The presence and severity of peripheral arterial disease evaluated by blood pressure in arm and leg and character of leg symptoms helps to identify patients at highest risk for functional declines in walking endurance, according to a study in the July 28th issue of the Journal of the American Medical Association..

According to background information in the article, cross-sectional studies demonstrate that distinct types of leg symptoms reported by patients with peripheral arterial disease in the lower extremities are associated with varying degrees of functional impairment. Severity of peripheral disease as measured by the ankle brachial index is also associated with degree of functional impairment. However, relationships between ankle brachial index, leg symptoms, and functional decline are as yet unknown.

A patient is tested for peripheral arterial disease by measuring blood pressure at the ankle and in the arm while the person is at rest, and then repeating both measurements after five minutes of walking on a treadmill. Ankle brachial index is calculated by dividing the blood pressures measured in the lower leg by the blood pressure measured in the arm. A normal resting index is greater than 1.00 or 1.10, and a decrease in index with exercise or a resting index of < 0.90 are sensitive indicators that significant peripheral disease is probably present.

Mary McGrae McDermott, MD, and her American colleagues conducted a prospective cohort study among 417 people with peripheral disease and 259 without it. The participants were age 55 and older and had baseline functional assessments between October 1, 1998, and January 31, 2000, with follow-up assessments scheduled one and two years afterward. In the current study, peripheral arterial disease was defined as ankle brachial index less than 0.90, and participants with peripheral disease were categorized at baseline into one of five mutually exclusive symptom groups.

The researchers measured annual changes in six-minute walk performance and in usual-paced and fast-paced four-meter walking velocity, adjusted for age, sex, race, prior-year functioning, coexisting diseases, body mass index, cigarette smoking, and patterns of missing data.

“Among 676 men and women age 55 years and older, participants with low ankle brachial index levels at baseline had significantly greater decline in walking endurance at two-year follow-up, compared with those with normal baseline ankle brachial index levels,” the authors wrote. “Participants with indices less than 0.50 at baseline had a nearly 13-fold increased risk of becoming unable to walk for six minutes continuously two years later, relative to participants with indices of 1.10 to 1.50.”

Baseline leg symptoms among participants with peripheral disease also predicted rates of functional decline. “Participants with peripheral disease having leg pain on exertion and rest experienced greater declines in walking endurance and walking speed than did individuals without peripheral disease,” the authors write. “Participants with asymptomatic peripheral disease had significantly greater declines in six-minute walk performance than did participants without peripheral disease.”

“Previously reported lack of worsening in claudication symptoms over time in patients with peripheral arterial disease may be more related to declining functional performance than to lack of disease progression,” they suggested.

“Our findings underscore the importance of using the ankle brachial index to identify persons with peripheral arterial disease, since it is frequently undiagnosed or asymptomatic,” the authors concluded. “Further study is necessary to develop treatments to prevent functional decline in patients with peripheral disease who do not have classic intermittent claudication.”