Multifactorial determinants of functional capacity in peripheral arterial disease: uncoupling of calf muscle perfusion and metabolism

The ankle-brachial index is associated with the magnitude of impaired walking endurance among men and women with peripheral arterial disease

Previous reports suggest that the severity of peripheral arterial disease (PAD), measured by the ankle-brachial index (ABI), is not associated with the magnitude of walking impairment, measured by treadmill testing. These prior studies have had small sample sizes and included only PAD participants with symptoms of intermittent claudication. We studied the association of the ABI with diverse measures of walking performance in a cross-sectional study of 156 participants with PAD with and without intermittent claudication symptoms. Outcomes included the Gardner-Skinner treadmill test, 6-minute walk, 4-meter walking velocity at usual and fastest pace, and the walking impairment questionnaire (WIQ). Adjusting for age, sex, race, comorbidities, leg symptoms, and other confounders, lower ABI values were associated with shorter distance achieved in the 6-minute walk (ABI < 0.50: 286 meters; ABI 0.50-0.70: 316 meters; ABI 0.71-0.95: 355 meters, p trend < 0.001), shorter maximal treadmill walking time (ABI < 0.50: 6.0 minutes; ABI 0.50-0.70: 6.9 minutes; ABI 0.71-0.95: 8.3 minutes, p trend = 0.009), and lower WIQ distance scores (p trend = 0.007) among PAD participants. The ABI was not associated significantly with walking velocity over 4 meters, treadmill time to onset of leg symptoms, or the WIQ speed or stair-climbing scores. In conclusion, among 156 participants with PAD with and without intermittent claudication, lower ABI values are associated significantly with poorer walking endurance, assessed by three distinct measures. Clinical Trial Registration - URL: http://www.clinicaltrials.gov. Unique identifier: NCT00106327.