“If I had chronic heart failure, I certainly would consider (using) it,” said review co-author Dr. Max Pittler, deputy director of complementary medicine at Peninsula Medical School in Exeter, England.

The review does not include results of a large new study — unpublished to date — that suggested hawthorn has only a limited affect on lifespan.

At issue is heart failure, a common condition that is both debilitating and deadly. An estimated five million Americans suffer from heart failure, which is often the result of clogged arteries that put stress on the heart by forcing it to work harder.

As a result, the heart becomes larger while failing to effectively move blood around the body. This causes fluids to build up in the legs and lungs, often causing shortness of breath and other symptoms.

Perhaps the most famous heart failure patient is Vice President Dick Cheney, who has suffered from a long history of cardiac problems and has a defibrillator implanted in his chest.

According to the new review, the hawthorn bush produces one of the most commonly used herbal medicines in the United States. Many believe that hawthorn extract improves heart health, lowers cholesterol and boosts antioxidant levels.

To determine whether hawthorn is actually an effective treatment, Pittler and colleagues searched the medical literature for high-quality studies into the use of the herb in chronic heart failure patients.

The review of the studies appears in the latest issue of The Cochrane Library, a publication of The Cochrane Collaboration, an international organization that evaluates medical research. Systematic reviews like this one draw evidence-based conclusions about medical practice after considering both the content and quality of existing medical trials on a topic.

The researchers found 14 studies that met their criteria, several of which looked at the use of hawthorn as an addition to conventional medications.

The review authors combined the results of 10 studies of 855 patients into a meta-analysis. Compared to placebo, hawthorn extract boosted the maximum level of physiological workload — a fact that the review authors described as significant, although they acknowledged they based the finding on small numbers of studies and patients.

The analysis found that hawthorn, as compared to placebo, also decreased the “pressure-heart rate product,” a measurement of how much oxygen is used by the heart. In addition, the analysis reports that two other measurements — exercise tolerance, and shortness of breath and fatigue — improved “significantly” in patients who used hawthorn.

Side effects were reported to be “infrequent, mild and transient,” and included nausea, dizziness and heart and gastrointestinal complaints. The studies reviewed did not examine death rates in detail, however.

Overall, the review showed a “significant benefit in symptom control and physiologic outcomes” in patients who took hawthorn, Pittler said. According to him, the extract appears to boost the strength of heart contractions, increase blood flow through arteries and reduce irregular heartbeats.

There are some caveats, however. Only seven of the 14 trials specified that patients were taking conventional drugs. In addition, patients included in the studies had mild-to-moderate heart failure. Pittler said hawthorn might cause greater side effects in patients who must take drugs that are more powerful to control their disease.

Dr. Gregg Fonarow, director of the Heart Failure Program at the University of California at Los Angeles, said the larger hawthorn study whose results were released last year impressed him more. The study, which was not included in the review because it thus far remains unpublished, found only limited benefit.

“It does indeed demonstrate that [hawthorn] is not a harmful therapy, but it’s one that is not particularly helpful nor that would be recommended,” Fonarow said. “It’s naturally attractive to think there is something over the counter or naturally occurring that may help improve outcome. Unfortunately, we’ve not been able to identify that so far.”

The Cochrane Collaboration is an international nonprofit, independent organization that produces and disseminates systematic reviews of health care interventions and promotes the search for evidence in the form of clinical trials and other studies of interventions. Visit http://www.cochrane.org for more information.

Pittler MH, Guo R, Ernst E. Hawthorn extract for treating chronic heart failure. Cochrane Database of Systematic Reviews 2008, Issue 1.