The Impact of Post Stenting Balloon Dilatation on Coronary Microcirculation in STEMI Patients Undergoing PPCI

Inclusion Criteria * \>18 years of age * Acute symptoms onset with duration \> 20 minutes * ST-segment elevation ≥ 0.1 mV in ≥ 2 contiguous leads, signs of a true posterior infarction or documented newly developed left bundle branch block * Infarct related artery with a diameter above 2.5 mm * Operator's intention to proceed to stent deployment (i.e. not refer for CABG or defer PCI) Exclusion Criteria * \< 18 year of age * Symptoms duration \> 12 hours * Unable to give informed consent * Previous bypass graft surgery * Previous myocardial infarction * Pregnancy * Known severe chronic kidney disease (creatinine clearance ≤30 mL/min), unless the patient is on dialysis * Unable to receive antiplatelets or anticoagulation (i.e. coagulation disorders, bleeding etc.) * Haemodynamic instability * Severe LMS disease * Culprit vessel diameter \< 2.5 mm * Contraindications to adenosine * Any study lesion characteristic resulting in the expected inability to deliver OCT catheter to the lesion pre and post PD (e.g. moderate or severe vessel calcification or tortuosity)