In this study, patients who are within 72 hours of the onset of a heart attack and who are anemic (have a low red blood cell count) will be randomly assigned to one of two transfusion strategies while they are in the hospital: a liberal strategy of transfusing blood when the hematocrit falls below 30 percent (the current standard) or a conservative strategy of transfusing blood only when the hematocrit falls below 24 percent. It will then be determined which group fares better over the next 30 days.