Non-Imaging Tests - SD

Introduction

Hi, my name is George Bjo,
and I'm the director of the
Vascular Lab at Montefiore Medical Center in New York City.
And today, I'd like to discuss various techniques
as they relate to non-imaging tests for the evaluation
of patients with suspected peripheral
arterial occlusive disease.

Hi, I'd like to discuss the use of non-imaging tests
in the vascular laboratory.

Common Symptoms: Exertional Leg Pain and Claudication

Now, by far the most common symptom patients
with suspected peripheral arterial occlusive disease are
referred for is exertional leg pain.
This affects about 2% of the population, age 40 to 60 years
of age, and about 6%
of the population greater than 70 years.

The symptom that I'm referring to is genic claudication,
defined as muscular discomfort of the calf, thigh, hip,
and or buttock with ambulation.
This is often described as a cramping or an aching pain.
Sometimes as a, a pain in the muscles of the legs,
it's relieved by stopping the walking or the exercise,
and standing or sitting for about two to five minutes or so.

Genic, claudication is consistent
and very reproducible.

Patient History and Physical Examination

It's very important in this group of patients
to do a thorough history and physical
and ask, very relevant questions.
Allow the patient to talk to you,
ask the patient why they're there,
and then ask more focus, specific questions,
pointing them in the direction of the disease process
that you're ty, attempting to, exclude,
in preparation
for customizing the exam in that particular patient.

Important questions involve previous surgeries and
or interventions, and then, trying to elicit a history
for the appropriate risk factors.

In terms of claudication,
which again is the most common complaint,
you should ask the patient where in the extremity they're
experiencing pain, what the walking distance is in terms
of either feet or blocks
or miles, where they're experiencing the pain, how long
before they return to a normal state,
what the initial onset of symptoms is,
and if there's been any progression
of symptoms in the recent past.

Arterial Duplex Imaging

Now, it's not uncommon for many of these patients
to be referred for arterial duplex imaging.
And this is a good test.
It provides great direct anatomic
and physiologic information.
It's very good in terms of distinguishing
between stenosis,
and the occlusion of visualized vessels.
It allows you to, to determine the length
of the disease segment, as well as the patency
of the distal vessels.

However, there's one major drawback, in terms of,
duplex imaging, and that is
that it does not provide information
regarding the overall limb profusion.
And this is why we think that physiologic non-imaging
tests are so important.

Physiologic Testing Techniques

Now, one of the major components of the evaluation
of a patient, with suspected,
peripheral arterial occlusive disease is the pulse
examination, and will often, palpate,
pulses at the femoral level at the popal, as well
as in the foot over the dosis and posterior tibial arteries,
and then grade them accordingly.

However, this is, a very subjective examination,
and there really is a need for more objective evaluation.
And today I'll describe some of the,
physiologic testing techniques
that can be used in the vascular lab,
to evaluate the patient
with peripheral arterial occlusive disease.

Doppler Waveform Analysis

Now, let's start off with, a simple test.
It's the Doppler wave form analysis,
and this can be performed at either a single level
or at multiple levels, when you're doing a single level examination.
This generally occurs at the ankle,
using a handheld doppler, bidirectional
and, placing that doppler over the area
of the dorsal SPUs or over the posterior tibial artery.
And this is a quick method to determine the presence
and, relative severity of disease.

There are certain techniques that will be used,
and I'll describe those shortly.

When performing this examination at multiple levels,
levels, which is two or more,
you can listen over the pedal vessels, over the posterior,
over the, popliteal.
You can listen over the femoral in the thigh
and the common femoral artery, at the groin.
And this is a, a good technique
because it can help you to determine the presence
and severity of disease.
But, in addition, it can allow you to sort
of regionalize disease
by looking at changes in the wave forms
from one level to the next.

Make sure that you're testing the
patient in a resting state.
You'll need a warm room.
In many cases, the the vessels will be relatively
superficial, so the more superficial the vessel is,
the higher the frequency of the doppler, should be used.
Very important, you need to maintain at least a 45,
to 60 degree angle in order
to elicit the best wave form from the
area that you're examining.

And here's an example of, the angle that should be used.
So you can see here we're not at all perpendicular,
but in this case, listening over the distal anterior tibial
artery with a handheld doppler at about a 45
to 60 degree angle.

Now, the wave form,
when it's normal should be either try or biphasic.
We should be looking for a multiphasic waveform.
And here on the top is an example of a very normal, in fact,
quadri phasic waveform elicited from the distal,
dorsal PDUs in the foot.
We should be looking for a rapid systolic upstroke.
It should be very quick from the onset to its peak, as well
as some late systolic flow reversal.

Now, in more advanced stages of disease, we start
to lose the reverse flow component,
that second forward flow component.
So we, that loss of the phasic wave form.
And in this case, with a patient with a very,
proximal occlusion, we see a very severely blunted wave
form, no, reversal of flow,
a decrease in an amplitude, and also a dampened upstroke.
And this is a characteristic of severe
multi-level occlusive disease.

Pressure Measurements

Now, there are other tests that can be used as well,
and one of those is the measurement of a pressure.
We know that in normal individuals
who are in a supine position,
the ankle systolic pressure should be greater than the
pressure at the brachial artery.
Again, make sure that you're,
testing your patients in interesting state.

And here we see two examples, of a simple,
measurement of pressure at the ankle level
with the blood pressure cuff wrapped around the ankle.
Here we are eliciting a signal over the
distal anterior tibial artery.
Again, in this case, the posterior tibial artery.
The cuff is inflated, until the doppler signal,
is obliterated.
The cuff is then slowly deflated when the signal returns.
That's the pressure at the level
that the cuff has been inflated.

And again, we can acquire these
pressures listening over either the dorsal pettus
or the posterior tibial artery.
But more important, in terms
of the ankle pressure is the ratio
that can be calculated when you compare the ankle pressure,
to the pressure that's obtained at
the brachial artery level.
And, we call that the ankle brachial index.
A simple ratio, calculated by, divided
by dividing the ankle pressure by the higher
of the two brachial pressures.

And this is important. Always be sure
to calculate both brachial pressures
as there is some incidence of upper extremity,
arterial occlusive disease.
And so you need to make sure that you're acquiring both
of those brachial pressures
and using the higher
of the two brachial pressures in your calculation
of the ankle brachial index.

Again, you can use the dorsal PDUs
and the posterior tibial artery.
You can either report both pressures
or use the higher of the two ankle pressures when you're
reporting, your ankle brachial index.

And these are just some values that you should be,
familiar with.
The normal ankle brachial index should be greater than one.
Anything greater than about 1.3 or so.
You have to start to consider other issues,
which I'll talk about shortly.
Anything less than 0.9
or so, we start to, think about the presence of some disease.
The lower the ankle brachial index,
the more severe the disease process is.

Clau will often present with ankle brachial indices
of 0.8 or less.
Patients with multi-level occlusive disease,
or long segments of occlusion will often present
with ankle brachial indices of less than 0.5.
And patients who present
with ischemic rest pain often will present
with ankle brachial index of less than 0.3.

Another exception, in patients who are normal.
In fact, patients who have brachial systolic pressures
that are either below 100 millimeters of mercury
or above 200 millimeters
of mercury may not in fact exhibit the normal 1.0,
ratio.
And you have to be careful in these patients,
the ankle pressure may be in fact,
25% lower than the brachial pressure,
although this we don't see very often.

Now, you can take this simple, measurement
of pressure in the same principle
and apply it in multiple levels in the leg.
And, this provides very good information in terms
of segmental evaluation
because changes in pressure from one segment,
to the other if they're greater than 20 millimeters
of mercury, suggest the presence
of hemodynamically significant stenosis in
between those two levels.

And there are really two ways to do this.
We can use a three cuff method as you see on the top here,
with one cuff over the ankle,
one over the calf, and one at the thigh.
Or you can use a four cuff method,
which uses four 12 centimeter cuffs, one at the ankle,
one at the calf, one just above the knee,
and then a very high thigh cuff pressure.

And again, there are several ways to interpret the findings
of the pressures that can be obtained here.
You need to compare
to the contralateral limb at the same level,
or you can compare adjacent segments.
What you're looking for is, drops in pressure
of 20 millimeters of mercury or greater.
We call those gradients, especially in the presence
of an, an abnormal, ankle brachial index.

And this technique is very good, the segmental technique in
that it allows you to determine regions of disease,
and it's, a little bit better than the a BI,
which tells you that there is some disease present,
but not exactly where that disease is.

A couple of considerations with the,
the three cuff method where you're using a 17
centimeter thigh cuff.
If it's abnormal, often it cannot differentiate between
aortic iliac disease and femoral artery occlusive disease.

With the four cuff method,
you do have an advantage in that the upper thigh cuff,
when it's, decreased, the,
the thigh cuff pressure when it's decreased,
does clue you into the possibility of iliac disease.
But keep in mind that the normal thigh
to brachial index using a four cuff method will be 1.2,
because we do introduce some artifact
and that the cuff is a little more narrow,
than the cuff used with the three cuff method.

But again, it does help in terms of differentiating,
aerial iliac disease,
from femoral popliteal occlusive disease.
Of course, if you're using a three three cuff method
and you're not sure about what's going on in the iliacs,
you can always palpate a, a femoral pulse,
to exclude the presence of significant occlusive disease,
at the iliac level.

Now, there are several advantages
to these segmental pressure, evaluation.
Again, it gives you quantitative information
about limb perfusion.
Very easy to perform a very short, learning curve,
and it does give substantial, clinical validation,
that you could put together with your physical exam.

In terms of evaluating patients,
however, there is a limitation.
And probably the most, major limitation in terms of
the pressure measurement is the, presence of,
of medial calcification that, patients with diabetes
and end stage renal,
disease patients will often present with.

Now, in the presence of, medial calcification,
often, we will have art factually elevated,
blood pressures, and that renders the measurement
of the A BI as well as the measurement, of the,
pressures at the various segmental levels,
useless in these patients
because you really don't know that,
that those pressures, are valid.
And you have to be aware
that especially when your ankle brachial indexes in
excess of 1.2.

Digital Pressures

But there is a way, around that.
And one of the things you can do is you can measure a,
a digital pressure.
And the way we do that is by using a PPG sensor
at the tip of the toe.
We can then wrap a small toe cuff, inflate
that toe cuff until the signal, from the PPG disappears
slowly deflate the cuff until the PPG wave form resumes at
that level, we can measure the pressure.

And this is very good in patients, with, evidence
of medial wall calcification.
Again, those diabetics
and patients with end stage renal disease, the normal,
digital brachial,
index should be somewhere at about 0.6 or above.
At levels below 0.5, you can assume
that there is some significant,
peripheral arterial occlusive disease above that level.

Arterial Plethysmography and Pulse Volume Recording (PVR)

Another way to avoid the pitfall
of the pressure measurement is to do, use a another technique,
referred to as arterial
plethysmography, which really measures,
volume changes in a limb or, or an organ.
And the primary, plasmo graphic technique
that's available today is the pulse volume recording.
We refer to these tests as PVRs.
They measure volume changes in the limb during systole,
air is displaced within a cuff during the cardiac cycle.
The volume of displaced there is then displayed
as a wave form on a strip chart recorder.

And then we can analyze that waveform
by both looking at the height of the wave form,
which we refer to as the amplitude, as well as the shape
of the waveform by looking at the waveform morphology.

And this is just a series of waveform here
with varying degrees of disease.
To the far left, we see a very normal waveform
with a very sharp up stroke, a reflected wave.
And this is expected in normal patients.
And then as with varying levels of disease, you see
that the first thing you lose is the amplitude.
And that reflective wave starts to disappear
with more disease, even less amplitude.
And then with very severe levels of disease,
the waveform starts to round out
until eventually when there's very, very severe disease,
the waveform will actually be flat.

And again, there's a series of advantages, with the PVR.
Again, very easy to learn, very easy to perform, quick
and very easy to interpret, as I'll show you in a second.
It allows for the assessment of global, limb profusion.
You can evaluate at the level of the metatarsal
as well as at the digits.
And the great thing in this is
because you don't have to compress the vessel,
the PVR waveform is not affected, by,
calcified arteries.

And here in a patient with significant disease on the left,
we see that, you can very quickly distinguish
between normal and abnormal.
By simply looking at the shape
and the height of the wave forms, you can very quickly,
decipher this patient that there's significant disease on
the left patient's, relatively normal on the right.

Then you can do more critical evaluation
by looking at the height as well
as the shape of the waveform.
You can put all this information together.
You can look at the pla, the plasmo graphic results.
You can look at the pressure measurements,
and you can get a pretty good idea about
how severe the disease is, as well
as a general idea about the level of disease,
especially when you put it all together,
with the pulse examination, as well
as the presenting symptoms.

So here we're looking at the two waveforms.
In fact, on your left, a nice normal phasic waveform.
And then on the right, what you might not expect in a normal
situation, unless of course you knew what the patient,
that the patient had actually exercised.
And this in fact, is a normal response to exercise.
As you know, you get a vasodilatory effect with exercise,
where at the arteriolar level, the, arterio, dilate
resistance is decreased, and
therefore you have a significant decrease, increase
in diastolic flow.

And in fact, this is the rationale here.
This is the principle that's involved in patients
with exercise testing.

Exercise Testing

There will be a subset of patients who are,
are symptomatic with exercise, who in fact will have normal
resting pressures and normal resting pvs.
Well, this group of patients really deserves
to have exercise testing, to elucidate what's going on.
And in many cases, you can uncover a stenosis,
within the arterial system
that in fact is not symptomatic at rest.

And the principle is that as you
increase the flow across the stenosis,
because the distal resistance is decreased,
you will cause turbulence
and a significant, drop in pressure.
And again, that is the rationale for exercise testing.

Exercise testing is beneficial
because it allows us to differentiate true vascular
claudication, from other,
pseudo claudication type symptoms.
And this is important in patients with combined,
neuropathy and, vascular disease.
And in when we use exercise testing,
we can determine which condition,
in fact is limiting the walking.

It's indicated again in patients
with exercise related leg symptoms
who have normal resting parameters.

Now, the ideal way to do exercise testing is
to use a treadmill.
We can put the patient on a treadmill at 1.5
or two miles per hour, typically at a 10% grade.
We will then ask the patient to walk.
Of course, this is after you've acquired all
of the resting parameters.
Typically what we do is we leave the ankle cuff on,
have the patient exercise,
wait till the patient become symptomatic,
and then very quickly acquire the post-exercise,
ankle pressures, and then monitor the
pressures for several minutes.

Now, in patients with, hemodynamically significant,
disease, which is not appreciated at rest,
if the disease in fact is,
or if the symptoms in fact are genic in origin,
what you should see is a significant drop in pressure.
If the patient becomes symptomatic,
but there's no significant drop in pressure,
you can attribute the symptoms to some other etiology.

Now, there are some contraindications to treadmill,
exercise if the patient has a questionable cardiac status.
If you have a resting, ankle brachial index of about 0.5
or below, if there's the presence of ischemic ulcerations,
if patients have, difficulty walking,
or if the symptoms occur only at rest,
then exercise testing is probably not in
indicated in these patients.

Now, the, again, the,
claudication criteria is any significant drop in ankle
pressure after exercise that would be greater than 20
millimeters of mercury or so.
An absolute pressure of less than 60 millimeters
of mercury all confirm a vascular etiology for claudication.

Now, there are some labs where you don't have the benefit
of having, a treadmill,
but there are some other options.
And you can do a test that is called postocclusive
reactive hyperemia.
Some people call that PORH.
And what we do in these cases is we'll do the arresting
examination, and then we'll have the patient continue
to lay down and we'll inflate the thigh cuff,
to a supra systolic pressure, typically to a pressure
that's 20 millimeters of mercury above the resting pressure.

There's some limitations to this examination.
One, it can be a very painful examination, and
therefore they might be poor patient acceptance
and poor patient, compliance.
But the idea here is to create a state
of temporary ischemia,
and that results from the occlusion
of the distal thigh cuff.
We leave that inflated for about three to five minutes
or so, or as long as the patient can tolerate it,
we then deflate, deflate the cuff
and remeasure the ankle pressure once the,
cuff has been deflated.

Again, if there's a significant decrease in pressure,
that points to the, the possibility that there's some,
hemodynamically significant
occlusive disease process going on there.

But there's a problem with the post occlusive reactive
hyperemia test, and that is,
we're not really sure in these patients,
although we can, uncover an occult, stenosis,
we may not in fact know whether
that stenosis is causing the patient's symptoms
because we really haven't reproduced the activity
that makes the patient symptomatic.
So treadmill testing really is ideal in these patients.

Another option is to do toe raises.
We can actually have the patient stand
and do a series of toe raises for about one,
to two minutes,
note when the patient becomes symptomatic,
and then go through the whole process again of measuring,
the post-exercise pressures
and then looking for, the changes
that would be consistent, with the presence of disease.

Now, again, the bigger the drop in pressure
and the longer time it takes to get back to baseline,
the more severe the disease process is.
PORH and to raises are options.
But again,
exercise treadmill testing really is the best
option in these patients.

Summary

So to summarize, physiologic testing allows us
to determine whether the patient's symptoms are due
to arterial disease or other causes.
In patients with, symptomatic,
exercise related leg pain,
they can determine the presence
of peripheral arterial occlusive disease
and tell us about, the severity of disease as well
as the general location.

And often it's the results of the physiologic tests combined
with the, patient's symptoms
that will determine the need for intervention.
Again, this being based on the overall profusion symptom
and patient's, other comorbidities in our facility,
all patients referred
for suspected peripheral arterial disease will have a
physiologic te uh, test.
After the physiologic test, confirms the presence
of PVD, we then will use the duplex in patients
where there's some intention to treat,
to map the lower extremity arteries.
We don't, at all go straight
to imaging in these patients.