The Cardiovascular-Mortality-Based Estimate for Normal Range of the Ankle–Brachial Index (ABI)

Background: The ankle–brachial index (ABI) is a first-line examination in cardiovascular risk evaluation. Since cut-off values for normal ABI vary, the aim of the present study was to identify the cardiovascular-mortality-based estimate for the normal range of the ABI. After determining the reference range for the ABI, the corresponding toe–brachial index (TBI) and toe pressure for normal ABI were analyzed. Methods: All consecutive non-invasive pressure measurements in the vascular laboratory of a large university hospital 2011–2013 inclusive were collected and combined with patient characteristics and official dates and causes of death. Patients with an ABI range of 0.8–1.4 on both lower limbs were included in this study. Results: From 2751 patients, 868 had bilateral ABI values within the inclusion. Both ABI category ranges 0.80–0.89 and 0.90–0.99 had poorer survival compared to ABI categories 1.00–1.29 (p < 0.05). The 1-, 3-, and 5-year cardiovascular-death-free survival for respective ABI categories 0.80–0.99 vs. 1.00–1.29 were 90% vs. 96%, 84% vs. 92%, and 60% vs. 87%. The 1-, 3-, and 5-year overall survival for ABI categories 0.80–0.99 vs. 1.00–1.29 were 85% vs. 92%, 75% vs. 83%, and 42% vs. 74%. Conclusions: Borderline ABI (0.90–0.99) associates with higher overall and cardiovascular mortality compared to ABI values 1.00–1.29.