Paradox of the Relationship between Cardio-Ankle Vascular Index and Ankle-Brachial Index in Patients with Lower Extremity Artery Disease

Objectives: Measurements of ankle-brachial index (ABI) and toe-brachial index (TBI) are standard examinations for evaluating arterial blood flow in lower extremities and diagnosing lower extremity artery disease (LEAD). It remains to be clarified whether cardio-ankle vascular index (CAVI), a blood pressure-independent parameter of arterial stiffness, is associated with ABI and TBI in patients with LEAD. Methods: The subjects were 165 outpatients with LEAD. Arterial blood flow in lower extremities was evaluated by using ABI, TBI, and the degree of leg exercise-induced reduction of ABI (%). Results: CAVI showed significant positive correlations with ABI and TBI and showed significant inverse correlations with exercise-induced % decrease in ABI. CAVI was significantly higher in the 3rd tertile groups of ABI and TBI than that in the corresponding 1st tertile groups and was significantly lower in the 3rd tertile group of exercise-induced % decrease in ABI than that in the 1st tertile group. The above relationships remained significant after adjustment for age, body mass index, blood pressure, diabetes history, and habitual smoking. Conclusions: Although CAVI is a general parameter reflecting arterial stiffness, CAVI showed paradoxical associations, namely positive associations with ABI and TBI and an inverse association with exercise-induced % decrease in ABI in patients with LEAD.