Ankle Brachial Index

Peripheral vascular disease is a problem that affects many of our patients. In the USA it is estimated to affect 8-10 million people and the numbers are growing. Identifying patients with PVD is important, as PVD is a risk marker for a number of conditions, including: coronary disease, cerebrovascular disease, aneurysmal disease, diabetes, and hypertension. Having documented PVD increases the risk of cardiovascular mortality 4-6 times over healthy age-matched individuals.

A simple and useful test to assess lower extremity arterial perfusion is the ankle-brachial index (ABI). This test can be easily performed using a handheld Doppler device and a blood pressure cuff.

The proper technique to use is as follows:

1. Place the patient in the supine position and measure the brachial pressure in both arms using the Doppler device. The higher of the two reading is the one you will use to calculate the Index. There should be a difference of less than 10 mm Hg between each brachial pressure measurement.


2. Place the blood pressure cuff on the patient's leg just above the malleoli. Measure the anterior tibial and posterior tibial arterial systolic pressures. Select the higher of these two values as the ankle pressure measurement to be used as the ankle systolic pressure in the ABI calculation.


3. To obtain the ABI, divide the ankle systolic pressure by the brachial systolic pressure.

Interpreting the results

ABIs as high as 1.10 are normal; abnormal values are those less than 1.0. The majority of patients with claudication have ABIs ranging from 0.3 to 0.9. Rest pain or severe occlusive disease typically occurs with an ABI lower than 0.50. Indexes lower than 0.20 are associated with ischemic or gangrenous extremities.

Knowing the ABI is of particular importance if you wish to apply a pressure dressing to treat a venous leg ulcer. An ABI of less than 0.6 to 0.8 is a contraindication to such a dressing as it increases the risk of further ulceration.

It is also important to remember that stiff or calcified arterial walls, such as those seen in patients with diabetes (a group frequently associated with venous ulceration), may give a falsely high ABI. In these cases it would be wise to be guided by a higher ABI before applying the dressing, or consult a vascular specialist, if one is available.

Many family physicians do not have office access to a Doppler device. In this situation it may be possible for the nurses in the Out Patient Department to do the procedure prior to applying the bandage. It would not be a bad idea to insure that the nurse is following the appropriate protocol in measuring the ABI.

- John Hickey

Thanks to Dr. R. Lewanczuk, Director Division of Endocrinology and Metabolism University of Alberta Edmonton, AB for reviewing the draft copy of this article.

1. Consensus Statement Developed by the Standards Division of the Society of Interventional Radiology. David Sacks, MD, Curtis W. Bakal, MD, MPH, Peter T. Beatty, MD, Gary J. Becker, MD, John F. Cardella, MD, Rodney D. Raabe, MD, Harvey M. Wiener, DO, and Curtis A. Lewis, MD, MBA J Vasc Interv Radiol 2003; 14:S389


2. Ankle-Brachial Index: Calculating Your Patient's Vascular Risk. Sloan H, Wills EM. Nursing99; 1999:29(10):58-- 9; and Sieggreen MY, Maklebust J. Managing Leg Ulcers. Nursing96;1996:26(12):41-6.

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