AIMS: To study the prognostic importance of left ventricular systolic function in patients with heart failure (HF) and acute myocardial infarction (AMI) with respect to the presence of prior heart failure and known ischemic heart disease. METHODS: In 13,084 consecutive patients diagnosed with either AMI or HF, a medical history and an echocardiographic assessment of left ventricular systolic function by wall motion index (WMI) were obtained. Patients were divided into four groups: AMI with or without a history of HF, and primary HF (no recent AMI) with or without a history of ischemic heart disease (IHD). Mortality was assessed after nine years of follow-up. RESULTS: WMI stratified patients according to all-cause mortality in all four groups of patients (p<0.0001). For a decrease in WMI of 0.3 (corresponding to a decrease in left ventricular ejection fraction of 0.1), the hazard ratio was 1.61 (95% CI: 1.48-1.76) for AMI patients without prior HF, 1.43 (1.38-1.48) for AMI patients with prior HF, 1.26 (1.22-1.30) for primary HF patients with IHD and 1.23 (1.18-1.27) for HF patients without IHD. CONCLUSION: WMI stratifies patients with IHD and/or HF according to risk of all-cause death. The presence of HF attenuates the prognostic power of WMI.