Aim: Statin decreases low density lipoprotein cholesterol level and prevents atherosclerosis. Although statin may be beneficial for patients with acute myocardial infarction (AMI) due to its direct anti-atherosclerotic effect, statin is not usually prescribed to all patients with AMI. This study was performed to identify different determinants of statin treatment and its prognostic impacts in patients with AMI according to their baseline LV systolic function. Methods: 12,988 patients with AMI were enrolled into nationwide registry database study. Patients were stratified into 2 groups according to their LV ejection fraction (LVEF): LVEF < 40% vs ≥ 40%, and determinant factors for statin treatment and MACE were identified in each group. Major adverse cardiovascular events (MACE) within 12 months of AMI including death, nonfatal MI and revascularization were assessed. Results: 1,962 patients (15.1%) with LVEF < 40% were older and had more un¬favorable cardiovascular risk factors than those with LVEF ≥ 40%. ...