Background and Objectives:The role of coronary stenting in the treatment of patients with small vessels (<3.0 mm) in AMI is not well defined. The purpose of this study was to investigate the influence of vessel size on the long-term clinical and angiographic outcome following primary stenting in AMI. Subjects and Methods:The study comprised 130 AMI patients with successful primary stent implantation within 12 hours of chest pain onset. Patients were divided into two groups according to the vessel size of the infarct related artery, with the respective ranges of the groups being <3.0 and ≥3.0 mm. The primary end points were the major adverse cardiac events including death, recurrent myocardial infarction, or target vessel revascularization at follow-up. The incidence of angiographic restenosis (≥50% of diameter stenosis) was assessed as a secondary end point. Results:Event-free survival in the small vessel group (less than 3mm of reference vessel diameter) was 62.5% at 23.7±13.0 months and 76% in the large vessel group (p<0.001) at 23.5±12.0 months. The follow-up angiographic restenosis rate was significantly higher in the small vessel group (61% vs. 32% in the small and large vessel groups, respectively, p=0.026). Conclusion:Acute myocardial infarction patients with small vessels present a higher risk for an adverse outcome following primary stenting. (Korean Circulation J 2002;32(3):233-240)