The purpose of the study is to examine the effect of the cholesterol lowering agent Ezetimibe when used in addition to optimal treatment with Atorvastatin in patients with acute ST-Elevation Myocardial Infarction (STEMI) who have not been in prior statin therapy.

An area with arteriosclerosis not demanding intervention in a coronary vessel other than the infarct related is used as measuring point and is examined at time of the infarction and after 12 month using intravascular ultrasound and optical coherence tomography. At the same time the same techniques are used to examine the implanted stent.

Optical coherence tomography (OCT) and intravascular ultrasound (IVUS) with tissue characterization (IVUS-TC) are relatively new expansions to intravascular assessments, and has the capacity to assess plaque composition and, potentially, to identify vulnerable plaques. One of the mechanisms by which statins improve patient outcomes may be by changing the composition of a "vulnerable" plaque. The main effect is believed to rely on a lowering of LDL-c. The question is whether a further reduction of LDL by adding ezetimibe to optimal cholesterol lowering therapy using statins may result in further plaque stabilization or reduction. This is the hypothesis of the current study.

100 patients are randomized to Ezetimibe 10 mg per day or placebo. All patients are treated with Atorvastatin 80 mg. OCT and IVUS are performed at inclusion (typically the day after Primary PCI) and again at follow-up after 12 month.

Inclusion Criteria:

• ST segment elevation acute myocardial infarction
• 20% < angiographic diameter stenosis < 50% on a not previously revascularized native coronary artery
• Statin naïve
• In fertile women: Ongoing contraception with IUD or hormonal contraception.

Exclusion Criteria:

• Pharmacologic lipid lowering treatment before index hospitalization
• Atrial fibrillation, not well rate-controlled
• Ventricle frequency variation with more than a factor 2 over 1 minute
• Unconscious patients
• History of statin induced myopathy, or serious hypersensitivity reaction to other HMG-CoA reductase inhibitors (statins) including Atorvastatin.
• Pregnant women, women who are breast feeding, and women of childbearing potential who are not using chemical or mechanical contraception or have a positive serum pregnancy test (a serum-human chorionic gonadotrophin [Beta-HCG] analysis)
• History of malignancy (unless a documented disease free period exceeding 5-years is present) with the exception of basal cell or squamous cell carcinoma of the skin. Women with a history of cervical dysplasia would be permitted to enter the study provided they had 3 consecutive clear Papanicolaou (Pap) smears
• Uncontrolled hypothyroidism (TSH > 1.5xULN)
• Abnormal LFT's
• History of alcohol or drug abuse within the last 5 years (this may affect compliance)
• Current active liver disease (ALT/SGPT >2xULN or severe hepatic impairment (to protect patient safety as directed on the labels of currently approved statins)
• Unexplained creatine kinase (CK > 3xULN) (To protect patient safety) (will be increased at baseline because of acute ST segment elevation myocardial infarction a few days before enrolment)
• Serum creatinine >176mmol/L (2.0mg/dL) (unless the protocol specifically aims to investigate a chronic renal disease population)
• Participation in another investigational drug study less than 4 weeks before enrolment in the study, or according to subjects local ethics committee requirements where a larger period is stipulated (to avoid potential misinterpretation of overlapping adverse events)
• Treatments with cyclosporine
• Treatment with gemfibrozil