To treat patients with acute myocardial infarction, primary percutaneous coronary intervention (PCI) will be performed with the use of an everolimus-eluting cobalt- chromium stent (everolimus-eluting stent: EES, Xience Prime, Xpedition), which is the current standard drug-eluting stent (DES). Vascular responses at the site of stent placement will be evaluated by optical coherence tomography (OCT) at 2 weeks or 3 months and at 12 months after stent placement, along with observation of changes over time in the target vessel. The relationships between OCT findings and the time course of platelet aggregation and between OCT findings and the occurrence of major cardio- cerebrovascular events will also be elucidated.

Inclusion Criteria:

- AMI definition is accordance with the third universal definition of ESC /ACCF/ AHA/ WHF Task Force10, detection of a rise and/or fall of cardiac biomarker values [preferably cardiac troponin (cTn) I or T] with at least one value above the 99th percentile upper reference limit (URL) and with at least one of the following: Symptoms of ischemia. New or presumed new significant ST-segment-T wave (ST-T) changes or new left bundlebranch block (LBBB).

Development of pathological Q waves in the ECG. Imaging evidence of new loss of viable myocardium or new regional wall motion abnormality.

Identification of an intracoronary thrombus by angiography or autopsy Of the AMI patients who met the above definition, the criterial for inclusion is limited to STEMI patients. STEMI is defined as new ST elevation at the J point in at least 2 contiguous leads of equal or greater than2 mm (0.2 mV) in men equal or greater than1.5 mm (0.15 mV) in women in leads V2-V3 and/or of equal or greater than 1 mm (0.1 mV) in other contiguous chest leads or the limb leads

• Patients having at least one de novo lesion in a coronary artery in whom PCI with a DES is indicated.
• Patients aged 20 to less than 85 years at the time of informed consent
• Patients who have provided informed consent written by themselves
• Patients who are able to undergo OCT examinations of the site of stent placement at 2 weeks or 3 months and at 12 months.

Exclusion Criteria:

• Shock
• Patients who are judged incapable of undergoing clinical follow-up 12 months after PCI (Consider also the location of patients' residences)
• Lack of specific findings of ACS by angiography (Left to the operator's decision.)
• The culprit lesion is the left main coronary trunk
• Lesion with the reference vascular diameter less than 2.0mm or not less than 4.5mm by visual evaluation.
• Chronic renal failure with serum creatinine level not less than 2.0mg/dl on hospital visit
• Patients on hemodialysis Cancer patients whose vital prognosis is expected to be within 2 years. Surgery that requires discontinuation of the antiplatelet agent is scheduled within 3 months
• Patients who experienced adverse reaction to aspirin or clopidogrel (this shall not apply for patients in whom safety of ticlopidine is confirmed)
• Patients who took warfarin before the onset
• Patients under 20 years old
• Pregnant women
• AMI due to stent thrombosis at prior stented segment.

primary care clinic