Objective: This study was a pilot trial to determine safety and feasibility of intracoronary infusion of mononuclear bone marrow cells (MBMC) in patients with acute myocardial infarction (MI). Background: Studies reporting the effect of MBMC therapy on improvement of left ventricular (LV) function have shown variable results. The HEBE trial is a large multi-center, randomized trial that currently enrolls patients. Prior to this trial we performed a pilot study. Methods: Twenty-six patients with a first acute MI were prospectively enrolled in eight centers. Bone marrow aspiration was performed at a median of 6 days after primary PCI (interquartile range, 5-7 days). MBMC were isolated by gradient centrifugation and were infused intracoronary the same day. All patients underwent magnetic resonance imaging before cell infusion and after 4 months. Clinical events were assessed up to 12 months. Results: Within 10 hr after bone marrow aspiration, 246 +/- 133 X 10(6) MBMC were infused, of which 3.9 +/- 2.3 x 10(6) cells were CD34(+). In one patient, this procedure was complicated by local dissection. LV ejection fraction significantly increased from 45.0 +/- 6.3% to 47.2 +/- 6.5% (P = 0.03). Systolic wall thickening in dysfunctional segments at baseline improved with 0.9 +/- 0.7 mm (P < 0.001). Infarct size decreased 37% from 17.8 +/- 8.2 to 11.2 +/- 4.2 gram (P < 0.001). During 12-month follow-up, 3 additional revascularizations were performed and an ICD was implanted in one patient, 3 weeks after PCI. Conclusion: In patients with acute MI, intracoronary infusion of MBMC is safe in a multi-center setting. At 4-month follow-up, a modest increase in global and regional LV function was observed, with a concomitant decrease in infarct size. (c) 2008Wiley-Liss,Inc.