Ankle Brachial Index - Blood Pressure in the Lower Extremity and Peripheral Artery Disease
Peripheral artery disease causes suffering, disability, and sometimes death among the millions of Americans who have it. A useful way to detect problems in the peripheral arteries is a blood pressure measurement known as the ankle-brachial index.
Comparing blood pressure at the arm and ankle can reveal peripheral artery disease. Peripheral arteries are essential to good health for the kidneys, intestines, and legs. They are also prone to the same damaging effects that hardenand clog coronary arteries. .
In a healthy circulatory system, blood pressure measured at the brachial artery in the crook of the arm (which is near the heart) is a good indicator 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.
Symptoms of PAD (peripheral artery disease) include pain or cramping in the calves, thighs, hips, or buttocks when walking, climbing stairs, or exercising that fades with rest. 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. However PAD, 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.
To test for peripheral artery disease, blood pressure is measured in two arteries that supply the foot using a blood-pressure cuff and an ultrasound probe. It can be done in a doctor's office and doesn't require any preparation other than removing your shoes and socks. Using a standard blood pressure cuff measurements of the pressure in the posterior tibial artery and the dorsalis pedis artery near each ankle are taken and recorded. The highest pressure recorded at the ankle is divided by the highest pressure recorded at the brachial artery. This gives the ankle-brachial index.
The normal range for the ankle-brachial index is between 0.90 and 1.30. An index under 0.90 means that blood is having a hard time getting to the legs and feet: 0.41 to 0.90 indicates mild to moderate peripheral artery disease; 0.40 and lower indicates severe disease. The lower the index, the higher the chances of leg pain while exercising or limb-threatening low blood flow.An ankle-brachial index over 1.30 is usually a sign of stiff, calcium embedded arteries.
The ankle-brachial index can offer significant information about general cardiovascular health.