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Harvard Heart Letter | October 2008
Ankle-brachial index
Comparing blood pressure at the arm and ankle can reveal peripheral artery disease.
Arteries
that deliver blood to parts of the body below the heart don’t get
nearly as much attention as the coronary arteries that supply the heart
or the carotid arteries that supply the brain. They should. These
so-called peripheral arteries are anything but peripheral. They’re
central to good health for the kidneys, intestines, and legs. They are
also prone to the same damaging processes that stiffen and clog
coronary arteries. Peripheral artery disease causes suffering,
disability, and sometimes death among the millions of Americans who
have it.
A key test for problems in the peripheral arteries is a blood pressure measurement known as the ankle-brachial index.
Why it is done
In
a perfectly healthy circulatory system, blood pressure measured at the
brachial artery in the crook of the arm (which is near the heart) is a
good gauge of blood pressure elsewhere in the body. But when blood must
travel through stiff or cholesterol-clogged arteries, the pressure at
sites further from the heart can differ from that in the arm. The
ankle-brachial index, sometimes called the arm-ankle index, compares
blood pressure from two locations. A large difference between the two
can signal the presence of peripheral artery disease. The test can also
track the progression of the disease or the effect of treatment.
Who needs it?
Anyone
with symptoms of peripheral artery disease should have an
ankle-brachial index test. The most common sign of this condition is
pain or cramping in the calves, thighs, hips, or buttocks when walking,
climbing stairs, or exercising that fades with rest. Doctors call this
claudication. Wounds on the toes, feet, or legs that don’t heal or take
a long time to heal are another sign. So is a leg that feels cooler to
the touch than other parts of the body, or that looks to be a different
shade.
Peripheral artery disease, like coronary artery
disease, often doesn’t cause symptoms until it is advanced. So an
ankle-brachial index is also recommended for people at high risk of
developing the disease. This includes smokers or former smokers over
age 50; adults with diabetes, high blood pressure, or high cholesterol;
those who have had a stroke or mini-stroke; and anyone with a strong
family history of heart disease.
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