Repairing the heart with stem cells

Could this experimental treatment reverse damage caused by a heart attack?

The heart muscle relies on a steady flow of oxygen-rich blood to nourish it and keep it pumping. During a heart attack, that blood flow is interrupted by a blockage in an artery. Without blood, the area of heart fed by the affected artery begins to die and scar tissue forms in the area. Over time, this damage can lead to heart failure, especially when one heart attack comes after another.

Though the heart is a tough organ, the damaged portions become unable to pump blood as efficiently as they once could. People who have had a heart attack therefore may face a lifetime of maintenance therapy—medications and other treatments aimed at preventing another heart attack and helping the heart work more efficiently.

A new treatment using stem cells—which have the potential to grow into a variety of heart cell types—could potentially repair and regenerate damaged heart tissue. In a study published last February in The Lancet, researchers treated 17 heart attack patients with an infusion of stem cells taken from their own hearts. A year after the procedure, the amount of scar tissue had shrunk by about 50%.

Research realities

These results sound dramatic, but are they an indication that we're getting close to perfecting this therapy? "This is a field where, depending on which investigator you ask, you can get incredibly different answers," says Dr. Richard Lee, professor of medicine at Harvard Medical School and a leading expert on stem cell therapy.

"The field is young. Some studies show only modest or no improvement in heart function, but others have shown dramatically improved function," he says. "We're waiting to see if other doctors can also achieve really good results in other patients."

Studies are producing such varied outcomes in part because researchers are taking different approaches to harvesting and using stem cells. Some stem cells are taken from the bone marrow of donors, others from the patient's own heart. It's not clear which approach is the most promising.

What are the risks?

Like any other therapy, injecting stem cells into the heart can fail or cause side effects. If the stem cells are taken from an unrelated donor, the body's immune system may reject them. And if the injected cells can't communicate with the heart's finely tuned electrical system, they may produce dangerous heart rhythms (arrhythmias). So far, side effects haven't been a major issue, though, and that has encouraged investigators to push onward.

"Most of the stem cell therapies for the heart have been surprisingly safe, but long-term effects are still a concern," says Dr. Lee. More long-term trials are needed to identify the role stem cell therapy will have in treating heart disease.

From theory to practice

When might stem cell therapy become a standard treatment for damaged heart muscle? "Some investigators think this is just a few years away," says Dr. Lee. "And then there are others who feel that there is much more work to be done."

As of now, stem cell therapy is available only to people who participate in a research trial. If you've had a heart attack or you have heart failure and you're interested in participating in a study of stem cell therapy, visit
www.clinicaltrials.gov and search for studies in your area (for example, search "stem cells," "heart," "Los Angeles"). When you participate in a study performed at a state-of-the-art heart center, even if you end up in the placebo arm of a study (meaning that you're getting an inactive therapy instead of a real treatment), you'll still ensure that you're getting first-rate care.