Post-Exercise Ankle-Brachial Pressure Index Demonstrates Altered Endothelial Function in the Elderly

BACKGROUND: The ankle-brachial pressure index (ABI), the ratio of the systolic blood pressure of the ankle to the systolic brachial pressure, is commonly measured at rest, but ABI values post-exercise enhance the sensitivity of the test and can be used to identify atherosclerotic vascular damage. However, it has not been established whether or not enhanced post-exercise ABI is also associated with endothelial dysfunction. We hypothesized that a decrease in post-exercise ABI is related to impaired endothelial function. PURPOSE: To investigate alterations in post-exercise ABI values and endothelial dysfunction in the elderly. METHODS: The study population comprised 35 men and women aged 51-77 years (mean age: 66 years). Patients with peripheral arterial disease or a history of heart failure were excluded. The ABI was estimated at rest and immediately after exercise. The exercise protocol comprised 2.5 min of active pedal flexion exercises at a speed of 60 times/min. Endothelial function was assessed by measuring flow-mediated vasodilation (FMD) in the brachial artery using ultrasound imaging. RESULTS: No correlation was found between FMD and the ABI at rest. However, a weak correlation was found between FMD and post-exercise ABI (r = 0.46, P = 0.06). A strong correlation was observed between FMD and a decrease in post-exercise ABI compared to baseline readings (r = -0.52, P = 0.01). Multiple linear regression analysis was used to generate a prediction equation for FMD using the percentage decrease in post-exercise ABI. Significant correlations were observed between the ultrasound imaging-measured FMD and the predicted FMD (R(2) = 0.27, P = 0.001). CONCLUSIONS: Post-exercise ABI appears to be a simple surrogate marker for endothelial function in the elderly, although larger studies are required for validation.