aneurysm wall.
When we turn the color on, we can appreciate
that there's a large amount of intraluminal,
an coic thrombus,
and that the residual lumen is smaller than we suspected
from the gray scale image.

Here are two sagittal images.
The gray scale image shows moderate amount
of intraluminal thrombus and the residual lumen color.
DOPA is very helpful to demonstrate flow in the residual
lumen and it also helps us
to direct the pulse sample volume.
When we obtain velocity samples.
You could see here we're taking the maximum AP di dimension
to estimate the size of the aortic aneurysm.

Here's an example of an aortic dissection.
The gray scale image is helpful,
but it allows us to see the luminal flap
or intimal flap very nicely.
In fact, sometimes it's easier to see that flap
with gray scale, but
because color can sometimes overwrite the flap
and it may be more difficult to visualize
with color doppler.
Here we can see that this flow in both the true
and the false lumen screening is an important part
of the assessment for abdominal aortic aneurysm.

Screening Recommendations

Recommendations for screening include men 65 years
or older women 65 years
or older with cardiovascular risk factors.
We also consider screening for patients
with a family history of aortic
and peripheral vascular aneurysmal disease
and screening populations can include a history of smoking,
hypertension, and first degree relatives with the disease.

Evaluation of Aortic Endograft

Let's move on and talk about the evaluation of patients
that have endovascular stent graft repair
for abdominal aortic aneurysm.
This is a recent alternative to surgical repair
of abdominal aortic aneurysms.
In these patients, a graft will be placed transluminal
through a small incision in the femoral artery
and then the catheter will be placed through the artery
and across the abdominal aortic aneurysm
and then the graft can be deployed in position
and expanded to exclude the aneurysm cavity.
Some stent grafts are totally supported
with stent structure while others are supported only
at the attachment sites.

If we look here, we could see a couple of examples
of stent grafts.
The one on the top demonstrates a bifurcated appearance.
The one on the bottom has a single body.
Many of these graphs can be modular
and consist of several components.

Complications of Endograft

There are several complications
to consider in the follow-up evaluation of endograft.
There can be bleeding following the procedure.
We look for evidence of endoleak either at
the anastomotic sites or from within the graft itself.
There may be evidence of aortic dissection.
Other complications can include infection distal ischemia.
There may be migration of the stent graft or fracture
or deformation of the graft as well as graft thrombosis
and ultrasound is very helpful in the
follow-up of stent grafts.

Looking for some of these applications,
CT is considered the primary modality for the evaluation
of endograft, but ultrasound can be very valuable
for screening and surveillance of stent grafts.
It is somewhat patient dependent in
that very large patients, very gassy patients may
not be particularly sono and difficult to evaluate,
but accurately has shown to be related to experience
and ultrasound has proven valuable in
defining complications of endograft.

Follow-up Protocol

One of the keys to the follow-up evaluation
of patients treated with endograft is
to measure the maximal aneurysm sac diameter.
After successful endograft repair,
the abdominal aorta should be stable in size
or actually get a little bit smaller.
The aneurysm should not increase in size if it has been
excluded successfully by the endograft.

For this study, we also assess for peri graft leakage
or endoleak, and we're also going to assess for flow
through the graft and look for evidence
of stenosis or occlusion.

As part of the scan protocol, we want
to identify the intra sac portion of the graft.
We wanna follow the graft from the proximal extent
all the way to the distal attachment site checking
for evidence of leak.
We'll examine the senal abdominal aorta above the graft
as well as the distal runoff vessels
that is the distal aorta or iliac arteries.
We wanna evaluate the full length of the under graft looking
for flow abnormalities
and we can assess those with color doppler
and by taking velocity measurements at multiple locations,
making sure that the graft is patent
and looking for evidence of stenosis,
we can use colo doppler to assess for any evidence
of intraluminal defects, look for evidence
of extrinsic compression or kinking of the graft,
and we can obtain maximal
and minimal graft diameters to make sure
that there is no significant change in the
caliber of the graft.

Examples of Stent Grafts

Here's an example of a bifurcated stent graft.
The gray scale image shows you
that the stent graft is echogenic
and we can demonstrate the walls of the graft very nicely.
We turn the color on to demonstrate flow within the graft
to make sure that the graft is widely patent, no evidence
of any stenosis.
We also use color to look for evidence of leak.
Color is also important to make sure
that we don't see any abnormal flow within the excluded
aneurysm cavity.

Here's a transverse view through the same bifurcated graft.
Again, notice on the image that we can see flow nicely
through the lumen of both limbs of the graft
and yet there's no evidence of abnormal flow
or signal in the excluded cavity.

In the sagittal view here on the right hand side,
we could place the sample volume in the limb of the graft
demonstrating normal velocity flow
and demonstrate normal flow characteristics assuring us
that the graft is patent
and there's no evidence of stenosis.

Assessment for Endoleak

During the study, we're going to assess for the presence
of flow within the residual aneurysm sac
after endovascular graft placement.
Again, any abnormal flow
outside the graft suggests the presence of an endo leak.
We also going to assess the size of the aneurysm.
Any in increase
or expansion of the aneurysm suggests the possibility
of a leak and any leak increases the risk
of aneurysm rupture.

So when we assess for the presence of endoleak, we want
to examine the entire abdominal aortic aneurysm sac
for any abnormal flow.
We want to document any extra graft flow that we see
and we want to identify the source of flow.
Many times we want to document that
by obtaining velocity waveforms for flow direction as well
as peak systolic velocity,
particularly in those type two leaks where we see them
arising from branch vessels such
as the inferior mesenteric artery or lumbar arteries.

Types of Endoleaks

Here are the different types of endo leaks
that we can see from the illustration.
Type one endo leaks occur at either attachment site,
which can be the proximal
or from the distal end of the graft.
Type two branch leaks occur from the branch vessels which
can bring retrograde flow back into the excluded aneurysm
sac, and we typically will see that from retrograde flow
through the inferior mesenteric artery
or through one of the lumbar arteries.

As we previously discussed,
Type three endoleak is is typically device related.
There's a breakdown or a separation of the graft
and we can have flow coming through the separation
or fracture of the graft.
Type four is related to a graft porosity
where there's leakage throughout the graft
and type five occurs when we just cannot define
the site of the leakage.

Examples of Endoleaks

Let me show you a couple of examples.
These samples were
provided to me by George Bjo at
Montefiore Medical Center
and George has a lot of experience with the evaluation
of aortic endograft.

Here's a nice example of a distal type one endoleak,
which we can see with CT correlation
on the CT scan on the left, we can see
that this contrast material within the graft as well
as leakage of contrast material into the lumen
of the aneurysm sac.
And this compares very nicely with the color Doppler image,
which show that there's active leakage
of blood from the distal anastomotic site into
the aneurysm sac.

Here's an example of a type two endo leak here.
The leakage is from the inferior mesenteric artery,
which is BL bringing blood flow
back into the aneurysm sac via collaterals.
And we can see here that blood is filling the sac
and we can identify the graft more posteriorly
and we can see that the graft is patent.

Ultrasound Diagnosis of the Peripheral Arteries

Let's move on to a discussion of the ultrasound diagnosis
of the peripheral arteries.
Now obviously a non-invasive diagnosis is a desirable
alternative to arteriography.
It should not only detect the presence of disease
but be able to distinguish severe from non-surgical lesions,
those that require therapy from those that do not.
We also wanna use this technique to evaluate the results
of therapy such as angioplasty, stents and bypass grafts.

Indirect Tests

There are two ways we can perform this study.
Typically, I like to start out with the indirect tests,
ankle brachial index, segmental pressure measurements,
pulse volume recordings because they're useful for screening
and can help demonstrate the level of disease.
After I perform the indirect test
and they suggest that there's evidence of a lesion,
then we can go on and either do ultrasound screening
of the entire lower extremity tree from the aorta down
to the calf or ankle level,
or we could do a more focused approach
where we could do a detailed study at the level
or segment of interest defined by those indirect tests

for screening the lower extremity.
With the Doppler ultrasound, again,
it can be a very time consuming extensive survey from the
aorta down to the ankle levels.
And of course here the goal is
to map the lower extremity arterial tree
and this can be very difficult
and time consuming, particularly in elderly patients,
diabetic patients where there's multis segmental
arterial occlusive disease.

And for most of our patients, this type
of screening examination has been supplanted
by other magnetic resonance or ct, an geography.

In our laboratory, we prefer
to do a focus duplex in color flow doppler examination,
again defined by an abnormal segment
identified by the indirect tests.
This approach us this approach allows us to
identify the location, length,
and degree of stenosis on the color Doppler image.
It allows us to perform a direct application
of arteriography for angioplasty and
or stent placement based on the color doppler
information that we obtain.
And we also use these techniques to follow patients
with known lesions for progression of disease
and to also evaluate therapy such as
stenting and grafts.

Protocol for Lower Extremity Evaluation

The protocol for the lower extremity evaluation Doppler
ultrasound, we want to identify the area of interest
with gray scale color and pulse Doppler examination.
Gray scale is used to define the presence
or absence of atherosclerotic plaque.
We use color doppler to sweep the area of interest
for narrowing and aliasing,
and this requires optimization
of the color doppler parameters.
This is a very important step
because it allows us to sweep the vessel very quickly,
looking for evidence of flow abnormality.

If we tweak the pulse repetition frequency
for flow in the normal area, then when we see focal areas
of increased VA vascularity, it'll show up
as a focal area of aliasing.
And once we identified these abnormal areas of flow,
then we can place the sample volume within this site
of flow disturbance To get out pulse dolar samples,
it's important to remember common sites
of atherosclerotic disease typically involving the
bifurcation points of the lower extremity arterial tree
and that would include the femoral bifurcation
popliteal trifurcation,
and it's also to remember
to evaluate the distal superficial femoral artery in the
region of the adductor canal, which is an important area
of disease in diabetic patients.

For these studies, we typically use a five megahertz linear
transducer, which works for most patients just as it does
for the venous examination.
If we have a very large patient
and then we may switch to the three megahertz transducer so
that we have adequate depth penetration in pediatric
patients or patients with small body habitus,
we can increase the frequency range to have
adequate depth penetration.

Again, we wanna optimize both the gray scale
and the color doppler parameters
to laminar flow in the vessels of interest.
We'll adjust the pulse repetition frequency
to detect hemodynamic disturbance
and then be able to perform pulseless samplings in the
regions of color aliasing.

Normal Peripheral Arterial Waveform

Now this is probably the most important slide
in this presentation of the peripheral arteries
because it defines normal flow
and of course it's important to be able
to recognize normal if we're going to be looking
for evidence of subtle changes of disease.

In our doppler samples.
The normal peripheral arterial waveform has
a phasic character.
We see our initial forward flow component in systole,
and this is related to ventricular contraction,
which propels the red blood cells down the lower extremity.
We typically see early diastolic reversal
and this is related to distal peripheral resistance.
And then later on we're going
to see a smaller forward flow component in systole
and we think this is related
to elastic recoil of the vessel wall.
So initially in systole, the vessel wall is expanded
and then it snaps back into place further propelling the red
blood cells down the lower extremity.

It's also important to note
that the normal peripheral arterial waveform should have a
narrow systolic window,
and that's the area under the curve here.
And this indicates to us that at the point
of the sample volume, all the red blood cells are moving at
approximately the same velocity at any given point in time.
And of course, we're going to notice the normal velocity
range and here in this sample taken from the deep femoral
artery, we see the peak systolic velocity is about 80
centimeters per second.

Obviously, it's important
to recognize normal peak systolic velocity ranges
for the vessels, and you can see here that as with most
arteries in the body, the peak systolic velocity ranges from
between 40 to 100 centimeters per second.
In the femoral arteries, the range is about 80
to a hundred centimeters per second,
and velocities will decrease
as we proceed down the lower extremity.
In the popliteal arteries, the velocity is 60
to 80 centimeters per second,
and when we get to the tibial arteries,
the velocities are in the 40 to 60
centimeter per second range.

When we evaluate samples
obtained from the lower extremities, there are three things
that we're going to evaluate.
We're gonna look at the waveform shape, is it phasic or not?
We're gonna look at the peak systolic velocity
and we're going to look at the spectral window.
These three characteristics are used to classify the degree
of disease in our examination.

Categories of Disease

Let's review the categories of disease.
We say a mild lesion is one to 19% diameter reduction,
and this occurs when there's mild narrowing
of the lumen of the vessel.
You could see here on the color Doppler display
that we have a lamina looking flow pattern within the lumen.
We place the sample volume in the region of narrowing
and make sure that we have adequate doppler samples
for re review.

In this patient, we can see
that the peak systolic velocity is about 140 centimeters per
second, so it's up
to a 29% increase in the peak systolic velocity compared
to the normal proximal segment,
and that's how we evaluate peak systolic velocities in the
lower extremity arteries.
We take a sample from the area of narrowing area
of focal disease in the vessel
and compare it to the normal proximal segment.
Typically about two centimeters proximal to the stenosis.
A mild lesion has up
to a 29% increase in the peak systolic
velocity compared to the normal segment.
We can appreciate in the sample that we maintain a normal
phasic waveform in patients

with a moderate lesion that is 20 to 49% diameter reduction
have a increase in spectral broadening that is fill in
of the spectral envelope.
We have up to a 99% increase in the peak systolic velocity
that is compared to the proximal normal segment.
And this example here in the common femoral artery,
we can see that there's narrowing of the lumen color.
Doppler shows us aliasing in the jet at the site
of the stenosis and pulse doppler sampling in the region
of the jet demonstrates a velocity
of about 180 centimeters per second,
which again is not going,
is not quite double the peak systolic velocity in the
normal proximal segment.
So we say it's less than a 50% stenosis.

Another important thing to remember that when we have a 20
to 49% stenosis,
we maintain the diastolic reversal in the waveform.
As we see here, this changes
when we have a significant stenosis

and we say a lesion is flow reducing
or significant when it's 50 to 99% diameter reduction.
At this point of luminal diameter stenosis,
we see a change in the flow pattern.
We lose our reverse flow component,
so we see flow only in one direction through the stenosis.
In this example, we have a high grade lesion in the right
external iliac artery.
We place the sample volume in the stenosis identified
with color doppler and we can see we're aliasing at over 300
centimeters per second.
Notice that the spectral window
or envelope is completely filled in marked
spectral broadening.
We have greater than a hundred percent increase in the peak
systolic velocity compared to the normal proximal segment.
We say the waveform has a monophasic appearance
that is flow only in one direction and this occurs
because at the site of a flow reducing lesion,
the red blood cells get sucked through the lesion
through the stenosis
because of the press pressure reduction on the
post stenotic side.

And as we continue to drag the sample volume
through the stenosis, we'll see
that there's a mark change in the waveform character due
to post stenotic turbulence with an occlusion.
We'll see a loss of flow, absence
of flow in the occluded uh segment.
As you'd imagine we'll see flow in the proximal segment,
which may have very damped waveform characteristics,
and this is related to the chronicity of the lesion
In an acute occlusion, we'll see very high resistance,
low velocity wave forms in the proximal segment
and we'll see very low resistance,
low velocity wave forms in the reconstituted segment
and patients with well-developed collateral flow,
we may maintain a low resistance pattern in the proximal
segment above the occlusion.

Here's an example of a sample taken from collateral flow in
a patient with severe arterial occlusive disease
and I want you to appreciate the low resistance flow pattern
that we see in these collateral vessels.
And these vessels are supplying ischemic vascular beds
and these vessels typically provide blood flow
to vasodilated arteries
and these vessels have very low resistance to flow,
so we see continuous flow diastolic flow.

The other thing to notice on the sample
is the rounded contour.
There's a delayed peak to systole, which we usually describe
as a TARDIS parvis flow pattern.
We could see it has a really rounded waveform appearance,
sort of a TP or or mountaintop configuration.
When we see these rounded waveform, we typically think of
proximal arterial occlusive disease.

I'd just like to show you this paper
that was published some years ago from ranking this group,
which illustrates the value of ratios for
defining peripheral arterial disease.
In this study, they showed
that there's marked variability in peak systolic velocity
measurement from the lower extremities,
and for that reason, peak velocity ratios work better
for divine defining levels of disease.
In this study, they also showed
that they can determine at least a 50% stenosis when the
peak velocity ratio from the stenosis
to the normal proximal segment is at least 2.4.
They define a level of disease
of greater than 80% stenosis when the ratio is greater than
four to one, and they classify a 90% stenosis when the ratio
is at least seven to one from the stenosis
to the normal proximal segment.

Color Flow Findings in Peripheral Arterial Disease

There are a number of important color flow findings
associated with significant peripheral arterial disease.
As I mentioned before, we look for an area
of focal color change
or aliasing at the side of the stenosis.
We may see persistence of color with a high grade lesion,
and this is related to a change from a pulsatile flow
pattern to a monophasic flow pattern,
which I'll show you in a sec.
And we can also look for evidence
of color bruery artifacts which are related
to perivascular tissue vibration.
We also see evidence of a column color mosaic pattern due
to swirling of blood flow in the post stenotic segment.

Here's an example of normal phasic flow.
In this example here, we could see
that there's alternating red and blue that is forward
and reverse flow in the femoral artery.
Again, as we sweep the vessel,
we can see there's a normal flow pattern,
and of course we can recognize normal phasic flow in the
underlying femoral vein.

Here's an example of disturbed flow
or persistent color
in a high grade lesion in the superficial femoral artery.
Notice how the color persists within the lesion,
and this serves as a beacon
or indicator of significant stenosis.

On our color Doppler exam with pulse doppler,
there are several findings we should be looking for
to classify peripheral arterial disease.
Again, we look for elevated peak systolic
velocities within the stenosis.
There's loss of diastolic reversal in the waveforms obtained
within the stenosis.
Many times we see evidence
of a brewery on the pulse stop or sample.
And again, as I mentioned earlier,
as we drag the sample volume into the post stenotic area,
we may demonstrate tardis parvis waveforms
distal to the high grade lesion.

Examples of Stenosis

Here's an example of a significant stenosis in the
superficial femoral artery.
We place the sample volume within the stenosis
and we see the peak systolic velocity is about 250
centimeters per second.
Now this is a monophasic waveform
that is blood flow is going in the forward flow direction
and systole and diastole.
You notice here that we see some information
below the baseline here,
and in fact, you should appreciate
that it actually occurs on both sides of the baseline.
It's a diamond shaped artifact
and this is related to perivascular tissue vibration.
In other words, this is a brewery that we see in the tissues
identified on the spectral tracing.

As we continue to move the sample volume into the
post-traumatic region, we see there's a marked loss in
velocity and a breakdown in the waveform shape so
that we have a disorganized flow pattern, low velocity
bidirectional with a rounded configuration.
Here again, we're seeing tardis parvis waveforms in the
posto area indicating the severity of disease.

Here's another example. This one taken from the
popliteal lottery, the high grade lesion scene in this
location, the peak systolic velocity
is about 200 centimeters per second.
Again, notice all the characteristics that we look for.
High velocity, spectral broadening,
continuous forward diastolic flow, loss
of diastolic reversal.
These are all the key findings that we look for
to classify a severe stenosis.

And as we continue
to move the sample volume into the post stenotic area,
again, we see a very disorganized flow pattern.
We lose velocity.
We have bidirectional flow and a rounded waveform.
The TARDIS parvis waveform again indicating
that this is a post stenotic waveform
and that there's significant proximal disease.

Let's take a look at this example.
Here's two waveforms taken from both
common femoral arteries.
It should be pretty clear to you
that the waveform from the right common femoral
artery is normal in appearance.
It is a phasic character, peak systolic velocity.
Within the normal range, we identify diastolic reversal,
whereas the waveform taken from the left common femoral
artery is low velocity,
has continuous forward diastolic flow
and has a rounded configuration, a TARDIS parvis appearance.
So this indicates to us
that there should be a proximal lesion, and
because we can garner this information from this waveform
shape, we will look approximately into the external iliac
artery and identify a tight stenosis at the level
of the external iliac artery.

The color Doppler image demonstrates aliasing at the site
of the stenosis, and when we place the sample volume at
that level, the peak systolic velocity is over 450
centimeters per second consistent
with a very severe stenosis.

Femoral Artery Injuries

Finally, let's just spend a couple
of minutes talking about femoral artery injuries.
Femoral artery injuries occur about 0.2
to 2% following diagnostic and therapeutic procedures.
The incidents of these injuries is increasing due to the use
of larger catheters, more complex procedures,
and the concomitant use of anticoagulation.
Early diagnosis is necessary
to avoid potential complications that can occur,
and these complications include large femoral hematomas,
pseudo aneurysm, arterial venous fistula,
arterial dissection, and arterial occlusion.

Pseudoaneurysms

Let's first discuss pseudo aneurysm.
Now, pseudo aneurysms are vascular masses
that are separate from the underlying artery
and are connected to the artery by a
communicating track or neck.
These result from a hole in the arterial wall
and blood flow escapes
through the hole into the surrounding tissues,
and the blood flow is confined
by surrounding soft tissues and hematoma.

These are usual related
to an arterial puncture from a diagnostic
or therapeutic procedure,
but may also be seen be seen related to other forms
of trauma or infection.
The most common predisposing factor to the formation
of pseudo aneurysm is insufficient manual compression
that is less than five minutes
of compression following the procedure.

We also see pseudo aneurysms occur with other types
of procedures such as simultaneous cannulation of
of the femoral artery and vein, the use
of intra balloon pumps,
continuous arterial venous hemofiltration, and
after angioplasty with or without stent placement.

Here's a clip of a pseudo aneurysm,
and on this real-time image you can see
that blood flow is escaping from the underlying artery
and is swirling in this mass that it connects
to the artery by this tract.
So we see swirling color flow within the cavity,
and if we freeze it here, we'll get
that typical yin yang appearance.
We can identify the communicating track
or neck between the artery and the pseudo aneurysm cavity.

If we place the sample volume within the neck,
we'll see a typical two andro flow pattern
and we can characterize that flow pattern
as we see high velocity jet entering the neck during systole
and a reversal flow back into the artery during diastole due
to a change in pressure.
And we can characterize that flow pattern very nicely
by placing the sample volume within the neck
of the pseudo aneurysm.

And here we can see blood flow going into the
pseudo aneurysm in systole,
and then there his reversal of flow back into the artery.
Throughout diastole to

Treatment of Pseudoaneurysms

and fur flow, there are a number of different treatments
that can be performed for pseudo aneurysm.
If the pseudo aneurysm is small,
typically less than one centimeter,
we can just watch the pseudo aneurysm.
We can be conservative and see if it's
spontaneously thrombosis.

When pseudo aneurysms are very large
or complex, it may go onto surgical repair.
Years ago, we used to perform ultrasound guided compression
repairs because it was a non-invasive treatment,
but today we prefer thrombin injection for the repair
of those pseudo aneurysms that were amenable
to ultrasound guided compression repair.

There are also other types of interventional techniques such
as balloon occlusion, which can be performed on unusual
types of pseudo aneurysms such as axillary
or brachial pseudo aneurysms.

Thrombin repair is a non-operative alternative
to compression repair.
With these procedures,
a needle is placed into the pseudo aneurysm cavity under
direct ultrasound guidance,
thrombin is then injected directly into the cavity while we
watch with ultrasound,
and in most cases, we see immediate thrombosis
of the pseudo aneurysm, and this has proven to be a fast
and effective treatment. Hold up
Right There. This
technique was originally described by Kang
and his group in the general of vascular surgery.

In his initial series, he described
thrombin injection in 20 of 21 consecutive pseudo aneurysms.
Typically, he would inject 0.5 to one milliliter of thrombin
into the pseudo aneurysm cavity
directly under ultrasound guidance.
In 15 of the 20 cases, there was immediate thrombosis
of the pseudo aneurysm occurring in less than 20 seconds,
five required a second injection,
and in his series, there were no
complications or recurrences.

Here's an an example from our series
that we published a few years ago,
and here we can appreciate.
Here's the femoral artery, here's the region
of the pseudo aneurysm neck,
and then we could see flow in the pseudo aneurysm cavity.
This patient was prepared for thrombin repair.
Typically, we assess the pseudo aneurysm.
We we get informed consent from the patient,
and then we will place the needle
into the pseudo aneurysm cavity.
Typically, we turn the color doppler off
as we place the needle so
that we can appreciate the location of the needle tip.
We wanna make sure it's in the center of the lumen
of the cavity away from the pseudo aneurysm neck.
The goal is to just inject the s, the pseudo aneurysm
with thrombin and avoid injection of the neck
or the underlying artery,
which can produce distal thrombosis or embolization.

Here in real time, we can appreciate the
injection, the swirling color.
You'll see that there'll be immediate thrombosis
of the cavity after the injection.

Here's another example here.
You could see that there's immediate thrombosis.

Arteriovenous Fistula

Finally, just let me discuss the diagnosis
of arterial venous fistula.
Here we see an example of a fistula
between the common femoral artery and vein.
We place the sample volume at the site of the fistula,
and we typically see high velocity
low resistance flow within the fistula.
And here's the arteriogram,
which shows contrast material within the artery
and the early draining vein.

One more example of arteriovenous fistula.
Again, I want you to appreciate
with the sample volume on the arterial side of the fistula,
we have high velocity, low resistance flow,
a change in the typical high resistance flow pattern
because now the blood flow is feeding a low resistance
circuit, so we go from a high resistance
to a low resistance pattern,
and if we move the sample volume into the venous side at the
site of the fistula, we see an arterialized flow
pattern in the vein.

Conclusion

In conclusion, ultrasound is extremely valuable in the
evaluation of the abdominal aorta about screening
and diagnosis of abdominal aortic aneurysm, as well
as defining complications of aortic endograft.
We use it routinely in the evaluation
of peripheral arterial disease
to characterize focal lesions, monitor disease progression,
and direct the appropriate interventions
and assess the response to those therapies.

And finally, in the diagnosis
and treatment of pseudo aneurysms
and arterial venous fistula.
Thank you.