OBJECTIVE: to evaluate the safety and efficacy of a brief intracoronary infusion of ADO applied at the time of reperfusion to limit infarct size and LV remodelling in patients with ACSST submitted to primary ACTP. DESIGN: Multicentric, prospective, randomised, parallel, placebo-controlled double-blind study. PATIENTS: 200 patients older than 18 with ACSST and without prior myocardial infarction receiving primary PTCA within 6 hours after symptom onset.