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Coenzyme Q10 for heart failure. (Alternative Medicine).

* Coenzyme Q10 depletion has been postulated as a contributory factor in myocardial destruction.

* Recent clinical trials have failed to confirm the benefits of coenzyme Q10 seen in early studies.

Rationale for Use

First identified by researchers at the University of Wisconsin in 1957, coenzyme Q10 is a naturally occurring compound essential to mitochondrial oxidative phosphorylation. It also acts as an antioxidant scavenger and exhibits membrane-stabilizing properties.

In healthy persons, it is found in high concentrations in the mitochondria of heart, kidney, and liver cells. Coenzyme Q10 is depleted in myocardial biopsies of patients with congestive heart failure. Accordingly, some investigators have postulated that supplementation with coenzyme Q10 could help prevent myocardial destruction, making the supplement a potentially beneficial treatment option.

Clinical Studies

Early Japanese studies suggested efficacy, and in 1974 coenzyme Q10 was licensed in Japan for the treatment of heart failure. Subsequent U.S. and European studies have shown contradictory results.

In one Italian study of 641 patients with New York Heart Association class III or IV heart failure, hospitalization for serious complications was compared among patients randomized to receive 50 mg of coenzyme Q10 two to three times per day, or placebo, plus their standard medications (Chin. Investig. 71[8, suppl.]:S134-36, 1993). The double-blind trial lasted for 1 year and enrolled patients from 33 centers.

During the study, 16 patients in the coenzyme Q10 group died, as did 21 in the placebo group; this difference was not significant.

But statistically significant improvements in functional status were observed in the active treatment group at 3, 6, and 12 months; no changes were noted in the placebo group. The incidence of acute pulmonary edema and arrhythmias was significantly lower in the coenzyme Q10 group, and about 40% of the placebo group and 20% of the active treatment group required hospitalization.

The authors extrapolated that treating 1,000 patients with coenzyme Q10 for 1 year would prevent 200 hospitalizations.

Two recent U.S. studies, however, found no benefit for coenzyme Q10. In a double-blind crossover study, 30 patients with chronic heart failure averaging 41 months in duration were randomized to 33 mg of coenzyme Q10 three times per day or placebo (J. Am. Coll. Cardiol. 33[6]:1549-52, 1999). All patients were clinically stable on maximum tolerated doses of angiotensin-converting enzyme inhibitors and other agents, including digoxin and nitrates.

An initial 12-week treatment phase was followed by a 1-week washout period, after which patients were switched to the alternate treatment arm. Transthoracic echocardiography was performed at the end of each phase; right heart catheterization was done at baseline and at the end of each treatment phase to determine capillary wedge pressure and cardiac output. Left ventricular volume assessment and ejection fraction also were calculated.

"No demonstrable improvement" was seen with coenzyme Q-10 treatment in resting left ventricular ejection fraction, volumes, or pulmonary wedge pressure, the authors noted.

"The pathophysiology of heart failure may be too complex to be explained simply by the depletion of myocardial energy stores and therefore likely to be reversed by coenzyme Q[10]," the investigators wrote.

Another randomized study that included 55 patients with class III and IV heart failure evaluated the effects of coenzyme Q10 treatment on peak oxygen consumption, ejection fraction, and exercise duration (Ann. Intern. Med. 132[8]:636-40, 2000).

At the study's outset, all patients had ejection fractions below 40%, as evaluated by radionuclide ventriculography. Maximal oxygen consumption was less than 17 mL/kg of body weight per minute.

Patients were given 200 mg of coenzyme Q10 or placebo daily for 6 months. All were being treated with ACE inhibitors and digoxin; many also were receiving [beta]-blockers and diuretics.

At the conclusion of the study, there were no significant differences in maximal oxygen consumption or left ventricular ejection fraction with coenzyme Q10 treatment, the researchers reported. One patient in each group had symptomatic improvement, and about three-fourths said they felt neither better nor worse than they did before the treatment.

The investigators noted that in earlier trials ejection fractions were determined echocardiographically rather than with radionuclide ventriculography. And of the Italian trial in which fewer hospitalizations were seen with coenzyme Q10 treatment, they wrote, "this study also reported high rates of pulmonary edema and cardiac asthma in these patients and used vague definitions."

They concluded that patients seeking alternative or complementary treatments "should be made aware that coenzyme Q10 has been studied in randomized, blinded, and controlled studies and that these studies have found no detectable benefit."

Clinical Concerns

Despite initial studies that suggested promise for coenzyme Q10, benefits have not been seen in stage III and IV heart failure. Whether it will be useful in stage I or II heart failure, before myocardial stores are depleted, is not known.

"It may be that you have to replenish it early in the disease course to have any effect," said Dr. Philippe Szapary, of the University of Pennsylvania, Philadelphia.

"I don't recommend it for my patients with stage III or IV heart failure," he said, citing the availability of agents with proven efficacy: ACE inhibitors and [beta]-blockers.

Coenzyme Q10 can cost about $60-$80 per month retail. There also is a potential for an interaction with war-farin, commonly used in patients with heart failure.
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Author:Walsh, Nancy
Publication:Internal Medicine News
Geographic Code:1USA
Date:Jun 1, 2002
Words:873
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