The purpose of this study is to investigate the effects of postconditioning on myocardial reperfusion in patients with ST-segment elevation myocardial infarction.

Inclusion Criteria General Inclusion Criteria

• Subject must be at least 18 years of age.

• Subject is able to verbally confirm understandings of risks, benefits and treatment alternatives of receiving postconditioning and he/she or his/her legally authorized representative provides written informed consent prior to any study related procedure

• Diagnosis of STEMI

  1. presence of chest pain for more than 30 minutes but less than 12 hours after symptom onset
  2. ST-segment elevation more than 1 mm in at least 2 contiguous leads

Angiographic Inclusion Criteria

• Target lesion(s) must be located in a native coronary artery
• Target lesion(s) must be amenable for percutaneous coronary intervention
• TIMI flow grade of infarct related arteries <2

General Exclusion Criteria

• Patients with hemodynamic instability or those with cardiogenic shock
• Target lesion is located in left main stem
• Rescue PCI after thrombolysis or facilitated PCI
• Non-cardiac co-morbid conditions are present with life expectancy <1 year or that may result in protocol non-compliance (per site investigator's medical judgment)
• Female of childbearing potential, unless a recent pregnancy test is negative, who possibly plan to become pregnant any time after enrollment into this study