Association of Asymptomatic Low Ankle–Brachial Index with Long-Term Clinical Outcomes in Patients after Acute Myocardial Infarction

Aims: Peripheral arterial disease (PAD) is the well-known risk factor for cardiovascular events. Although low ankle–brachial index (ABI) is recognized as a risk factor in general population, low ABI without any symptoms of PAD has not been established as a prognostic marker in patients with acute myocardial infarction (AMI) yet. The purpose of this retrospective study was to examine whether asymptomatic low ABI was associated with long-term clinical outcomes in AMI patients without treatment history of PAD. Methods: We included 850 AMI patients without a history of PAD and divided them into the preserved ABI (ABI ≥ 0.9) group (n=760) and the reduced ABI (ABI ＜0.9) group (n=90) on the basis of the ABI measurement during the hospitalization. The primary endpoint was the major adverse cardiovascular events (MACE) defined as the composite of all-cause death, non-fatal myocardial infarction, and hospitalization for heart failure. Results: During the median follow-up duration of 497 days (Q1: 219 days to Q3: 929 days), a total of 152 MACE were observed. The Kaplan–Meier curves showed that MACE were more frequently observed in the reduced ABI group than in the preserved ABI group (p＜0.001). The multivariate COX hazard analysis revealed that reduced ABI was significantly associated with MACE (hazard ratio 2.046, 95% confidence interval 1.344–3.144,p=0.001) after controlling confounding factors. Conclusions: Reduced ABI was significantly associated with long-term adverse events in AMI patients without a history of PAD. Our results suggest the usefulness of ABI as a prognostic marker in AMI patients irrespective of symptomatic PAD.