SAN FRANCISCO -- Stem cells grown from patients' own cardiac tissue can heal damage once thought to be permanent after a heart attack, according to a study that suggests the experimental approach may one day help stave off heart failure.

In a trial of 25 heart-attack patients, 17 who got the stem cell treatment showed a 50 percent reduction in cardiac scar tissue compared with no improvement for the eight who received standard care. The results were published Tuesday in the medical journal Lancet.

The study, by researchers from Cedars-Sinai Heart Institute in Los Angeles and Johns Hopkins University in Baltimore, tested the approach in patients who recently suffered a heart attack, with the goal that repairing the damage might help stave off failure. While patients getting the stem cells showed no more improvement in heart function than those who didn't get the experimental therapy, the theory is that new tissue regenerated by the stem cells can strengthen the heart, said Eduardo Marban, the study's lead author and director of Cedars-Sinai Heart Institute.

The stem cells were implanted within five weeks after patients suffering heart attacks. Doctors removed heart tissue, about the size of half a raisin, using a minimally invasive procedure that involved a thin needle threaded through the veins. After cultivating the stem cells from the tissue, doctors reinserted 12.5 million to 25 million cells using a second minimally invasive procedure.

A year after the procedure, six patients in the stem cell group had serious side effects.

While the main goal of the trial was to examine safety, the decrease in scar tissue in those treated merits a larger study that focuses on broader clinical outcomes, researchers said.

"If we can regenerate the whole heart, then the patient would be completely normal," Dr. Marban said. "We haven't fulfilled that yet, but we've gotten rid of half of the injury, and that's a good start."

First published on February 15, 2012 at 12:00 am

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Heart's stem cells used to mend attack damage