According to one estimate, each year more than 900,000 people in the U.S. are diagnosed with heart failure, a progressive condition that occurs when the heart becomes damaged and is unable to adequately pump blood. There is no cure for the condition, and many patients die within five years of diagnosis.

The practice of using stem cells to regenerate failing hearts took a major step forward with the publication of a study that showed the treatment could cut the risk of cardiac events and even death in people with heart failure.

Because the heart does not regenerate cells on its own, heart failure has been treated with medications that can manage the condition, but not reverse its progression. Stem cell therapy utilizes special cells that have the ability to develop into many different cell types, including cardiac cells.

Researchers from the Texas Heart Institute in Houston enrolled 537 participants (average age 63, 20 percent female) with heart failure and reduced ejection fraction, which is a measure of the heart’s pumping efficiency.

The subjects were randomly divided into two groups: 261 adults received an injection of 150 million stem cells directly into the heart using a catheter; the remaining 276 adults received a placebo procedure. The study participants were discharged from the hospital the day after the procedure, and researchers followed them for an average of 30 months.

The study’s focus was to determine if stem cell therapy affected the likelihood of participants returning to the hospital for treatment of worsening heart failure. The researchers also tracked whether participants had a heart attack or stroke, or died, and evaluated levels of high-sensitivity C-reactive protein (hs-CRP), a marker in the blood indicating inflammation.

Although there was no decrease in hospitalization, there were several favorable findings:

• Those who received stem cell therapy had a 65 percent reduction in nonfatal heart attacks and strokes throughout the period of the study.

• Participants with high levels of inflammation were 79 percent less likely to have nonfatal heart attack or stroke after being treated with stem cells.

• Stem cell treatment reduced cardiac death by 80 percent in people with high levels of inflammation and less severe congestive heart failure.

Stem cell research on heart failure remains experimental, and is still being conducted in research settings.