Introduction: The main aim in the management of acute myocardial infarction (MI) is to establish early restoration of coronary flow in order to preserve viable myocardium, primary percautaneous coronary intervention (PCI) has been documented to be superior to other reperfusion strategies in terms of remodeling, preservation of left ventricular (LV) function and mortality reduction. (1) Decreased LVEF and LV function are associated with poor prognosis. Therefore, early identification of high-risk patients is crucial. (2) Aim of the work: This study was designed to evaluate the predictive value of tissue Doppler Echocardiography (TDI) for LV ejection fraction measured by conventional Echocardiography in ST-elevation MI patients who underwent primary PCI in reference to ejection fraction and infarct size measured by technetium Tc99m sestamibi single photon emission computed tomography. Methods: 50 patients were included in the study, they were subjected to full history taking and clinical examination. Electrocardio-graphic analysis, cardiac biomarkers sampling and primary percutanous coronary intervention. Echocardiographic studies were performed within 24 hr and 3 month of the acute infarction. Technetium Tc 99m sestamibi were pefrmed 3 months after primary PCI. All patients of the study were divided into 2 groups: Group (I): included 39 patients with positive invasive and non invasive criteria of reperfusion. Group (II): included 11 patients with negative invasive and non invasive criteria of reperfusion.