Background: Acute Heart Failure (AHF) complicates acute Myocardial Infarction (AMI) as a result of complex interaction of structural, hemodynamic, neurohormonal, and genetic maladaptations. This study aims to analyse the role of Left Atrial Volume Index (LAVI) compared to other conventional parameters of systolic and diastolic Left Ventricular function (LV) in patients with first time ST Segment Elevation Myocardial Infarction (STEMI), in predicting in-Hospital Heart failure (HF), in-hospital mortality and development of heart failure and subsequent rehospitalisation over a followup period of 6 months. Material and Methods: The present study is a prospective observational study conducted in the Cardiology Department of Assiut University Hospitals (AUH) on 70 STEMI patients admitted to Coronary Care Unit (CCU). Left Ventricular Ejection Fraction (LVEF), LV End-Systolic and End-Diatolic Dimensions (LVESD and LVEDD), LAVI, diastolic and systolic parameters were measured within 24 hours after admission and then 6 months later. These variables were correlated with the development of heart failure according to Killip classification on admission and 6 months later by NYHA classification. Results: There was a statistically significant difference regarding development of in-hospital HF (Killip classification >II) with the following variables LAV, LAVI, LVESD, FS, EF, and the diastolic parameters used to evaluate diastolic function except Isovolumetric Relaxation Time (IVRT) and E/A ratio, whereas in-hospital mortality was related significantly to the same variables except LAVI, E/A ratio and EF by univariate analysis. (p-value <0.001). After 6 months of follow-up, there was a statistically significant relation between mortality development and the following variables; LAVI, EF, Deceleration Time (DT), IVRT, TDI (tissue Doppler imaging) septal e` and E/e` by univariate analysis. (p-value <0.001).