 Coronary microvascular dysfunction is highly prevalent in revascularized ST-elevation myocardial infarction and has important prognostic implications. Current data suggest that ticagrelor might be superior to prasugrel in the reduction of coronary microvasculature dysfunction. Thus, we have designed a clinical trial that will compare microvascular function in revascularized ST-elevation myocardial infarction patients at treatment steady state with ticagrelor or prasugrel. Coronary microvascular dysfunction will be assessed with the index of microcirculatory resistance after primary percutaneous coronary intervention and at 1 month follow-up in the infarct-related vessel and non-infarct related vessel. 