Lower ankle/brachial index, as calculated by averaging the dorsalis pedis and posterior tibial arterial pressures, and association with leg functioning in peripheral arterial disease

Objective: We compared three commonly used methods of ankle/brachial index (ABI) calculation to determine their relative association with objective me asures of leg functioning in peripheral arterial disease. Method: The study design was cross-sectional; the setting was an academic m edical center. The participants were 244 men and women, aged 55 years and o lder, with and without peripheral arterial disease, from a noninvasive vasc ular laboratory and a general medicine practice. The main outcome measures were walking velocity and endurance, measured with the 4-m walk and the 6-m inute walk, respectively. Three methods of ABI calculation were assessed: u sing the highest arterial pressure within each leg (method #1), using the l owest pressure in each leg (method #2), and averaging the dorsalis pedis an d posterior tibial pressures within each leg (method #3). for each method, we established the prevalence of peripheral arterial disease. We then used regression analyses to identify the ABI calculation method most closely ass ociated with leg functioning. The ABI with the greatest statistical signifi cance and largest regression coefficient was considered most closely associ ated with leg functioning. Results: Peripheral arterial disease prevalence ranged from 47% when method #1 was used to 59% when method #2 was used. When the right and left legs w ere compared, the leg with the lower ABI, as identified through use of meth od #3, was most associated with leg functioning. Within the leg with the lo wer ABI, method #3 was more closely associated with 6-minute walk distance (regression coefficient = 811.5 feet per 1 unit ABI; P < .001) and 4-m walk ing velocity (regression coefficient = 0.353 m/s per 1 unit ABI; P < .001) than method #1 or method #2. Conclusion: The lower ABI, determined by averaging the dorsalis pedis and p osterior tibial arterial pressures in each leg, is most predictive of walki ng endurance and walking velocity in. peripheral arterial disease.