How to Do/Read and Interpret the Arterial Duplex Exam - SD

Introduction

Hello, my name is Annemarie Kapinsky
and I'm from the Northeast Vascular Imaging Group
in Albany, New York.
I'm going to present today how to read
and interpret the arterial duplex ultrasound examination.
This presentation will
review the essential components
of an arterial duplex ultrasound examination.
We'll go through what areas of the vascular tree need
to be evaluated and diagnostic criteria
and some of the common pathology that we'll encounter.

Purpose of Arterial Testing

When we talk about arterial testing
and a patient presents to us,
the first question we really are asking ourselves is,
is arterial disease present?
And this is a very simple yes or no answer to this question.
And we can do this without using ultrasound technology.
We can use an ABI or indirect testing to find out whether
or not a patient has arterial disease.
Very simple, very straightforward.
Once we define the fact that there is disease present,
then we wanna go on to some sort of secondary modality
and locate the level of disease as well as try
to figure out the severity of disease.
And duplex ultrasound is the,
basically the best tool that we can do this,
with for our patients.
And obviously being non-invasive
and we can get a pretty complete evaluation
of what's going on when we start off here.

Power Doppler in Evaluation

I put this slide in here to discuss power doppler,
which periodically you may see a slide or two.
Certainly we can use it.
We can get extended field of views such as this
where we can see the common femoral artery
and then the bifurcation into the superficial
femoral and profunda.
Femoral and color and power is a great tool
and we can quickly go through the vascular system
and look at what's going on.
But when we suspect that there is pathology present
or plaque, we have to remove that
and evaluate that gray scale image in more detail.

Capabilities of Arterial Duplex Ultrasound

Now what can arterial duplex ultrasound do?
Well, we said we can identify the exact level of disease.
That's the best thing we can tell with that information
that can be used to direct the patient care.
Is it somebody who can undergo medical management
and just have, perhaps some lifestyle modification or,
or perhaps treatment with certain drugs?
Or is this a candidate that's best suited
for an intervention
or surgical bypass And ultrasound can provide enough
information to the clinician so
that they can make these decisions?
We certainly know that ultrasound can follow,
disease progression.
We do this all the time with carotids.
We do this as well in the lower extremity.
One of the best things about ultrasound is
that not only can we find the exact level
of the anatomy involved,
but we can differentiate stenosis from occlusion.
This is not something we can do with
physiologic testing.
We really can't define a almost occlusion from an occlusion
with the indirect test, but we can with ultrasound.
So we get anatomy and we get physiology.
So it's a great combination of both tools.

Patient Symptoms and Indications

When patients come to our departments,
they're gonna have a variety of symptoms.
It can be something relatively mild such as claudication
or pain when they exercise,
but then we can have more severe signs of ischemia such
as rest pain or ulcers or gangrene.
Then a lot of times we may be following patients
for non atherosclerotic problems such as a vascular trauma
or our iatrogenic injury.
And of course we know that we follow
patients post-surgery or post intervention.

Pathologies Detected by Arterial Duplex

The things that we can detect when we do arterial duplex,
certainly it's atherosclerosis.
That's the primary pathology
that we see hardening of the arteries.
Another very common occurrence that we'll evaluate arteri,
lower extremity arteries
and even upper extremity arteries is for aneurysmal disease
or pseudo aneurysms.
We can also find dissections, intimal tears,
arterial venous malformations or arterial venous fistula.
Fibromuscular dysplasia.
FMD is less common in the periphery,
although you can see it in larger vessels
such as the iliacs.
And a little less common than
that even is evaluating patients.
For thromboemboli, this is usually an acute event.
We don't often see them in the ultrasound departments,
but they rather go straight on to an interventional suite.

Areas Evaluated in Lower Extremity Arterial Ultrasound

Okay, what areas do we look at when we do the lower
extremity arterial ultrasound?
We pretty much start right about here,
right at the groin crease, which is just
below the inguinal ligament
and this is the common femoral artery.
Now, depending upon what we see in the common femoral
artery, we may wanna extend the
evaluation further north to include the iliac vessels
as well as the aorta.
Hopefully, if everything looks good here at the common
femoral artery and our waveforms are acceptable
and we can continue on down and just go on down distally
and incorporate really the bulk of the lower extremity exam
just down from the common femoral.
We're going to include the profunda femoral
or deep femoral artery.
We don't really get to follow it for too long,
but we'll examine it.
And as it's a major supply
to several large muscle segments in the limb, we'll scan
through the entire length of the superficial femoral artery.
Somewhere about the adductor canal though will,
it will come deep and come up behind the legs.
We'll have to change our approach
and then we'll scan the tibial level vessels.

Tibial Level Vessels

In terms of the tibial level vessels.
If we look from an anterior approach as this, limb here
to the left of the screen shows,
we can see the anterior tib coming out
through the interosseous membrane,
coursing along the lateral edge of the tibia,
continuing down on the limb, down, down,
down crossing the ankle joint.
And at this point it's called the dorsal pedis artery.
So we'll try to evaluate this entire length of this segment.
On the flip side, if we look behind the limb,
this is a posterior view of the calf.
We see the popliteal artery here.
As we said earlier, it's going
to be basically the continuation of the vessels
after it's gone through the adductor canal.
We could see here, here's our anterior tib coming off
this segment from here to here
is termed the tibioperoneal trunk.
And its length is rather,
rather variable in individuals.
Sometimes it can be very, very short.
Sometimes it can be three or four centimeters in length.
The posterior tibial artery comes out
and courses medially kind of near the tibia,
again coming behind the ankle.
The peroneal artery, which also used
to be called the fibular artery, is right on top
of the fibula and deep in the calf
and sometimes difficult to evaluate in some patients.

Upper Extremity Evaluation

In terms of looking at the upper extremity, large vessel,
upper extremity disease is pretty rare.
Probably less than five to 10%
of our patients will be evaluated for disease, say,
involving the subclavian, axillary or brachial arteries.
Up and through here we see a lot more evaluation
of the upper extremities nowadays prior to, use
of the radial artery for CABG
or prior to the creation of an AV fistula,
which we'll talk about that in a little bit.

Protocol for Arterial Duplex Examination

The protocol is not too complicated.
When we're looking for plaque,
we're gonna use our workhorse transducer somewhere
mid-range, five to seven megahertz.
A curved array is helpful, particularly behind the knee
deepen, the lower thigh or around the clavicle.
When we're evaluating those vessels,
we're gonna position the patient such that they
externally rotate their leg at the hip
and slightly flex their knee.
Now this may be difficult for some patients
and we may need to put some support pillow
or blanket under the knee,
particularly if they have any type
of arthritis in their hip joint.
We're gonna use a combination of color to guide B-mode imaging to identify plaques
and spectral doppler to get our velocity criteria.
And we'll go through all the segments that I just mentioned.
We're gonna sample again, common femoral profunda,
proximal mid and distal SFA.
Most folks choose to record an above knee
and below knee portions of the popliteal as well as the,
the three main tibial vessels
and continuing down onto the foot with the dorsal pedis.
As I said, sometimes we are required
to look at the aorta in the iliac vessels in some labs.
If the common femoral is okay, we don't have
to include those more proximal segments.
We usually begin the exam somewhere around this level
and some folks refer to this as the Mickey Mouse sign.
Where Mickey's face here is the common femoral vein.
One ear is the common femoral artery.
The other ear is the great saphenous vein,
but this is about just below the inguinal ligament.
This is the common femoral artery
and this is where we wanna start our examination.

Normal Arterial Findings

Normally arteries should be nice and smooth and thin walled.
We'll be able to appreciate the intimal medial
boundary in many vessels.
Obviously as we get plaque,
we're gonna see the same changes we would expect
to in any artery.
We're gonna see that that plaque developed.
We're gonna see calcification, wall irregularities
and wall thickening occur in these patients.
Here is a nice, normal, very healthy, artery.
We can see the walls are thin
and smooth here, no evidence of plaque companion vein here
below it with a nice valve leaflets
color is gonna be our guide.
It's gonna be our tool
and we're gonna use that to rapidly
identify the course of a vessel.
In this particular vessel,
we see nice normal color filling out to the walls.
Continuing on through the superficial femoral artery here
from the common femoral over here.
If we look down this way, the profunda femoral artery
or deep femoral artery is taking off
and we see good color filling the air at the origin,
although we're at a little bit different angle,
so we're getting some color dropout
and we'd probably want
to angle back in a different direction
to get better color filling in the profunda.
But this is really about the only segment
of the profunda we typically evaluate.
Here's another image of a small tibial vessel
where this is what we wanna see.
We wanna see this beautiful color filling right up
to the edges of the vessel.
We don't want it to spill out into the tissue,
but if we suspect anything, again we have
to turn the color off and look at the gray scale.

Intimal Medial Thickness

Now, I mentioned briefly the intimal medial thickness
and I only mention it in this application
as some folks have chosen
to measure it at the common femoral artery,
you basically place a caliper at the interface
between the vessel wall and the blood
and at the next bright interface,
which is really delineating the media
and adventitial boundary.
And some folks feel that even in the absence of plaque,
classic plaque as we would call it when we see
that this intimal medial thickness increase in patients,
that that could be a marker for systemic atherosclerosis
and certainly the prevalence of coronary artery disease
increases as the IMT increases.

Examples of Disease in Arterial Duplex

Now let's get back to the main, goal
of arterial testing here in the lower extremity.
We see a relatively nice normal common femoral artery over
at this end of the image and scanning down.
What do we see? Well, we see two things.
We see the vessel is pretty significantly dilated,
at least about twice the, the luminal size as it is up here.
And we could see all this debris.
Now this could be some plaque,
this could be laminated thrombus.
It really doesn't matter
because it's there and it shouldn't be.
And we need these type of images to define what's going on.
And that information then can be used
to determine what's best for those patients.
In this particular patient,
we can see continuing on down into the common femoral
artery, we don't really see any kind
of narrowing in the flow channel.
Good filling out.
So most of this disease is really not encompassing,
any
of the superficial femoral artery in this example,
but it is, filling in along the back wall here
and partially obstructing the profunda femoral artery.
In this particular patient.
This is an examination of our classic,
or I should say this is a ultrasound image of our classic
plaque that we would see during an arterial examination.
Here's the plaque here we can see some calcification
and some acoustic shadow.
Now if we want a better evaluation
of what's going on along the back wall,
we're gonna need to change our approach.
We're gonna need to scan in from this direction
or perhaps from this direction in this particular patient.
There's two problems going on in
that there's not only plaque in the artery,
but there's some chronic thrombus here in the vein as well.
Calcification, again,
will produce the acoustic shadow behind it.
Sometimes you see very fibrotic plaque,
which will look bright white,
but typically calcification will give you
the shadow behind it.
Here's a, a radial artery,
which is showing some intermittent
brightness in the vessel wall.
Maybe a little bit of acoustic shadow here and there,
but if we have any doubt,
what we'd wanna do is take this vessel,
go into a transverse scan
and then slightly compressed with the transducer such
that we can see whether or not it's compliant.
Maybe there's some intermittent calcification,
maybe there's just some intermittent wall thickening.
But if we can compress that artery,
with ultrasound probe pressure,
then it's still a compliant vessel
and we're okay

Spectral Doppler Principles

in terms of spectral doppler, we need
to follow all the rules we do for doppler anywhere else in
that we should maintain a 60 degree angle or less.
Our sample gate should be placed in the
center of the vessel.
So we collect center stream flow in terms
of our doppler data
and the doppler beam should be aligned to be parallel
to the vessel walls, not parallel
to the flow jet parallel to the walls.
There was a good paper published years ago by Bob S
who said that really the significance
between the two was there was not much
of a clinical significance.
We can always see the vessel wall
and that's probably a better thing to shoot
for particularly since color is average data
and there's a lot of helical flow
and different flow patterns.
So the color really isn't truly representing
all the various components of the flow profile.
So let's just align to the vessel wall
and that'll be, that'll be our gold standard.
Now if we measure volume flow,
which I'll talk about in a little later,
we wanna open our sample gate pretty wide.
The measurements that most folks record really are peak
systolic velocity and the velocity ratio.
Some folks note the end diastolic velocity, it's not
as important,
but some folks note it in the presence of disease
'cause we'll see that end diastolic velocity change.
The velocity ratio is simply calculated
as the peak systolic velocity within the stenosis divided
by the peak systolic velocity just proximal to the stenosis.
And of course, as with any disease,
we're gonna document post stenotic turbulence.
There is a wide range of blood flow
and velocity in patients in the periphery.
It's not like the brain where flow is autoregulated
and there are varying levels
of resistance depending upon the patient, their activity,
if they've had coffee, if they're taking certain medicines,
the vessel sizes differ.
Muscle and tissue mass differ and all those come together
and give us a pretty broad range.
So an absolute velocity is not often used to define normal,
but rather velocity ratios, certainly
as we see stenosis, again will get spectral broadening
and we may see, the post stenotic turbulence
with a true stenosis.
This sketch is just thrown in here to, to remind us that
as we go down the arterial tree, we change
that very pulsatile flow into more continuous lower velocity
flow so we can get good exchange at the capillaries.
So velocities tend to drift down
as we go out the vascular tree.
Now in general, in peripheral arteries velocity is less than
150 centimeters per second,
although again you'll see very
broad range in velocities.
A better value to pay attention
to is the velocity ratio.
Obviously it should be pretty much the same
or certainly less than 2.
As we get an increase in velocity that's doubled,
we're really consistent with a 50% stenosis.
As our velocity ratio increases to four to one,
we're greater than a 75% stenosis.
And this is a pretty classic,
grading pattern
that many people use.

Waveform Interpretation in Duplex Ultrasound

Now the waveforms we see on duplex ultrasound tell us a lot.
Normally when the systolic pulse is delivered
to a vessel, that pressure makes the vessel expand slightly.
We can see that on ultrasound. In systole.
The vessel expands a little bit
and as the vessel expands, that expanded segment
of area actually holds a volume of blood flow.
And during diastole, when pressures drop, the elastic recoil
and the compliance of the vessel results in that vessel
contracting back or recoiling back.
And the vessel size decreases
and that volume of blood
that was held out here gets propelled down
the vascular tree.
So when we see a blood
flow sample from a peripheral artery, we can see here that
we have nice sharp upstroke consistently
A narrow peak, a rapid deceleration.
This below the baseline is the reflected wave.
That's the blood going down the vascular tree hitting the high
resistance arterioles and getting kicked back
or reflected back.
And this antegrade flow that we usually see in many patients
is the result of that little bit
of blood held out against the walls of the vessel.
And when the vessel recoils in diastole, it sends
that blood on down south.
Now we can see this nice normal
phasic pattern in this example as well.
Sharp up stroke, narrow peak reflected wave, a little bit of
antegrade flow at end diastole.
However, even though this is nice and normal
and our velocities here are within a normal range,
they're like 71.
If we look at the image, the image isn't normal.
So we can't call this normal vessel.
We can see this bright white calcification here,
a little bit of shadowing.
So while the velocities are within normal limits,
it's not a normal study
and there's some evidence
of very mild disease going on in the superficial femoral
artery scanning on down.
This happens to be the same patient at the popliteal artery.
Not much going on.
Maybe a little bit of plaque
or a little bit of thickening here
and certainly normal velocities.
So this is again, normal velocities,
but some subtle changes on the image.
So we can't call it a normal study.

Abnormal Waveform Patterns

Now what if we don't see that phasic pattern?
What if we see a pattern that basically has one component,
it doesn't cross the zero baseline,
we just move forward in systole
and there's no diastolic flow?
Well, that's most often associated with observing
flow signal proximal to a high grade stenosis or occlusion.
Here we see flow, no flow flow, no flow.
And in this example we're basically right at a stenosis,
but if we were just in front of it,
we'd see the same example as well.
Now what about a low resistance monophasic pattern
where again, we have no reverse flow component,
just forward flow,
but forward flow throughout the cardiac cycle?
Well, that indicates that there's vasodilatation going on.
Something has changed the resistance of that tissue bed
and we usually will see this if we're distal
to a high grade stenosis or occlusion.
Let's look at this example.
If we ignore the velocities here
and just look at the waveform, that waveform is not normal
for a peripheral artery.
There's a lot of diastolic flow.
We should never see that unless the patients just run up the
stairs to get to our department
or we've just run them on the treadmill.
We'll see some diastolic flow.
But the other thing to look at in this example is
that upstroke that slope.
And if we look here, the slope is kind of prolonged
as compared to our normal example
where the slope goes up pretty fast, pretty normal.

Role of Color and Power Doppler

Now color really is a complimentary tool,
but it certainly is an essential tool
to get this done and do it quickly.
We can put color on, we can find the vessels,
follow the vessels along the color will tell us if
something's going on, if there's turbulent flow
and certainly color
and power doppler are gonna be an adjunct that we can use
to identify an occlusion versus near occlusion.
And this example here of this bypass graft,
we can see nice healthy color flow over here, nice
and red, looking good.
But as we go down the vessel here, well what's going on,
what's going on is that we're seeing a lot of aliasing.
Something is impacting that signal.
So what is that something?
Well, that we take the color off and we look
and we see that there's this major stenosis here.
And whether this was a missed valve or hyperplasia
or new plaque, it doesn't matter.
We've identified it both on color and on gray scale
and it has to be fixed.

Reporting Arterial Duplex Results

When we're all done with an arterial duplex,
we can create a sketch like this if you want
plopping in all the numbers.
It's gonna be a matter of
what your preference is for your departments.

Upper Extremity Duplex Applications

In terms of upper extremity duplex.
As I said, a lot of it is gonna be small vessel disease,
vasospastic disease, which we won't do duplex for,
but some of the applications
of upper extremity duplex are listed here.
Certainly a large one is the evaluation
of the radial artery prior to harvest for CABG.
We can also evaluate the radial brachial arteries prior
to the creation of a dialysis fistula.
Will also be asked to evaluate those dialysis fistulas,
which is a, a topic for another discussion.
And although less commonly, we may even be asked
to look at the internal mammary artery
or IMA in folks prior to having a CABG.

Radial and Ulnar Artery Evaluation

Now the radial vessels are smaller and more superficial.
So we're gonna wanna maximize our near field resolution
and use a higher frequency transducer
for those patients perhaps getting a radial artery harvest.
We're gonna look along the entire course of both the radial
and ulnar arteries.
We're gonna look for pathology,
we're gonna measure the velocities
and vessel diameter in those patients.
And if you want, you can measure volume flow,
although it's not too common.
This slide here is showing
that we can measure diameter well in either
sagittal or transverse.
Transverse is the textbook way to do it.
And in this example, our variation one measure to the other.
This is 2.8 millimeters.
This is 2.6 millimeters, not very, different,
certainly not gonna be clinically significant.
However, if you're looking at things transversely, you know
that you're not oblique to the vessel
and perhaps have slid off a little bit
and your measurements will thus be off in a sagittal
approach if you're not careful.

Volume Flow Measurements

Now I mentioned volume flow earlier.
Some folks do volume flow measurements.
And here we see an example of a radial artery
and we've measured the volume flow.
And what we do is we dial in the diameter of the vessel,
the machine calculates the area, then we select
cardiac cycles for the system
to calculate the average velocity.
We start here, we've ended here,
we've included four cardiac cycles.
We wanna do as many as we can to get a good average.
And in this, with this equipment, it's fit this kind
of aqualine here, through the curve
and it's calculated the mean velocity.
So mean velocity times the area gives us our volume flow
in radial arteries.
Most of the time the diameters are pretty small, two
and a half to three millimeters.
Females are slightly smaller than males.
Velocities have some variability
but are somewhere around 40 to 50.
If we're looking at a patient
that's undergoing perhaps a evaluation prior to
a dialysis access being created,
we'll usually evaluate the brachial radial
and ulnar arteries.
We're gonna do several diameters, of each of these vessels.
And in some way we're going to evaluate the palmar arch
for its patency and continuity,
whether this be on ultrasound
or physiologic testing, most folks do some sort
of adjunctive procedure
to indirectly evaluate the palmar arch.

Internal Mammary Artery Evaluation

As I said, IMAs not very common.
One little bit of information.
If you can scan a vertebral, you can scan the IMA.
In this slide here we see the ribs
and we can see the images right here
and we can see right below it this flow channel.
And that is the internal mammary artery.
Just like we would expect to see the transverse processes
of the cervical vertebrae
and the vertebral artery beneath them,
this has the same appearance as that.
The IMA is a high resistance bed, so we expect
to have a high resistance signal.
The vessels are small, only two to three millimeters.

Aneurysmal Disease

Not everything we look at is plaque.
And we do evaluate, the arteries
and find aneurysmal disease.
The classic definition of an aneurysm is a 50% increase
in the vessel size compared
to the more proximal adjacent segment.
So sometimes a smaller
overall measurement may be more significant,
particularly in a female that has smaller arteries to begin
with, this common femoral artery is about 2.4 centimeters.
So it's pretty big considering
that most common femoral arteries are
around a centimeter or less.
So that's quite a significant increase
and that is reflective of, aneurysmal disease.
I put this signal in here to show
that we really don't wanna record a doppler from within the
dilated segment of an aneurysm
because obviously the doppler is disturbed
because of this large sac area, we've disturbed
that laminar flow profile.
Most of the aneurysms we see in peripheral arteries are
popliteal artery aneurysms.
They really account for about 70% of all aneurysmal disease.
Most aneurysms are the result of atherosclerosis,
although we can get aneurysms which form as a result
of trauma or infection or vessel entrapment.
It's predominantly a male, disease, 30 to one odds,
for male presentation as compared
to female presentation.
And we know that aneurysmal disease is often
bilateral and multilevel.
So we'll look at if we find a popliteal artery,
we'll look at the other popliteal artery
and maybe the common femorals and the iliacs and the aorta.

Symptoms of Peripheral Aneurysms

The symptoms that patients present when they have peripheral
aneurysms are gonna be quite varied.
Many may not have any symptoms at all.
Some may have just some vague symptoms of pain.
Some may have symptoms of venous compression where
that aneurysm is pressing down on the vein,
limiting the venous return
and causing some edema and swelling.
And sometimes the aneurysm actually will cause
nerve compression
and, some pain as the result
of the impingement on the nerve.
The important thing when we talk about aneurysm is
to make sure we document whether it's open
or whether it's occluded.
In this example, we see an old slide
of a pretty large popliteal artery aneurysm.
It's over four centimeters in diameter,
but there is a residual lumen
and there is flow coursing over
and through all this laminated thrombus.
So this presents a significant, risk to the patient
for venous thrombi
or for thromboemboli to the digital vessels,
mostly down,
resulting in something like a blue toe syndrome.

Iatrogenic and Traumatic Injuries

Briefly, I'll just mention some of the iatrogenic injuries
that we can encounter.
Again, we see plaque, we see aneurysms,
and we also see some other types of injuries to arteries.

Pseudoaneurysms

Pseudo aneurysms are a common occurrence.
They happen after vessel catheterization.
There are more common following an interventional procedure
versus a diagnostic procedure
because we are using larger bore catheters.
And basically it's a puncture site that fails to heal.
We make a hole in the artery, as shown over here.
We should hold pressure on it, compress it, allow platelets
to aggregate and a stable clot to form.
But if we just don't hold long enough, what's gonna happen?
Well, it's not gonna hold and it's gonna break.
And we're gonna see blood extravasated outside the artery
and creating this false aneurysm
or pseudo aneurysm encompassed by some
of the connective tissue around the outside of the vessel.
An ultrasound, we'll see a classic yin yang kind
of appearance to the color.
The swirling appearance
as the blood comes in hits the dead end
and swirls back out here is a longitudinal, scan
of perhaps the common femoral artery.
Here's the tear
or the defect in the vessel wall resulting in the neck
or the track into this large pseudo aneurysm sac.
Now, years ago we could use ultrasound
to help treat these patients and compress those sacs
and get them the thrombus,
but that was really a challenge both
for the technologist and the patient.
So now we primarily use thrombin injection
where under ultrasound guidance, a needle is placed,
thrombin is injected.
We will look and watch the thrombus occur within our eyes.
When we're all done, we see nothing.
We see no color flow and a thrombosed pseudo aneurysm.

Arteriovenous Fistulas

Another complication that can be observed following trauma
or catheterization are arterial venous fistulas.
Some AV fistulas may also be congenital.
And it's basically an abnormal connection between an artery
and a companion vein.
And in order to determine whether
or not we're really dealing with a fistula,
you can always occur with, decide what's going on
by examining the contralateral limb
and, comparing those signals bilaterally.
Here we see a color flow image.
This big bruit going on a bit of the vein underneath it.
We put the doppler in there
and sure enough, there's this high
velocity low resistance doppler signal that's,
in this fistula from probably the superficial femoral
artery to the either the femoral vein
or common femoral vein Early on, a fistula is not
that big of a deal while it's taking blood
and putting it into the venous circuit.
It usually doesn't result in any other problems.
However, if left untreated, some fistulas can get larger
resulting in an increased pressure in the venous system,
which will blow out valves
and it can actually result in a distal arterial
steal in some patients.
So they need to be taken care of.
As I said, if we look at signals right to left,
we'll know if we're dealing with a fistula.
Here is a Doppler wave form,
but the spectral doppler wave form on ultrasound would look
similar in the right limb here.
This is a normal high resistance multiphasic
pattern in the left limb.
Here this is indicative of low resistance, lots
of diastolic flow,
and in this case that diastolic flow is going out
through a fistula into the deep venous system of the leg.

Emboli, Thrombi, and Dissections

As I said, emboli
and thrombi, we don't often see
emboli can arise from the heart
or maybe from ulcerative plaque more proximally to the area
that we're evaluating.
However, because it's an acute event,
we usually get pretty severe pain.
Acute arterial ischemia results in the five Ps, pain,
pallor, pulselessness, paresthesia and paralysis.
There's some folks talk of a sixth p poikilothermia,
which means coolness.
And this is so sudden and so acute.
We usually don't get them over for an ultrasound,
but we bring them in to the interventional suite
for an embolectomy.
If we see them on ultrasound though the adjacent vessel here
is free of disease, nice normal looking artery
and just this big, thromboemboli sitting here
with a little bit of color flow around it dissections.
Again, briefly dissections can be observed
in peripheral arteries.
We wanna look at it from multiple views.
We wanna make sure we're not seeing an artifact.
We'll see color in doppler in both the true
and false lumen of a dissection.
A harder thing to evaluate are these small defects such
as an intimal tear or flap.
Sometimes people may dislocate a knee or an elbow
and were asked to evaluate the adjacent vessels,
making sure there was not a traumatic injury to the artery.
We need to really zoom up on the vessel wall, pay attention
to the gray scale 'cause that's how we're going
to see these very subtle defects.
And then sometimes we get arterial problems
that really have no name.
This was a patient who just had this slow oozy kind
of bleed out the brachial artery.
It wasn't a pseudo aneurysm, it wasn't encompassed anyway,
it was just extravascular blood flow
that we knew shouldn't be there,
but it really wasn't, a named pathology such
as a pseudo aneurysm.

Conclusion

So to conclude, duplex ultrasound can provide the exact
information we need on the location and severity disease.
We certainly can identify plaque,
but in addition, we can identify traumatic
or iatrogenic injuries as well.
And the wonderful thing about ultrasound is we not only get
this anatomy, but we get excellent physiologic data as well.
So we get anatomy and physiology for a complete picture
of what's going on in these peripheral arteries.
Thank you very much.