Ankle-Brachial Index

What You Need to Know

The ankle-brachial index (ABI) is a non-invasive diagnostic test used to determine your risk of peripheral artery disease (PAD). PAD is a condition where the arteries in your legs or arms become narrowed or blocked, increasing the risk of stroke, poor blood circulation, heart attack, and leg pain. The ABI test compares the blood pressure in your ankles with the blood pressure in your arms. A low ABI value indicates a narrowing of the peripheral arteries.

Why You Might Need an Ankle-Brachial Index Test

The ABI test is typically recommended for the following reasons:

To diagnose the severity of PAD

To monitor the effectiveness of treatments for PAD, such as medications, exercise,
angioplasty, or surgery

How the Ankle-Brachial Index Test is Performed

The ABI test is performed at your doctor’s office and requires no special preparation. Here’s what you can expect during the procedure:

1. Preparation: You will lie on a table, and your doctor will use a standard blood pressure cuff to measure the pressure in your arms and in two arteries near each ankle.

2. Measurement: A stethoscope or a hand-held ultrasound device may be used to hear the pulse.

3. Calculation: The ABI is calculated by dividing the highest blood pressure at the ankle by the highest blood pressure in the arms. The test can be performed both at rest and after exercise.

Understanding Your ABI Test Results

The results of the ABI test help determine the condition of your arteries. A normal ABI value at rest ranges from 1.0 to 1.4, indicating no significant narrowing or blockage of the peripheral arteries. Here’s a breakdown of what different ABI values suggest:

ABI of 0.9 to 0.99: Some narrowing of arteries, indicating the early stages of PAD.

ABI of 0.8 to 0.89: Early stage of PAD.

ABI of 0.5 to 0.79: Moderate blockage of ankle or leg arteries, likely causing leg pain during exercise.

ABI of less than 0.4: Severe PAD.

ABI of more than 1.4: Stiff arteries, which may require further evaluation.

For patients with diabetes or chronic kidney disease, the standard ABI test may not be accurate due to calcification (hardening) of the arteries. In such cases, measuring blood pressure at the less rigid arteries of the toe can provide more accurate results.

By understanding the ankle-brachial index and its implications, you can better assess your vascular health and take necessary steps to manage or treat peripheral artery disease.