3. OVERALL DESIGN AND PLAN OF THE STUDY 3.1. OVERVIEW OF STUDY FLOW The RIGENERA 2.0 trial is a phase II placebo-controlled, randomized, open label, with Blinded Evaluation of end-points. One hundred and twenty STEMI patients are planned to be enrolled in 4 Italian centers (Rome - Catholic University of the Sacred Heart, Ferrara, Pisa and Padua). Patients with an acute ST-elevation myocardial infarction as defined by the universal definition of AMI undergoing acute revascularization (i.e. either acute PCI within 24 hours of symptom onset or thrombolysis within 12 hours followed by acute PCI within 24 hours of symptom onset) will be screened at investigational sites. Patients who had acute PCI at institutions different from the investigational sites (recruiting centers) can also be included: interested patients may be referred for screening to any of the participating study sites within 3 to 4 days. Informed consent and assessment of eligibility of patients with respect to in- and exclusion criteria will be done at the recruiting centers. If all other eligibility criteria are met, echocardiography will be performed 3 to 6 days after the acute PCI and ejection fraction will be quantified. In case of LVEF≤45% the patient will be 1:1 electronically randomized to G-CSF and MCE or placebo and MCE according to site. Patients will be randomized to receive either subcutaneous Granulocyte - Colony Stimulating Factor (group 1) or Placebo (group 2) both added on top of optimal standard of care and Myocardial Contrast Echocardiography with intravenous infusion of sulphur hexafluoride.