Introduction: The ankle-brachial index (ABI) is known as a predictor of future limb events. However, little is known about the optimal ABI cut-off value for future major adverse limb events (MALE) in patients with peripheral artery disease (PAD). The aim of this study was to evaluate the ability of ABI to predict MALE in PAD patients.
Methods: The IMPACT-ABI study was a retrospective, single-center, cohort study that enrolled and obtained ABI measurements for 3131 patients hospitalized for cardiovascular disease between January 2005 and December 2012. From this cohort, we identified 444 patients with PAD (ABI ≤ 0.9). Based on receiver operating characteristic (ROC) analysis, patients were divided into two groups: ABI ≤ 0.6 (31%) and 0.6 < ABI ≤ 0.9 (69%). We defined MALE as major/minor amputation and a new onset of CLI. The primary outcome measure was MALE. The secondary outcome measure was MACE defined as a composite of all-cause death, myocardial infarction and stroke.
Results: Over a mean follow-up of 3.8 years, 36 MALE occurred. The incidence of MALE was significantly higher in patients with ABI ≤ 0.6 than in those with 0.6 < ABI ≤ 0.9 (21.3% vs. 11.0%, log rank P = 0.015). There were no significant difference in incidence of MACE between both groups (53.4% vs. 58.3%, log rank P = 0.657). In multivariate Cox proportional hazard analysis, ABI ≤ 0.6 was an independent predictor of MALE (hazard ratio: 2.17; 95% confidence interval: 1.11 - 4.22; P = 0.023).
Conclusions: ABI ≤ 0.6 was an independent predictor for major/minor amputation and a new onset of CLI in patients with PAD. This study suggests that patients with ABI ≤ 0.6 especially need careful clinical follow-up for future limb events.