July 27 (Bloomberg) -- Women with heart failure may not always be getting the best treatment because they’re less likely to enroll in clinical trials that assess the most effective therapies for them, an analysis of previous studies found.

The research suggested that some pacemakers and certain medicines, known as beta blockers and aldosterone antagonists, may help women, according to research in the Aug. 4 issue of the Journal of the American College of Cardiology. There isn’t enough evidence to show whether some other common treatments, including implantable defibrillators, work for women as well as for men, the authors said.

Heart failure, a condition in which the heart can’t pump enough blood throughout the body, affects about 5 million Americans, and about half are women, the article said. Doctors treat men and women similarly, lead author Eileen Hsich said. A better understanding of heart failure in women may help doctors provide the best care, she said.

“Our review raises some concern that some treatments may be more effective and some less effective,” said Hsich, director of the Women’s Heart Failure Clinic at the Cleveland Clinic in Ohio, in a July 24 telephone interview. “Female patients need to know that these drugs were tested mostly in men. In order to change our future so that the No. 1 cause of death isn’t cardiovascular disease, we need to have more women enrolled in studies.”

Nine Studies

The researchers analyzed every major study that has guided heart failure practice, Hsich said.

The review found that nine heart failure studies in the past decade, on average, included about 28 percent women. Only one, the African-American Heart Failure Trial, achieved about 40 percent women, Hsich said.

The analysis found that heart failure affects women at an older age than men. Women also tend to have heart failure when their hearts are strong but the organ can’t relax and fill properly, causing fluid to back up into other parts of the body, she said.

The research analysis showed that drugs called beta blockers, found in previous studies to help when added to angiotensin-converting enzyme inhibitors, reduced hospital stays for women and men. Some of the studies also showed an improvement in survival for women given this treatment.

One medical trial found the heart medicine carvedilol improved survival in women with moderate symptoms, similar to the benefits seen for men. Carvedilol is available as a generic and is sold as Coreg by GlaxoSmithKline Plc.

Fewer Deaths

Another drug group called aldosterone antagonists was shown in two studies to reduce deaths for women as well as men, according to the analysis. Aldosterone antagonists include spironolactone, available as a generic and as Aldactone by Pfizer Inc., and eplerenone, available as a generic and as Inspra by Pfizer.

The analysis didn’t find as clear a benefit for women taking drugs called ACE, or angiotensin-converting enzyme, inhibitors, or for women who have implantable defibrillators. That may be because too few women were enrolled in studies of their effectiveness, Hsich said.

Women tend to get heart failure because they have high blood pressure or a disease of their heart valves, while in men coronary artery disease is an underlying cause more often, according to the journal article.

Gender Reporting

In 1993, a federal law was passed requiring that a sufficient number of women be included in clinical trials sponsored by the U.S. National Institutes of Health to ensure meaningful results based on gender could be reported. Still, the authors said, there are a small number of heart studies reporting gender-specific data. Hsich said many more men than women are willing to participate in heart-failure studies.

“Once they’re diagnosed with any cardiovascular disease, then women need to start requesting being part of research,” she said.

The analysis was requested by the editors of the Journal of the American College of Cardiology, said Hsich. She also reported grant support from the American Heart Association.

To contact the reporter on this story: Nicole Ostrow in New York at nostrow1@bloomberg.net.

Last Updated: July 27, 2009 17:00 EDT