Dallas ? Heart attack patients who were treated with their own stem cells a few days after being hospitalized had significantly improved heart pumping ability, according to the largest, most rigorous clinical trial to date of the controversial therapy.

The improvement seen with stem cells was better than with the best drugs now available and it appears the therapy actually repaired damage done during heart attacks, said lead author Volker Schachinger, a cardiologist at J.W. Goethe University and the Third Medical Clinic of Cardiology in Frankfurt, Germany.

“It opens up a completely new way of treating heart disease,” Schachinger said. “So far, we only have medicine that can limit the damage. It’s better than the best drugs and it’s on top of the best drugs.”

Other cardiologists not associated with the study said although the findings are promising, more research involving a large number of patients needs to be done.

“We are taking small steps in defining stem cell therapy,” said Timothy Gardner, medical director of the Center for Heart and Vascular Health, in Wilmington, Del. “It’s (still) unclear what stem cells do when they get into the heart.”

The new study, which was presented Sunday at the American Heart Assn.’s annual scientific sessions, involved 204 heart attack patients who were treated at 16 centers in Germany and one in Switzerland.

Procedure

The patients underwent traditional angioplasty and stenting and, a few days later, they received either the stem cell treatment or a placebo.

The stem cells used in the study were not embryonic stem cells. They were so-called adult stem cells derived from bone marrow, which was extracted from the hips of the patients with a needle while they were under local anesthesia.

After filtering and a separation process done in a centrifuge, about 236 million progenitor bone marrow cells (about 50 milliliters) were isolated. The bone marrow cells contained cells that might become blood vessel or muscle cells.

After the cells were extracted, a catheter was threaded back up to the artery and a balloon was inflated to stop the flow of blood for about three minutes. During that time, the stem cells were injected into the artery. That was done three times.

‘Stiffer scar’

One theory is that the stem cells would be able to repair the part of the heart that was damaged during the heart attack, hopefully by regenerating heart muscle cells.

However, there is controversy over what the adult stem cells do. Some research in animals suggests that such cells do not become new heart muscle cells.

Gardner said it is possible that the cells merely are creating an environment that leads to a healthier form of scar tissue forming and that, in turn, provides some improvement in the heart’s pumping ability.

“It creates a stiffer scar,” he said.

He said the study seemed to show benefit, even if the reason wasn’t fully understood.

Philippe Menasche, a French cardiovascular surgeon who has done extensive research with adult stem cells, called the study a landmark paper.

“The data provide compelling evidence for a therapeutic benefit,” he said.

In addition to improved heart pumping ability, the patients seemed to have improved blood flow in their hearts, said Robert Bonow, chief of cardiology at Northwestern University’s Feinberg School of Medicine.

“That’s evidence that it’s not just forming healthy scar tissue,” said Bonow, who also is chief of cardiology at Northwestern Memorial Hospital.

Another possibility is that stem cells secrete proteins known as growth factors that make it easier for the heart to repair itself or that they may stimulate the creation of new blood vessels in the heart.

Significant improvement

Whatever the mechanism, the patients who received the stem cells had a significant improvement in the pumping ability of their heart, known as ejection fraction. After four months, the stem cell-treated patients had an average ejection fraction of 54, compared with 50 for the placebo group.

A healthy heart normally has an ejection fraction of 65 or more. In people with heart failure it generally is less than 40.

The improvement was the greatest in those who had the most severe heart attacks and in those who got their treatment more than five days after their heart attack.