The purpose of this study is to determine whether intracoronary injection of morphine chlorhydrate is effective to limit ischemia-reperfusion lesion during percutaneous coronary angioplasty in patients with acute myocardial infarction (AMI).

Inclusion Criteria:

1. Acute Myocardial Infarction less than 6 hours defined by

   1. prolonged chest pain (>15 min)

   2. in association with

      • ST elevation 1mm or more in two contiguous leads
      • or occurence of Q wave in three contiguous leads
      • or occurence of left bundle branch block

2. Culprit lesion eligible for percutaneous coronary intervention (PCI)

3. TIMI flow 0 before PCI

Exclusion Criteria:

1. Fibrinolysis
2. Allergy to morphine
3. Active epilepsy
4. Brain injury or intracranial hypertension
5. Previous AMI, coronary artery bypass graft (CABG)
6. Cardiac arrest
7. Cardiogenic shock, significant mitral regurgitation or intraventricular communication at inclusion
8. Mechanical ventilation at inclusion
9. Significant ventricular arrhythmia or atrioventricular block type II or III at inclusion
10. Decompensated chronic obstructive pulmonary disease at inclusion
11. chronic hepatocellular failure
12. MRI contraindications
13. Gadolinium chelates injection contraindications
14. Current treatment with morphine chlorhydrate, buprenorphine, nalbuphine, pentazocine