Background: Low ejection fraction after acute myocardial infarction (AMI) can lead to an increased risk of in hospital mortality. But little is known about the risk factors for in hospital mortality after AMI with low ejection fraction admitted to coronary care unit (CCU). The aim of the present study was to evaluate the predictors of in hospital mortality after AMI with low ejection fraction admitted to CCU. Methods: 176 patients (123 males, 64.8 짹 13.2 year-old) after AMI with low ejection fraction (EF<45%) admitted CCU were enrolled from Jan 2006 to May 2008. Clinical and coronary angiographic characteristics, echocardiography, and laboratory examination were evaluated. The patients were divided into the two groups according to survival in coronary care unit. Results In hospital mortality was 5.1%. In-hospital mortality was more frequently associated with patient with stroke history (33.3% vs. 6.6%, p=0.026), Killip class III-IV(55.5% vs 20.4%, p=0.005), increase of heart rate (112.33짹30.57 vs. 87.1짹20.12, p<0.001), not underwent PCI (44.4% vs. 80.2%, p=0.024), use of IABP (44.4% vs 8.4%, p=0.001), use of ventilator (55.6% vs 6.0%, p<0.001). In Cox proportional hazard analysis, history of stroke [Hazard ratio (HR); 12.024 95% CI=2.287-63.210, p=0.003), increased of heart rate (HR; 1.047 95% CI=1.014-1.082, p=0.005) and use of ventilator (HR; 16.14 95% CI=3.598-72.478, p=0.0005) were independent predictors of in hospital mortality after adjustment for clinical, angiographic, laboratory data. Conclusions: History of stroke, increased heart rate, use of ventilator were associated with increased in-hospital mortality after AMI with low ejection fraction admitted to CCU.