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 longterm 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.