This study will test the effects of G-CSF on the heart function of patients who have had a heart attack. It is a medication that that has been shown in an animal model to improve heart function after a heart attack. It is a medication that has been used for many years to treat patients with cancers and to increase the number of cells donated by healthy bone marrow donors. It has no serious side effects. It works by increasing the number of a person’s own stem cells in the blood. Stem cells are special cells that are present in our bodies that have the ability to form new cells. It had been thought that the heart could not make new cells after it has been damaged. Other investigators have shown that this might not be the case. It is now thought that after an injury, stem cells from the bone marrow can transform into cells of the injured tissue. Therefore, we are trying to increase the number of stem cells in the circulation with G-CSF so as to increase repair in the heart after it has been damaged. This strategy has never been tried in human beings and if successful could greatly reduce death and suffering from heart disease.