Associations between Peripheral Arterial Disease and Leg Function

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The summary below is from the full report titled "The Ankle Brachial Index Is Associated with Leg Function and Physical Activity: The Walking and Leg Circulation Study." It is in the 18 June 2002 issue of Annals of Internal Medicine (volume 136, pages 873-883). The authors are MM McDermott, P Greenland, K Liu, JM Guralnik, L Celic, MH Criqui, C Chan, GJ Martin, J Schneider, WH Pearce, LM Taylor, and E Clark.

What is the problem and what is known about it so far?

The blood vessels that carry blood from the heart to the legs are called peripheral arteries. Sometimes, fatty buildup in the artery walls reduces or blocks blood flow through these arteries, a condition called peripheral arterial disease (PAD). Slightly more than 10% of Americans older than 65 years of age have PAD. The condition is more common in people who smoke or have high cholesterol levels or diabetes mellitus. Peripheral arterial disease reduces blood supply to tissues. It can cause pain in one or both calves that is present during walking and is relieved by rest (intermittent claudication). Some people with PAD do not have symptoms or leg pain. Many experience changes in leg function that affect their ability to walk.

A way to detect PAD is to get an ankle brachial index (ABI), which compares blood pressure in the arm and lower leg; PAD is diagnosed if the blood pressure in the lower leg is lower than in the arm (ABI < 0.90). Because ABI is a simple, noninvasive way to identify PAD, it allows us to study large numbers of people and to better define the types of symptoms and dysfunction associated with PAD.

Why did the researchers do this particular study?

To describe symptoms and leg function in people with PAD.

Who was studied?

740 adults (460 with and 280 without PAD) from three academic medical centers in the Chicago, Illinois, area.

How was the study done?

All patients answered questions about leg symptoms and had ABI tests to detect the presence or absence of PAD. Then, they underwent several tests that measured leg function, including a 6-minute walk test, repeated chair stands, a standing balance test, and a test of walking speed. At the time the leg function tests were performed, the patient and the researchers who gave the tests did not know the results of the patient's ABI.

What did the researchers find?

Of 460 people with PAD (ABI < 0.90), only 152 (33%) had symptoms of intermittent claudication. Compared with people who had normal ABIs, those with abnormal ABIs had worse lower-extremity function, including slower velocity, an inability to maintain a tandem stand, an inability to walk continuously, and coverage of a shorter distance during a 6-minute walk.

What were the limitations of the study?

The ABI is not 100% accurate in detecting PAD. Moreover, most of the participants with PAD were recruited from special laboratories where patients are referred specifically because PAD is suspected. People with unrecognized PAD may have different findings than people who are specifically referred for diagnostic evaluation of PAD.

What are the implications of the study?

Peripheral arterial disease is associated with impaired lower-extremity function, and many patients with PAD do not have symptoms of intermittent claudication.