FRIDAY, May 24 (HealthDay News) -- Regular doses of the dietary supplement Coenzyme Q10 cut in half the death rate of patients suffering from advanced heart failure, in a randomized double-blind trial.

Researchers also reported a significant decrease in the number of hospitalizations for heart failure patients being treated with Coenzyme Q10 (CoQ10). About 14 percent of patients taking the supplement suffered from a major cardiovascular event that required hospital treatment, compared with 25 percent of patients receiving placebos.

In heart failure, the heart becomes weak and can no longer pump enough oxygen- and nutrient-rich blood throughout the body. Patients often experience fatigue and breathing problems as the heart enlarges and pumps faster in an effort to meet the body's needs.

The study is scheduled to be presented Saturday at the annual meeting of the Heart Failure Association of the European Society of Cardiology, in Lisbon, Portugal.

"CoQ10 is the first medication to improve survival in chronic heart failure since ACE inhibitors and beta blockers more than a decade ago and should be added to standard heart failure therapy," lead researcher Svend Aage Mortensen, a professor with the Heart Center at Copenhagen University Hospital, in Denmark, said in a society news release.

While randomized clinical trails are considered the "gold standard" of studies, because this new study was presented at a medical meeting, the data and conclusions should be viewed as preliminary until published in a peer-reviewed journal.

American cardiologists greeted the reported findings with cautious optimism.

"This is a study that is very promising but requires replication in a second confirmatory trial," said Dr. Gregg Fonarow, a professor of cardiology at the University of California, Los Angeles, and a spokesman for the American Heart Association.

Fonarow noted that earlier, smaller trials with Coenzyme Q10 have produced mixed results. "Some studies have shown no effect, while other studies have shown some improvement, but not nearly the impressive effects displayed in this trial," he said.

Coenzyme Q10 occurs naturally in the body. It functions as an electron carrier in cellular mitochondria (the cell's "powerhouse") to help convert food to energy. It also is a powerful antioxidant, and has become a popular over-the-counter dietary supplement.

CoQ10 levels are decreased in the heart muscle of patients with heart failure, with the deficiency becoming more pronounced as the severity of their condition worsens, Mortensen said in the news release.

In this study, 420 patients with moderate to severe heart failure were tracked during two years. About half received 100 milligrams of CoQ10 three times a day, while the other half received a placebo.

By the end of the study, 18 patients from the CoQ10 group had died versus 36 deaths in the placebo group. Major adverse cardiovascular events requiring hospitalization had taken place in 29 CoQ10 patients, compared with 55 patients in the placebo group.

"It seems to be the largest trial so far to look at it in a rigorous way, to see if Coenzyme Q10 therapy affects outcomes in heart failure," said Dr. Margaret Redfield, head of the circulatory failure research group at Mayo Clinic. "As far as outcome trials go, it's still a pretty small trial. We have to interpret it cautiously. But it did seem to show a decrease in heart failure related events."

The potential of Coenzyme Q10 to treat heart failure patients has been a story told for more than two decades, added Dr. Michael Givertz, medical director for heart transplant and mechanical circulatory support at Brigham and Women's Hospital, Boston, and an associate professor of medicine for Harvard Medical School.

Studies have shown that Coenzyme Q10 does no harm and produces no side effects, Givertz said, but have not been able to definitively prove any solid benefit.

"The general recommendation to patients has been, probably not a huge benefit. It appears to be safe, it doesn't seem to have any side effects, it can't hurt, but it's pretty costly," he said. "Most cardiologists have not recommended it, and I don't think this size of a trial is going to change practice and change guidelines."

"I would say this is an intriguing trial," Givertz said. "It certainly deserves a definitive trial large enough to look at a mortality endpoint. I would look forward to seeing the full results published in a peer-reviewed journal."

More information

Visit the U.S. National Heart, Lung, and Blood Institute to learn more about heart failure.