Ankle–brachial pressure index

An index used to measure peripheral artery disease

The Ankle–Brachial Pressure Index (ABPI) is a simple, non-invasive test used to assess the presence of peripheral artery disease (PAD). It compares the blood pressure in the ankle with the blood pressure in the arm.

Diagram illustrating the measurement of the Ankle–Brachial Pressure Index

Measurement

The ABPI is calculated by dividing the systolic blood pressure at the ankle by the systolic blood pressure in the arm. The procedure involves the following steps:

1. The patient is asked to lie down in a supine position.
2. A blood pressure cuff is placed around the arm to measure the brachial systolic pressure using a Doppler ultrasound device.
3. The same procedure is repeated at the ankle, measuring the systolic pressure at the posterior tibial artery and the dorsalis pedis artery.
4. The highest of the two ankle pressures is used to calculate the ABPI.

Interpretation

The ABPI is interpreted as follows:

• 1.0 to 1.4: Normal
• 0.9 to 1.0: Acceptable
• 0.8 to 0.9: Some arterial disease
• 0.5 to 0.8: Moderate arterial disease
• < 0.5: Severe arterial disease

A low ABPI indicates reduced blood flow to the limbs, suggesting the presence of peripheral artery disease. An ABPI greater than 1.4 may indicate stiff arteries, which can occur in conditions such as diabetes mellitus or chronic kidney disease.

Clinical Significance

The ABPI is a valuable tool in the diagnosis and management of peripheral artery disease. It helps in assessing the severity of the disease and in monitoring the effectiveness of treatment. A low ABPI is associated with an increased risk of cardiovascular disease and stroke.

Limitations

While the ABPI is a useful screening tool, it has limitations. It may not be accurate in patients with calcified arteries, such as those with diabetes or advanced age, where the arteries are non-compressible. In such cases, additional tests like toe-brachial index or imaging studies may be required.

Related pages

• Peripheral artery disease
• Doppler ultrasound
• Cardiovascular disease