Introduction: Acute STEMI is the most serious presentation of CAD. Restoration of the coronary flow facilitates cardiomyocyte salvage and decreases cardiac morbidity and mortality. However, reperfusion may result in paradoxical cardiomyocyte dysfunction, a phenomenon termed reperfusion injury. Trimetazidine is a metabolic anti-ischemic drug which is beneficial in reducing periprocedural myocardial reperfusion injury. The aim of the work is to study the effect of trimetazidine on myocardial salvage index in patients with acute STEMI who underwent primary PCI. Methods: Forty patients presented with acute STEMI, underwent primary PCI with injection of an intravenous dose of Tc-99m labeled Sestamibi before primary PCI then first set of SPECT images were taken within 6 h from injection time to assess the initial size of the perfusion defect. Prior to discharge the patients received another dose of Tc-99m labeled Sestamibi and follow up SPECT images were taken to assess the final perfusion defect and to calculate myocardial salvage and myocardial salvage index. Twenty patients of them received trimetazidine before primary PCI (study group) and the other twenty patients did not receive trimetazidine (control group). Results: (1) Patients with acute STEMI undergoing primary PCI who received trimetazidine before primary PCI had better myocardial salvage index, however it was statistically non significant. (2) Statistically significant better myocardial salvage index with post procedural TIMI 3 flow than with post procedural TIMI 2 flow among patients who received trimetazidine before primary PCI. Conclusion: In the presence of post procedural TIMI3 flow trimetazidine is beneficial in improving myocardial salvage index in patients presented with acute STEMI who underwent primary PCI.