Background: The purpose of this study is to define the differences of predictors of ischemic heart failure (IHF) in Korean patients with acute myocardial infarction (MI). Methods: Clinical characteristics analysis was performed in total 11,581 patients from the Korea Acute Myocardial Infarction Registry, who were divided into two groups according to the initial left ventricular ejection fraction (LVEF): goup 1 (LVEF<40%, N=2271) and group 2 (LVEF≥40%, N=9310). Differences in clinical characteristics were compared between the groups and 1-year major adverse cardiac events (MACE) were analyzed in group 1. Results: Average LVEF were 33.0±6.4% in group 1 and 55.9±14.1% in group 2. Group 1 showed higher prevalence of male (p=0.02), Killip class>III (p=0.034), previous history of angina pectoris (p=0.001), hypertension (p=0.034), diabetes mellitus (p=0.027), smoking (p=0.045), age>65 years (p=0.015), systolic blood pressure<80 mmHg (p=0.033), heart rate>100 beats/min (p=0.027), elevated creatine, elevated cardiac markers (creatine kinase, CK-MB, troponin-I) (p=0.001), elevated total cholesterol (p=0.031), elevated triglyceride (p=0.022), and cardiac arrest on arrival (p=0.001). The predictors of 1-year MACE in group 1 were high N-terminal pro-B-type natriuretic peptide (NT pro-BNP) (p=0.001), multivessel disease(p=0.001), cardiogenic shock (p=0.02), and elevated creatine (p=0.024). Conclusion: Korean patients with acute MI and initial IHF were older; more likely to have multiple risk factors and comorbidities including cardiogenic shock and cardiac arrest on arrival. The predictors of 1-year MACE in patients with IHF were high NT pro-BNP, multivessel disease, cardiogenic shock, and acute kidney injury. Acute Myocardial Infarction Registry Investigators.