Peripheral arterial disease (PAD), assessed through ankle-brachial index (ABI), reflects systemic atherosclerotic burden and may predict coronary artery disease (CAD) complexity and clinical outcomes in ST-elevation myocardial infarction (STEMI). Limited data exist from Southeast Asian populations regarding PAD prevalence and prognostic significance in acute myocardial infarction patients.

We conducted a retrospective analysis of consecutive STEMI patients who underwent primary percutaneous coronary intervention (PCI) and ABI measurement at the Central Chest Institute of Thailand from January 2020 to December 2024. PAD was defined as ABI <0.90 in either lower extremity. Primary endpoints included major adverse cardiovascular events (MACE) and all-cause mortality during structured follow-up visits.

Among 1,128 STEMI patients, PAD prevalence was 14.2% (n=160). PAD patients were significantly older (64.0±13.4 vs. 59.5±12.0 years; P<0.001) with markedly reduced ABI values (right: 0.898±0.141 vs. 1.131±0.119; left: 0.919±0.131 vs. 1.145±0.118; both P<0.001). Left ventricular ejection fraction was comparable between groups (51.7±14.0% vs. 52.0±12.6%; P=0.776). Multivessel CAD prevalence was numerically higher in PAD patients (66.3% vs. 63.6%; relative risk 1.04, 95% CI 0.93-1.17; P=0.607). PAD patients demonstrated significantly elevated mortality (7.5% vs. 1.1%; relative risk 6.60, 95% CI 2.96-14.70; P<0.001) and MACE rates (9.4% vs. 2.3%; P=0.009). A stepwise increase in adverse outcomes was observed across ABI severity categories (normal→mild→moderate PAD; P<0.001 for trend).

PAD affects approximately one in seven STEMI patients in this Thai cohort and identifies a high-risk subgroup with substantially increased mortality and cardiovascular events. Routine ABI assessment may enhance risk stratification and guide intensive secondary prevention strategies in STEMI patients undergoing primary PCI.