Ankle-Brachial Index Test
Overview
The ankle-brachial index (ABI) measures blood flow to the legs. Healthcare professionals use this test to identify peripheral artery disease (PAD), a condition that narrowed arteries cause. PAD can result in leg pain while walking and is linked to a higher chance of heart attack and stroke. Clinicians calculate the ABI by comparing blood pressure at the ankle and the arm.
If the number is lower than normal, it may suggest a blockage or limited blood flow in the leg arteries. Sometimes, clinicians perform an exercise version, which involves walking on a treadmill before repeating the test. Many vascular specialists and cardiovascular societies recommend ABI testing to catch PAD early, support diagnosis, and help guide treatment plans.
Reason for the Test
The ankle-brachial index test finds blocked or narrowed arteries in the legs, which may point to peripheral artery disease (PAD). People who often feel pain in their legs while walking, or have risk factors like diabetes, high cholesterol, high blood pressure, or a history of smoking, may need this test. Atherosclerosis, or plaque build-up in the arteries, also increases risk.
Why Doctors Order This Test:
- Check for PAD and related vascular disease.
- Help prevent heart attack or stroke.
- Decide if treatments like angioplasty, surgery, or revascularization are needed.
| Risk Factors | Related Conditions |
|---|---|
| High Cholesterol | Peripheral Arterial Disease |
| Diabetes | Stroke |
| High Blood Pressure | Heart Attack |
| History of Smoking | Atherosclerosis |
Potential Concerns
During the ankle-brachial index test, the blood pressure cuffs can cause brief discomfort or mild pain in the arms and legs as they inflate. This pain usually goes away once the cuff is released.
Special Considerations
- People with diabetes or calcified blood vessels may face added challenges during the test.
- If someone has severe pain, healthcare professionals may recommend alternative tests like imaging.
Possible Risks and Concerns
| Risk Area | Details |
|---|---|
| Discomfort | Temporary pain from the cuffs |
| Underlying conditions | Diabetes, vessel calcification may affect results. |
| Cardiovascular risk | Test may hint at a higher risk for heart events. |
| Rare issues | Severe pain may require a different testing method. |
Paralysis or lasting effects are uncommon.
Getting Ready for the ABI Test
No special steps are needed before an ankle-brachial index (ABI) test. People should wear loose, comfortable clothes so that a blood pressure cuff can be placed on their arm and ankle. This makes it easier for the clinician or podiatrist to do vascular testing and use a Doppler instrument for the exam. Basic foot care is not required before testing.
Checklist
- Loose sleeves and pants.
- Easy access to ankles and upper arms.
- No need to fast before the test.
What You Might Experience
While the Test Is Happening
- The person rests for 5 to 10 minutes before the test begins.
- They lie comfortably on a table, face up.
- The healthcare worker places blood pressure cuffs on both arms and ankles.
- The healthcare worker uses a hand-held ultrasound tool to listen to blood flow in the arteries after releasing the cuffs.
- This process checks systolic blood pressure and pedal pulses in the ankles.
Once the Test Is Finished
- The ankle-brachial index test usually lasts only a few minutes.
- People do not need to recover or limit activities afterward.
- The healthcare professional explains what the results mean, such as if there is any sign of poor blood circulation, leg pain, or claudication linked to conditions like ischemia in the distal extremities.
Outcomes
The ankle-brachial index (ABI) test checks blood pressure at both the ankle and arm, then compares the two numbers to find a ratio. This value helps doctors figure out how well blood is moving through the leg arteries.
Table: ABI Values and Their Meanings
| ABI Range | What It Suggests | Possible Next Steps |
|---|---|---|
| 1.0–1.4 | Arteries are open; normal flow | No PAD, further testing if symptoms exist |
| 0.90–0.99 | Possible early artery narrowing | Borderline PAD, exercise ABI may be advised |
| Less than 0.90 | Narrowed or blocked arteries | PAD diagnosis, further imaging or testing |
When the ABI value falls in the normal range (between 1.0 and 1.4), this points to healthy arteries. If someone’s ABI is lower (0.90 to 0.99), the arteries could be starting to narrow. Values below 0.90 strongly suggest the presence of peripheral artery disease (PAD).
In some cases, especially among people with advanced diabetes or severe artery disease, measuring blood pressure at the toe (toe brachial index) can provide a more precise result if the ABI test does not give accurate information.
Doctors base treatment recommendations on the ABI result, severity, and symptoms. They may advise changes in daily habits, increased physical activity, medication, or possibly surgery to improve blood flow.
