Coenzyme Q10 for heart failure.

BACKGROUND

Coenzyme Q10, or ubiquinone, is a non-prescription nutritional supplement. It is a fat-soluble molecule that acts as an electron carrier in mitochondria and as a coenzyme for mitochondrial enzymes. Coenzyme Q10 deficiency may be associated with a multitude of diseases including heart failure. The severity of heart failure correlates with the severity of coenzyme Q10 deficiency. Emerging data suggest that the harmful effects of reactive oxygen species are increased in patients with heart failure and coenzyme Q10 may help to reduce these toxic effects because of its antioxidant activity. Coenzyme Q10 may also have a role in stabilising myocardial calcium-dependent ion channels and preventing the consumption of metabolites essential for adenosine-5'-triphosphate (ATP) synthesis. Coenzyme Q10, although not a primary recommended treatment, could be beneficial to patients with heart failure. Several randomised controlled trials have compared coenzyme Q10 to other therapeutic modalities, but no systematic review of existing randomised trials has been conducted.

OBJECTIVES

To review the safety and efficacy of coenzyme Q10 in heart failure.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (2012, Issue 12); MEDLINE OVID (1950 to January Week 3 2013) and EMBASE OVID (1980 to 2013 Week 03) on 24 January 2013; Web of Science with Conference Proceedings (1970 to January 2013) and CINAHL Plus (1981 to January 2013) on 25 January 2013; and AMED (Allied and Complementary Medicine) (1985 to January 2013) on 28 January 2013. We applied no language restrictions.

SELECTION CRITERIA

We included randomised controlled trials of either parallel or cross-over design that assessed the beneficial and harmful effects of coenzyme Q10 in patients with heart failure. When cross-over studies were identified, we considered data only from the first phase.

DATA COLLECTION AND ANALYSIS

Two authors independently extracted data from the included studies onto a pre-designed data extraction form. We then entered the data into Review Manager 5.2 for analysis. We assessed study risk of bias using the Cochrane 'Risk of bias' tool. For dichotomous data, we calculated the risk ratio and for continuous data the mean difference (MD). Where appropriate data were available, we performed meta-analysis. For this review we prioritised data from pooled analyses only. Where meta-analysis was not possible, we wrote a narrative synthesis. We provided a QUOROM flow chart to show the flow of papers.

MAIN RESULTS

We included seven studies with 914 participants comparing conenzyme Q10 versus placebo. There were no data on clinical events from published randomised trials. The included studies had small sample sizes. Meta-analysis was only possible for a few physiological measures and there was substantial heterogeneity.Only one study reported on total mortality, major cardiovascular events and hospitalisation. Five trials reported on the New York Heart Association (NYHA) classification of clinical status, but it was impossible to pool data due to heterogeneity. None of the included trials considered quality of life, exercise variables, adverse events or cost-effectiveness as outcome measures. Pooled analysis suggests that the use of coenzyme Q10 has no clear effect on left ventricular ejection fraction (MD -2.26; 95% confidence interval (CI) -15.49 to 10.97, n = 60) or exercise capacity (MD 12.79; 95% CI -140.12 to 165.70, n = 85). Pooled data did indicate that supplementation increased blood levels of coenzyme Q10 (MD 1.46; 95% CI 1.19 to 1.72, n = 112). However, there are only a small number of small studies with a risk of bias, so these results should be interpreted with caution.

AUTHORS' CONCLUSIONS: No conclusions can be drawn on the benefits or harms of coenzyme Q10 in heart failure at this time as trials published to date lack information on clinically relevant endpoints. Furthermore, the existing data are derived from small, heterogeneous trials that concentrate on physiological measures: their results are inconclusive. Until further evidence emerges to support the use of coenzyme Q10 in heart failure, there might be a need to re-evaluate whether further trials testing coenzyme Q10 in heart failure are desirable.