What is Ankle-Brachial Index?
The ankle-brachial index (ABI) is a simple, rapid, non-radiological,
non-invasive and highly valuable test that can be easily performed
in the clinic to analyse your risk of peripheral artery disease.
The ABI test can:
Diagnose Peripheral Arterial Disease and prevent its progression
and complications
Identify people who have a high risk for coronary artery disease
What is Peripheral Artery Disease (PAD)?
PAD is a serious condition where the arteries of lower extremities are narrowed or blocked due to build-up of cholesterol in the arterial walls resulting in poor circulation or restriction of flow of oxygen-rich blood. People with PAD are at increased risk of heart attack and stroke.
This condition may occur in about 4% in the healthy adult population over the age of 40 years old to as high as 30% in patients in patients who undergo screening in a primary care setting with diabetes, cigarette smoking and age as risk factors.
What is Peripheral Artery Disease (PAD)?
It is recommended to have ABI test done if you are at risk for peripheral arterial disease.
Things that can increase your risk for PAD include:
Diabetes
Being older than age 70
High levels of lipids or cholesterol in your blood
Known plaque formation in other arteries, like the coronary arteries in your heart
Abnormal pulses in your lower legs
Being younger than age 50, with diabetes and one additional risk factor, such as smoking or high blood pressure
It is also recommended to have an ABI test if you have symptoms of PAD, like pain in the legs with activity. But not everyone with PAD has symptoms. This makes the test even more important. ABI yearly test can monitor any existing PAD to see if your condition is getting worse.
If you’ve had surgery on the blood vessels of your legs, your doctor might request an ABI test done to see how well blood is flowing into the leg. Sometimes healthcare providers use ABI to assess your risk of future heart attack or stroke.
How is ABI obtained?
ABI is derived from ratio of measuring and comparing the systolic blood pressure of the lower extremities (leg) at the ankle region to the systolic blood pressure at the upper arm (brachial region). The severity of peripheral arterial disease can therefore be determined by using this ratio also called the index number. The lower the index, the more severe the condition. Of special important is a ABI index of less than 0.9. It indicates lower blood pressure at the ankle compared to the arm and implies that there is narrowing or blockage of the arteries in the legs. See the table for the more insight into ABI index value:
Ankle Brachial Index Number
| 1.0 to 1.4 | = | normal (because the pressure between the lower extremities (leg) and arm should be almost the same or a little higher in the lower extremities). |
| 0.99 to 0.91 | = | borderline; considered for additional cardiovascular risk testing |
| ≤0.9 to 0.8 | = | mild PAD |
| ≤0.8 to 0.5 | = | moderate PAD |
| <0.5 | = | severe PAD |
| >1.4 | = | rigid or hardened artery which are not compressible |
What equipment is used to measure ABI?
At Phoenix Podiatry, we use cutting edge ABI measurement system, that includes four cuffs that are used at the same time.
The index is calculated automatically by the system with a high degree of reliability and bypassing human error in calculation.
Based on volume plethysmography technology, which is superior
to other automatic systems using the oscillometric method,
our ABI ability system is able to detect ankle pressures as low as 55mmHg and ABI as low as 0.29. It also has patented double cuffs design to increase reliability to the next level.
How do I get ready for an ankle brachial index test?
There is very little you need to do to prepare for an ABI test. You can follow a normal diet on the day of the test. You shouldn’t need to stop taking any medicines before the procedure.
You may want to wear loose, comfortable clothes. This will allow the technician to easily place the blood pressure cuff on your arm and ankle
What happens during an ankle brachial index test?
The test is very similar to a standard blood pressure test. In general, during your ABI test:
- You will lie flat during the procedure.
- A podiatrist will place four blood pressure cuffs to take pressure measurements from the pulses located in your arms and legs.
- The cuffs will tighten once all is set and a podiatrist will press an activation button on our ABI system. The test will take approximately 3 minutes to complete. Pressure from cuffs may be a little uncomfortable, but it won’t hurt. You need to stay relaxed, remain still and refrain from talking, coughing etc.
- Next, the ABI system will calculate your ABI index.
- Podiatrist will inform you on your results straight away and will advise on your next step depending on the results.
What happens after an ankle brachial index test?
You should be able to go back to your normal activities right after your ABI test.
Be sure to follow up with your doctor about your results if the results are abnormal. In some cases, you may need follow-up testing to get more information about a blocked vessel. This might include an MRI or an arteriogram.
What are possible treatments for PAD?
If you have PAD, you may need treatment. Possible treatments include:
Stopping smoking
Treating high blood pressure, high cholesterol, and diabetes, if needed
Staying physically active
Eating a healthy diet
Taking medicine to increase blood flow to your legs or to prevent blood clots
Having procedures to restore blood flow, like angioplasty
Having surgery to your leg (if the blockage is severe)
