Autologous stem cells may improve myocardial regeneration after intracoronary administration in patients with acute myocardial infarction. The primary hypothesis of this prospective, placebo-controlled, double-blind trial is that the increase of ejection fraction determined by magnetic resonance imaging between baseline and 6 months follow-up is superior in active treated patients compared to patients receiving placebo. The study includes an integrated pilot phase of 40 patients for evaluation of left ventricular ejection fraction determined by cardiac magnetic resonance imaging. Based on the data of this analysis the final sample size will be calculated. The primary endpoint is the improvement in left ventricular ejection fraction with an assumed 2.5% higher improvement in the cell treated population compared to the placebo treated group.

There is a 2:1 randomization for bone marrow cell therapy versus placebo therapy. Patients will be stratified according to age, localization of myocardial infarction and left ventricular function.

Inclusion Criteria:

• acute myocardial infarction with time to revascularization >6 hours from symptom start
• clear target vessel
• large myocardial infarction defined as: proximal vessel occlusion, CK > 1000 U/L, myocardial scar in magnetic resonance imaging > 10% of left ventricular muscle mass
• potential prior thrombolysis
• written informed consent

Exclusion Criteria:

• acute myocardial infarction with revascularization within 6 hours after symptom start
• prior myocardial infarction
• no clear target vessel
• contraindication for magnetic resonance imaging (e.g. pacemaker, ICD)
• severely depressed left ventricular ejection fraction (less than 20% in magnetic resonance imaging)
• prior hematologic disease
• prior chemo therapy
• prior stem cell transplantation
• prior treatment with G-CSF
• known alteration of the bone marrow by alcohol or drugs, e.g. agranulocytosis
• local infection of puncture sites