Arterial Blood
Flow Studies of the Legs (Segmental Doppler Pressures)
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What is the
test?
People who have leg pain when exercising may
need an evaluation to make sure they have normal
blood flow through their leg arteries. Normally
blood pressure is similar whether it is measured
in the legs or in the arms. If blood pressure
is lower in the legs, it usually means that cholesterol
buildup inside the leg arteries is interfering
with circulation. By taking accurate blood pressure
measurements at different locations along your
legs, your doctors can determine if you have
any arterial narrowing and, if so, where.
In order to get accurate blood pressure measurements,
your doctor uses a technique called Doppler ultrasound.
Doppler ultrasound is a painless way to detect
blood flowing through a small artery. It uses
sound waves and a type of sonar detection system
to make noise when blood flow is detected. For
arterial studies of the legs (called segmental
Doppler pressures), Doppler ultrasound is used
in place of the stethoscope that doctors usually
use when taking blood pressures.
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How
do I prepare for the test?
You may want to wear shorts for this exam, and
your feet should be bare during the test. If
you are not wearing shorts, you may have to change
into a hospital gown.
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What
happens when the test is performed?
You lie on a table and a technician or doctor
wraps blood pressure cuffs around one of your
legs in four or five locations (including the
thigh, calf, and ankle). He or she then squirts
some clear jelly onto your skin to help the Doppler
sensor (which resembles a wand or pen) slide
around easily and to help conduct sound waves
through your skin.
Each blood pressure cuff is inflated two times.
The first time, the cuff is only inflated part
way so that it exerts a gentle pressure on your
leg. The cuff sends information to a computer
about the size of your leg and how elastic your
arteries seem to be as the pressure is increased.
A wavy line that signifies your blood flow appears
on a video screen.
The second time, each cuff is inflated to exert
more pressure on your leg. This temporarily cuts
off circulation in the leg. Many patients briefly
experience some cramping pain in the calf or
thigh (similar to the sensation you experience
when a blood pressure cuff is inflated around
your arm). As the cuff is deflated, the doctor
places a Doppler sensor against your foot to
detect the moment when blood flow starts up again.
(When it does, you will hear a noise that sounds
like your heartbeat.) Checking the air pressure
of the deflating cuff at this time shows the
leg blood pressure.
After all the cuffs on one side have been tested,
the other leg is checked in the same way. For
comparison, you also have your blood pressure
checked in each arm using the Doppler Technique.
The whole test usually takes 45 minutes.
Some patients have their leg pressures checked
both before and after exercise. If this is the
case for your test, you are asked to walk on
a treadmill for a short time and then have the
test again afterward. The exercise version of
this test takes more time.
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What
risks are there from the test?
There are no risks.
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Must
I do anything special after the test is over?
The jelly will be wiped off. You will have no
side effects from the test.
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How
long is it before the result of the test is
known?
Your doctor should receive a formal report within
a few days.
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