Ankle-Brachial Index, a New Predictor for All-Cause Mortality

Abstract

Dear editor,We read with great interest the article entitled "Predictive Value of the Ankle-Brachial Index for All-Cause and Cardio-Cerebrovascular Mortality" by Xu et al. 1 We congratulate the authors and would like to discuss some points about the relationship between ankle-brachial index (ABI) and cardiovascular (CV) disease (CVD).Xu et al. divided participants into 4 groups according to the quartile of ABI. 1 They found the association between levels of ABI and the risk of all-cause mortality was L shaped: The level of ABI associated with the lowest risk of mortality was 1.11, and a lower ABI below 1.11 increased the risk of mortality. They concluded that ABI was negatively associated with all-cause mortality when ABI ≤1.11.A study of 941 patients revealed that ABI calculated using mean blood pressure had a predictive value for overall and CV mortality. 2 Similarly, Lin and colleagues 3 included 2160 diabetic patients ≥30 years and demonstrated that ABI is a predictor of all-cause and CV mortality. Interestingly, Ikura et al 4 studied 102 Japanese diabetic patients, with a mean age of 63 years, and reported that ABI was not a predictor for all-cause mortality in diabetic patients after lower extremity amputation. The inconsistencies between these studies may be explained in part by differences in studied populations, sample size, and definitions.Ankle-brachial index, calculated as the ratio of the highest systolic pressure in the tibial artery to the highest systolic pressure in the brachial artery, is a marker of peripheral arterial disease. 5 An ABI of <.9 is a noninvasive and low-cost method to diagnose peripheral artery disease. The mechanisms by which ABI affects mortality remain unclear. We infer that the real mechanisms may be multifactorial.