Background: Coronary artery disease is considered a major cause of death in both male and female subjects in the developed world and carries a risk of several complications. Multiple scores have been developed in order to set risk stratification and predict the outcomes for ischemic patients. Another scores have been developed in order to assess the severity of the coronary arteries lesions. Methods: The prospective cross sectional cohort study included 68 consecutive patients with STEMI; they were divided into two groups based on the shock index at presentation. Group A: included 43 patients with SI ˂0.7. Group B: included 25 patients with SI ˃ 0.7. All participants were subjected to trans-thoracic echocardiography, PPCI, SYNTAX score calculation and follow up during the hospitalization period. Results: There was a significant myocardial damage in group B supported by the reduced LVEF and elevated serum troponin at presentation. There was a significant more coronary artery lesion severity in group B as assessed by the SYNTAX score. As regard in-hospital outcomes, patients in group B had the worst outcomes during the hospitalization period. Conclusions: Shock index is a useful and quick tool to predict the severity of the underling coronary artery disease and correlate with the SYNTAX score in patients with STEMI. Shock index is a good indicator of the hemodynamics and the extent of myocardial damage. Shock index is a quick bedside tool with a good prediction value for the in-hospital outcomes in STEMI patients undergoing PPCI.