Background: Left atrial (LA) volumetric assessment by echocardiography remains a simple, non-invasive technique for left atrial functional assessment.
Objective: The aim of the current work was to assess the left atrial function and its relation to the severity of the lesion in-hospital course in patients with ST-segment Elevation Myocardial Infarction(STEMI) undergoing Primary Percutaneous coronary intervention (PCI).  
Patients and Methods: This cross-sectional study included a total of 135 patients with acute STEMI, attending at Department of Cardiology, Zagazig University Hospitals. The included subjects were categorized into two groups; Group 1 included those, who developed adverse events. (31 patients “23%"), and Group 2: included patients with benign course. (104 patients “77%"). Coronary angioplasty as well as Echocardiography were done to all patients.
Results: Regarding the echocardiographic parameters, there were significant differences between both study groups as regards Wall motion score index, left atrium volume index, Left atrium expansion index, LA total ejection fraction and E/e′ ratio. There was no significant difference between the two groups regarding LVEF. There was a high significant correlation between left atrial volume index and Wall Motion Score Index, Syntax score, Left atrium expansion index, LA total ejection fraction and E/e′ ratio. On a multivariate model for independent predictors for hospital adverse events were High syntax score, Left atrium volume index and Left atrium expansion index.
Conclusion: It could be concluded that LA functions has high significant correlated with the severity of the lesion and a good prog
nostic factor in hospital course of STEMI patients undergoing primary PCI.