A stem cell treatment for patients experiencing heart failure significantly improved their heart function in a small but promising new study. In heart failure, the heart loses its ability to efficiently pump blood.

It is most often caused by a heart attack, which destroys some of the muscle tissue essential to a normal heartbeat.

In this new study, patients were injected with adult stem cells taken from their own hearts. These are a special kind of undifferentiated cell found throughout the body that helps to maintain and repair the tissue in which they are found.

Doctors use a measure called 'ejection fraction' to describe the heart's ability to pump blood. Study author Dr. Roberto Bolli of the University of Louisville says people in the control group showed no significant improvement in that measure.

But he called the improvement in the stem cell patients "striking." At four months, the pumping ability of the heart was markedly improved. The ejection fraction increased by eight points at four months, and at one year it increased by 12 points.

Now, this is a huge increase, much greater than what we even hoped for when we started our study. And Bolli says there was a significant improvement in the ability of the stem cell recipients to exercise.

The study participants also got MRI scans before and after treatment. A year after getting the stem cells, the images showed a 30 percent reduction in the scars of dead heart muscle.

The reduction of the scar implies that new heart muscle is being produced to replace that scar. And so it is evidence that the stem cells are regenerating new heart muscle.

This ongoing study is very small, with just 16 patients in the stem cells group, plus seven more in the control group. But a commentary published with his paper says Bolli's findings "raise new optimism" because of the study's rigorous quality and unexpectedly good results.

Bolli published his findings in The Lancet and presented them at the American Heart Association meeting in Florida.

Also at that Heart Association meeting: another report of stem cell research, though with less promising results.

In a study published in the journal of the American Medical Association, JAMA, researchers gave recent heart attack victims stem cells taken from their bone marrow.

The idea was to prevent the onset of heart failure. Earlier studies had suggested the technique might work.

But in this case, after six months there was no improvement in heart function. That's today's health brief. This is Paul Chan reporting.