The new angiography evaluation will be done if necessary. The study population will consist of at least 100 patients who presented within 12 hours after the onset of chest pain, who had ST-segment elevation of more than 0.1 mV in two contiguous leads, and for whom the clinical decision was made to treat with percutaneous coronary intervention (PCI). Following confirmation of eligibility criteria, patients will be randomized in a 1:1 ratio to receive prophylactic infusion of Vitamin C or Placebo. The coronary angiograms will be assessed at a core laboratory with Quantitative Coronary Angiography.