Eighty-six patients with heart attacks will be identified at our hospital. Post heart attack we will assess heart function, blood flow to the heart, and heart cell function. We will assess these parameters using nuclear cardiology scans that are used in everyday cardiology practice. The patients will then be divided into 2 groups. One group will receive a medication called G-CSF and the other group will receive a placebo. We will give this drug (1-2ml) for 4 days beneath the skin. We will take the patients blood during this time and measure how the drug affected their blood. The patients will all have the nuclear cardiology tests again in 6 weeks and 6 months to see how their heart is functioning. As well, they will have a six month angiogram. All the patients will otherwise receive optimal care from their Cardiologist. They will be seen at 6, 12, 24, and 52 weeks to assess them clinically.