During a heart attack , part of the heart muscle is damaged or dies when its oxygen supply is cut off by a blood clot in one of the coronary arteries. Immediate treatment involves medications to help dissolve the clot and/or the insertion of a balloon followed by a stent to remove the clot and hold the artery open. While these treatments can reduce the extent of damage to the heart muscle, they cannot restore any tissue already damaged. Too much damaged tissue worsens the heart’s pumping ability, leading to heart failure, which is a major cause of disability and death following a heart attack. To assess the risk of heart failure, doctors often evaluate function of the left ventricle (LV, the main pumping chamber). They do this by calculating the left ventricular ejection fraction (LVEF), a measure of how well the heart is pumping.

Cells from a patient’s bone marrow, called progenitor cells, may improve function of the ventricle. Progenitor cells are immature and can develop into various types of cells. At first researchers thought that once inside the heart, progenitor cells would develop into cardiac cells to replace those that had died. But newer research indicates that it may be by some other means that progenitor cells appear to improve heart function.

Several research teams are examining the use of progenitor cells in heart attack patients. The largest trial to date is by a group of German researchers who reported that patients who received progenitor cells shortly after a heart attack showed significantly greater improvements in left ventricle function than those given a placebo. These findings, and those from two other trials on this topic, are published in the September 21, 2006 New England Journal of Medicine .

About the Study

German researchers recruited 204 patients, ages 18-80, who suffered a heart attack that damaged the left ventricle. Within six days after initial treatment, a sample of each person’s bone marrow was removed and progenitor cells were isolated. Then, patients were randomly assigned to receive an infusion of either their own bone marrow (progenitor) cells (BMC) or a placebo into the damaged section of the heart. An angiogram was done immediately after the infusion and again four months later to determine the left ventricular ejection fraction. The researchers compared the changes in LVEF over four months in the BMC and placebo groups.

After four months, patients who received a BMC infusion showed significantly greater improvements in LVEF than those who received a placebo. This finding remained significant after adjusting for diabetes and other potential conditions that could affect LVEF. The most improvement was seen among patients with the worst LVEFs, and therefore the most damage, at baseline. At the one-year follow-up, significantly fewer adverse events occurred in the BMC group than in the placebo group.

A limitation of this study was its inability to determine if the demonstrated LVEF improvements would lead to improvements in quality of life or reductions in deaths associated with heart failure and other heart attack complications.

How Does This Affect You?

Given the apparent benefits of BMC infusion compared to placebo, are progenitor cells a breakthrough in the prevention of heart failure following a heart attack? It’s too soon to say, as the five most recent trials on the topic have reported mixed results—two positive, two negative, and one positive at six months but negative at 18 months.

The New England Journal of Medicine also published a study, led by Dr. Birgit Assmus, which found a “modest” but significant improvement in LVEF following a BMC infusion among patients who had a heart attack at least three months earlier. Another trial, led by Dr. Ketil Lunde, in the same journal issue found no improvement in LVEF and no difference in adverse events six months after BMC infusion. This study used multiple imaging techniques to determine LVEF.

Progenitor cell therapy is not ready for routine practice. Further refinements are needed to make BMC infusions more effective and additional research is needed to determine exactly which heart attack victims are likely to benefit most. Although BMC infusions may one day become common practice, they are unlikely to replace currently available treatments that have already greatly improved the prognosis of patients with heart failure.