13. PAD(Peripheral Arterial Disease)'s Diagnosis
Several tests may be required
to diagnose PAD and determine the extent of the disease. Some of these tests may
be performed in a primary care physician's office, whereas others may be
performed by a vascular specialist or in a vascular lab. Most tests are
non-invasive and thus should be fairly painless.
▣ Medical History and Physical Exam
▣ Ankle-brachial index (ABI)
▣ Treadmill Exercise Test
▣ Reactive Hyperemia Test
▣ Segmental Pressure Measurements
▣ PVR Waveform Analysis
▣ Duplex Arterial Imaging or Ultrasound Imaging
▣ Photoplethysmography (PPG)
▣ Arteriogram
1. Medical History and Physical Exam
A thorough physical exam is
necessary to begin to look for signs of PAD, to grade its severity, and to
determinethe best treatment. Your physician will ask for the following
information:
♣ Review your personal history
of leg or heart symptoms
♣ The medical review of
your family
♣ Whether you smoke and
how much
♣ Other risk factors
such as diabetes, high blood pressure and cholesterol levels
♣ Any symptoms you have
when you walk
♣ Any medications or
vitamins you are presently taking
Your doctor will also examine
you by:
♣ Listening to your heart
♣ Feeling your abdomen
♣ Assess your pulses at
various places, usually at the top of your legs, behind your knees, in the
groin, and at your ankles
♣ Examining your feet
Blood test: Your doctor may
request a blood test to look at your general health and to assess risk factors
that affect the development of PAD, including your fasting blood cholesterol
levels, your blood sugar, your kidney and liver function, and occasionally your
homocysteine levels.
2. Ankle-Brachial index (ABI)
The ankle-brachial index
(ABI) is a simple, reliable means for diagnosing PAD. Blood pressure measurements are taken at the
arms and ankles using a pencil shaped ultrasound device called a Doppler. A
Doppler instrument produces sound waves (not x-rays) and is considered
noninvasive because it does not require the use of needles or catheters. The
ABI test is simple enough to be performed in any doctor's office or vascular
laboratory. Not only is the ABI one of the most reliable tests for PAD, it is also
the least expensive.
You will be asked to lie on your back while standard blood pressure cuffs are placed around your ankles and arms. These cuffs will be inflated briefly above your normal systolic blood pressure. Once the cuffs are deflated, blood pressure measurements are taken using the Doppler instrument. The arm and ankle systolic blood pressure measurements are recorded. Then the ankle systolic pressures are divided by the highest arm pressure to establish an ABI measurement for each leg. The ABI range that is generally considered normal is 0.95 to 1.2.
Although the ABI is extremely
reliable, this test may not be accurate in all patients. Some patients with
long-standing diabetes, kidney disease, or some elderly patients, may have
rigid blood vessels. These may be difficult to compress with the blood pressure
cuff and, in these patients, the ABI reading may not be accurate.
For patients with rigid ankle
blood vessels, toe pressure measurements may be taken since toe arteries are
rarely rigid. This examination is called a toe brachial index (TBI) and is a
calculation based on the systolic blood pressures of the arm and the systolic
blood pressures of the toes. The
examination is similar to the ABI except that it is performed with a photoplethysmograph
(PPG) infrared light sensor and a very
small blood pressure cuff placed around the toe. A TBI of .8 or greater is considered normal.
Alternatively, a leg arterial ultrasound test can detect PAD if the ABI is not
considered reliable.
The ABI Exam
The ABI test is used to
document the presence or absence of PAD, and can be performed every year to
quickly assess whether PAD is getting worse. Obviously, treatment for the
disease tries to slow the rate at which
leg arteries become blocked.
The ABI can also predict how
severe an individual's atherosclerosis is and the risk of future leg problems
(such as development of future leg rest pain, poor healing of foot wounds, need
for leg bypass surgery, or amputation).
It can also predict the risk of future problems from atherosclerosis in
other parts of the body (such as heart attack and stroke). Lower ABI values are associated with a higher
risk. In fact, the ABI value can be an accurate predictor for patients with
coronary heart disease (such as the blood cholesterol value, coronary calcium
score, and C-reactive protein value).
An ABI value greater than
0.80 is rarely associated with short-term leg problems such as foot wounds or
amputation. Nevertheless, any evidence of PAD (where the ABI measurement is
less than 1.00) is associated with future risk of heart attack and/or stroke.
An ABI value between 0.40 ~
0.80 is moderately decreased and such patients often experience some symptoms
such as pain in the legs. Attention to foot care is extremely important to
prevent accidental injury or infection. Again, any evidence of PAD is
associated with future risk of heart attack and/or stroke! Serious efforts to
keep one's risk factors under control is essential to keep PAD from getting
worse.
An ABI value of less than
0.40 indicates severe PAD. Patients
should be extremely careful to avoid any foot injuries. Proper foot care may prevent development of
non-healing wounds, rest pain, or even gangrene. Usually, care from a vascular
specialist is required. The specialist will evaluate the risk and benefits to
improve leg blood flow through surgery or other interventions.
The ABI test approaches 95
percent accuracy in detecting PAD.
However, a normal ABI value does not absolutely rule out the possibility
of PAD for a few individuals. Some patients with a normal or near-normal ABI
results may have few symptoms suggesting PAD. A treadmill exercise or reactive
hyperemia test may be recommended to test further for the disease and the cause
of pain.
3. Treadmill Exercise Test
A treadmill exercise test
provides additional information to the doctor such as how severe your symptoms
may be. By walking on a treadmill for a
few minutes, this test tries to imitate the experience you may have walking at
home.
This test can be especially
helpful for individuals in whom there may be more than one cause of leg
symptoms with walking, such as from lumbar back or sciatic pain, nerve pain, or
joint diseases. This test can also help you and your doctor distinguish the
relative importance of PAD and other heart and lung symptoms to your difficulty
with walking. Treadmill exercise tests are also useful for patients that will
begin a formal exercise program to improve their claudication symptoms. By
monitoring the heart during the treadmill exercise, your physician can reassure
you that the heart is also receiving enough blood flow. This can offer reassurance that an exercise
program will be safe as you work to increase your walking capacity.
The test usually follows
these steps:
♣ A baseline measurement of
your arm and ankle blood pressures at rest is taken.
♣ You will then be asked
to walk slowly on a treadmill, typically for as long as you can comfortably
walkuntil your symptoms become too uncomfortable to continue.
♣ Lying down again, your
arm and ankle blood pressure measurements will be immediately repeated.
In individuals without
significant PAD, ankle pressures will remain the same or increase somewhat in
comparison to your resting blood pressures. However, in individuals with PAD
there is usually a drop in the ankle blood pressures and ABI values after
exercise. When leg symptoms occur without a drop in ankle blood pressures,
these symptoms are usually not caused by PAD.
4. Reactive Hyperemia Test
The reactive hyperemia test
is an alternative to the baseline, ABI or treadmill test. If you are unable to
walk on a treadmill due to heart problems or shortness of breath, the reactive
hyperemia test can be performed to diagnose PAD.
You will be asked to lie on
your back while standard blood pressure cuffs are placed around your thighs and
ankles. The thigh cuffs will be inflated above your normal systolic blood
pressure for three to five minutes. Once the thigh cuffs are deflated, the
ankle cuffs are inflated briefly above your systolic blood pressure, then
slowly deflated. Using the Doppler instrument, blood pressure measurements are
immediately taken at both your ankles.
A significant (50% or
greater) decrease in ankle blood pressure indicates there is a blockage in your
leg arteries and thus is a diagnosis of PAD.
5. Segmental Pressure Measurements
Segmental pressure
measurements are blood pressure measurements taken at multiple levels on the
leg.
It is similar to the ABI
test, with the addition of two or three additional blood pressure cuffs. These
additional cuffs are placed just below the knee and one large cuff or two
narrow cuffs are placed above the knee and at the upper thigh. These cuffs are
then inflated above your normal systolic blood pressure, and then slowly deflated.
Using the Doppler instrument,
blood pressure measurements are taken. The blood pressure at each cuff location
on your leg is noted in your physician's report. A significant drop in pressure
between two adjacent cuffs indicates a narrowing of the artery or blockage
along the arteries in this portion of your leg. This allows the vascular
technologist and doctor to identify more precisely the location of such
blockages in the arteries of your leg.
6. PVR Waveform Analysis
The doctor or non-invasive vascular
laboratory may perform blood flow waveform analysis. The Pulse Volume Recording
(PVR) method measures blood volume changes that occur in your legs.
Using cuffs similar to those
involved in segmental pressure testing, PVR cuffs are inflated, but only a
little. Instead of temporarily stopping the blood flow to determine your blood
pressure, the PVR cuff allows the blood to continue flowing through your leg.
As blood pulses through your arteries, your blood vessels expand causing an
increase or decrease in the volume of air within the cuff.
A recording device displays
these pulse volume changes as a waveform. The shape of the waveform gives the
doctor useful information about the blood flow in your legs. This test often is
more informative for patients with diabetes or whose arteries have become stiff
and hard to compress due to calcification.
7. Duplex Arterial Imaging or Ultrasound Imaging
Another waveform method used
by the physician or vascular laboratory is Doppler waveform analysis produced
from a pencil shaped ultrasound probe or within ultrasound-imaging equipment.
The Doppler probe will show blood movement in your arteries as a waveform that
looks similar to a heart EKG. The shape of the waveform gives the doctor useful
information about the blood flow at the location being examined.
This test uses high-frequency
ultrasound to visualize the anatomy and blood flow in legs. This is the same
type of instrument used to examine unborn babies, the size or structure of
abdominal organs, such as the gall bladder, or to evaluate the blood flow in
the neck and the carotid arteries. The name "duplex" comes from
combining the two meanings:
♣ the conversion of
ultrasound signals into sounds that you can hear and
♣ pictures that you can see.
The Doppler part of the test
works by sending a high-frequency sound (ultrasound) wave through a
transmitting gel into the body. This sound wave bounces off the layers of the
body, such as muscle, bone, blood vessels, and various organs. Each type of
body tissue absorbs ultrasound signals differently. For example, if you took a
tennis ball and bounced it on different surfaces, it would bounce differently. It
bounces high on a hard surface like cement, yet barely at all on a soft surface
such as grass. In a similar manner that bats and submarines use sound to see
were they are going, your vascular specialist uses ultrasound to see images of
your body.
You will be asked to lie on
your back. Water-based gel will be placed along segments on your legs. The
pencil shaped ultrasound probe will be placed in the gel to display a segment
of your artery. The doctor or technologist will move the probe slowly up and down
the arteries to see and hear the blood flow. Your legs may be repositioned to
allow a better view of the artery.
These images help to
determine if you have cholesterol plaque, narrowed arteries or blockages in the
blood vessels of your legs. In addition, most duplex imaging systems also show
the direction of your blood flow in color. This information allows the vascular
specialist to determine if the blood is flowing away (arterial) or toward
(venous) your heart.
8. Photoplethysmography (PPG) Exam
This system uses infrared
light to assess blood flow near the surface of the skin. It may be used to take a blood pressure in a
toe, or used for waveform analysis. Instead of a sound signal, the PPG uses
infrared light to produce a waveform. This may be used for people in whom the
ankle arteries have become stiff and hard to compress due to calcification, as
noted in the ABI section above (individuals with longstanding diabetes, kidney
disease, or some elderly individuals).
The examination is similar to
the ankle- brachial index except that it is performed using a PPG sensor and a
very small blood pressure cuff around the toe. While lying on your back, a tiny
probe is placed over one or more of your toes on each foot and waveforms
recordings will be displayed and blood pressure measurements taken. The
measurements are called a TBI and when it is at 0.80 (80% of an ABI of 1.00) it
is considered normal.
9. Arteriogram
Arteriography is a minimally
invasive test in which an arteriogram or "road map" of the arteries
is made. An arteriogram looks a lot like an x-ray and is used to plan or guide
treatments such as surgery, angioplasty, or stent placement.
You will be asked not to eat
for several hours prior to the exam so mild sedation can be given safely. You
may need to have some simple laboratory blood tests prior to the arteriogram.
Your physician will explain the procedure and answer any questions you might
have. Then you will go to a room with sophisticated imaging equipment. You will
be given medicines through an intravenous line to make you sleepy and
comfortable, and a sterile drape will cover you from your chest down. A tiny
tube or catheter is then placed into the artery in the upper portion of the
thigh after the skin is made numb. The catheter is then steered to its intended
destination inside your vascular system using x-rays for guidance. A clear
liquid called contrast dye is then injected through the catheter and a series
of pictures are taken. You will usually feel a mild warm "flush" when
the dye is injected. Pressure will be applied to the groin after the sheath is
removed in order to prevent bleeding from the artery.
After the procedure and a
short observation period, you may go home. Sometimes if a treatment with a
balloon or stent is performed you may stay in the hospital overnight.
These pictures or images can
be used to diagnose the cause of arterial blockage or to precisely guide an
angioplasty balloon or stent into place to treat a blockage. The arteriogram
may also be used to plan a surgical treatment such as a bypass graft.
An angioplasty balloon is a
tiny balloon mounted on a catheter or small tube. The balloon is positioned
into the blocked area of the artery and is used to stretch open the artery. A
stent is a tubular scaffolding of metal wire that is also mounted on a small
catheter. The stent is placed across a blockage and holds the artery open like
the hoops on a barrel. An important difference is that the stent stays in the
artery while the balloon is removed from the artery after it is used.
