Preclinical studies suggest that administration of cytokines to mobilize stem cells and alter the postinfarction inflammatory cardiac milieu may enhance left ventricular function and survival.

Eighteen patients were randomized in a 2:1 double-blind fashion to granulocyte colony stimulating factor (G-CSF) (at 5 escalating to 10 μg/kg per day subcutaneously for 5 days [6 patients in each group]) or matching placebo. Principal safety and efficacy end points were rupture-free survival and recovery of left ventricular function, respectively. Mobilization into the systemic circulation of precursor CD34⁺ and CD117⁺ stem cells at 30 days were also assessed.

Baseline characteristics of the 3 groups were well matched. Mean ± SD creatine kinase–MB maximum was 349 (169) IU. Follow-up averaged 30 ± 6, 21 ± 11, and 11 ± 6 months in the 3 groups, respectively. Precursor cell mobilization increased by a factor of 5 to 7 in the G-CSF–treated patients. There were no deaths or myocardial ruptures leading to tamponade through 30 days. Baseline and 30-day left ventricular ejection fraction in the placebo, 5-μg, and 10-μg dose groups were 33.7% (1.6) and 41.7% (8.2), 36.8% (7.5) and 41.3% (10.3), and 33.5% (4.8) and 38.7% (7.3), respectively (P = NS for all between-group comparisons). No differences between the G-CSF and placebo groups were noted in any other measure of left ventricular systolic or diastolic function 30 days after infarction.

Despite demonstrated mobilization of precursor stem cells in a timely fashion, in this small, pilot-scale randomized trial involving patients with large myocardial infarction, we were unable to demonstrate improvement in left ventricular function at 30 days.