The investigators previously reported that angioplasty postconditioning reduces infarct size (cardiac enzyme release) in STEMI patients with a fully occluded coronary artery at hospital admission. Animal studies have suggested that the time window for applying brief episodes of ischemia and reperfusion aimed at triggering postconditioning's protection is very narrow, i.e. does not expand beyond 1 minute after reflow. We sought to address whether this window might be larger in humans, i.e. whether STEMI patients might be protected several minutes after undergoing spontaneous reperfusion before admission coronary angiography.

Therefore, STEMI patients (onset of chest pain less than 12 hours) with a TIMI flow grade > 1 were eligible for that study. Angioplasty postconditioning was completed as already published and infarct size was assessed by measuring cardiac enzymes release.

Inclusion Criteria:

• Patient > 18 years old
• Male or female
• Presenting first myocardial infarction, with the beginning of pains < 12 hours,
• Requiring a revascularisation by primary angioplasty or " rescue " (after failure of thrombolysis) on LAD or RCA (not Circumflex coronary artery).
• TIMI flow grade at admission of 2 or 3
• LV angiography (RAO30°) before angioplasty.

Exclusion Criteria:

• Cardiac arrest before the angioplasty
• Cardiogenic shock
• Occlusion of the artery circumflex responsible for the infarction
• Visible collaterals to the area at risk
• Magnetic resonance imaging: contra indication