The goal of primary PCI is to restore anterograde myocardial flow. Stenting a largely thrombotic lesion may determine distal embolisation of thrombotic material therefore deteriorating myocardial perfusion.

In the setting of largely thrombotic lesions such as those treated in the context of primary PCI, stenting often results in distal micro and macro-embolisation which hampers coronary flow and microvascular recovery. Interestingly in some of these studies comparing BMS versus balloon angioplasty an early hazard associated to the use of stent has been reported.

Thus, investigators hypothesize in this protocol that refraining from stenting during the acute phase of ST segment myocardial infarction is safe and associated to improved myocardial recovery as compared to acute stenting.

Inclusion Criteria:

• chest pain for >30 min with ST-segment elevation of one mm or more in 2 or more contiguous ECG leads or with presumably new left bundle-branch block
• admission either within 12 h of symptom onset or between 12 and 24 h with evidence of continuing ischaemia

Exclusion Criteria:

• the exclusion criteria will include history of bleeding diathesis or documented allergy/intolerance or contraindication to clopidogrel or ticlopidine or prasugrel
• inability to assume an oral P2Y12 receptor blocker on a consecutive daily basis for a minimum of 6 months, or to heparin or aspirin
• uncontrolled hypertension (systolic or diastolic arterial pressure >180 mmHg or 120, respectively, despite medical therapy)
• limited life expectancy, e.g. neoplasms, others
• inability to obtain informed consent
• pregnancy
• patients were not enrolled if they were clinically unstable, presented with severe arrhythmia, or had known contraindications to CMR (claustrophobia, pacemakers, or implantable defibrillator devices)