The ankle-brachial index (ABI) is a noninvasive diagnostic test used to determine an individual's risk for peripheral artery disease, or PAD. It can also help determine the severity or progress of the disease if it has already been diagnosed. This test is done by comparing the blood pressure in the ankle with the blood pressure in the arm. Since PAD is a condition that involves a narrowing or blockage of arteries in the leg, a low ankle-brachial index may indicate narrowed arteries in the legs. The ankle-brachial index is an important test since PAD is a dangerous condition which can lead to heart attack or stroke.
Candidates for Ankle-Brachial Index
Individuals may have risk factors for PAD, making the probability of developing the disease more likely. These risk factors may include:
- Being age 50 or older
- Being a current or former smoker
- Being overweight
- Having diabetes
- Having high blood pressure
- Having high cholesterol
Individuals who have poor circulation, experience leg pain and/or have other risk factors for PAD, should have an ankle brachial index test performed.
The Ankle-Brachial Index Procedure
The ankle-brachial index is a simple, safe and non-invasive procedure with no risks or side effects. Sometimes this test is performed in conjunction with two other procedures that check for blocked or narrow arteries elsewhere in the body: a carotid ultrasound and an abdominal ultrasound. The ankle-brachial index evaluates blood flow in a patient complaining of leg or arm pain, numbness, tingling and fatigue, all of which are symptoms of narrowing, hardening and blockage of the arteries. Doppler technology uses sound waves to detect blood flow, and identify any differences in blood pressure, in the arms and legs. During the arterial Doppler ultrasound, a transducer is used to detect blood flow before and after a blood-pressure cuff is inflated. Patients may experience mild cramping because the cuffs cut off circulation. ABI using Doppler ultrasound usually takes about 45 minutes to perform, and patients can return to their regular activities immediately afterwards.
Carotid Artery Ultrasound
A carotid artery ultrasound is a diagnostic procedure that uses high-frequency sound waves to generate images of the neck's internal carotid arteries, which supply oxygen-rich blood to the brain. A carotid artery ultrasound is used to evaluate a patient's risk of stroke or other cardiovascular complications by checking for artery-narrowing plaque buildup.
In general, candidates for carotid artery ultrasound are those who are at high risk for, or beginning to display the symptoms of, carotid artery disease. Candidates include those who have recently had a stroke or carotid artery surgery; have an abnormal sound in, or damage to the walls of, a carotid artery; or are suspected of having blood clots in a carotid artery. High-risk candidates for carotid artery disease include those who have been diagnosed with diabetes or high cholesterol, or have a family history of heart disease.
During the ultrasound procedure, the patient lies faceup on a table, and a doctor applies a cool gel to both sides of the neck, at each artery's location. A transducer is moved over the arteries to give off sound waves; the sound waves' echoes bounce off the artery walls and blood cells, and are converted into images by a computer. The images, usually in black and white, are then displayed on a computer screen. If a Doppler ultrasound is included in the test, the flow of blood through the arteries can be detected; blood flow is usually shown in color. A carotid artery ultrasound is performed in a doctor's office, and usually takes less than 30 minutes.
There are no risks associated with a carotid artery ultrasound, and patients can return to their regular activities immediately afterward. Results are discussed with the patient shortly after the ultrasound is completed.