Association Between Intra-Leg Ankle-Brachial Index Asymmetry and Major Adverse Limb Events in Patients with...

Background/Objectives: The ankle-brachial index (ABI) is the gold-standard test for peripheral artery disease (PAD). However, ABI is conventionally calculated using the higher of the dorsalis pedis (DP)- or posterior tibial (PT)-derived ankle pressure values, which may mask clinically relevant differences between arterial territories within the same limb. We assessed whether intra-leg ABI asymmetry was associated with adverse limb outcomes in patients with PAD. Methods: A total of 2495 patients with PAD attending outpatient vascular clinics were retrospectively analyzed. Intra-leg ABI asymmetry was defined as an absolute difference ≥0.15 between DP- and PT-derived ABI values within the same leg. The primary outcome was 2-year major adverse limb events (MALE), defined as major amputation or lower extremity revascularization. Associations between intra-leg ABI asymmetry and outcomes were evaluated using multivariable logistic regression models adjusted for age and sex. Results: Overall, 1077 (43%) patients had intra-leg ABI asymmetry. Over 2 years of follow-up, MALE occurred more frequently in patients with intra-leg ABI asymmetry compared to those without (17.2% vs. 7.2%, p < 0.001). Patients with intra-leg ABI asymmetry also had higher rates of revascularization (13.9% vs. 5.8%, p < 0.001) and major amputation (8.2% vs. 2.3%, p < 0.001). In multivariable analysis, intra-leg ABI asymmetry remained independently associated with 2-year MALE (adjusted OR 2.49, 95% CI 1.92-3.23, p < 0.001). Conclusions: Clinically significant intra-leg ABI asymmetry was common and independently associated with adverse limb outcomes in patients with PAD. These findings suggest that DP-PT ABI discordance may provide important prognostic information beyond conventional ABI reporting methods.