The majority of evidence available indicates that patients with heart failure may benefit from using CoEnzyme Q₁₀. Six studies reported a benefit of using CoQ₁₀. Five of these were of neutral quality and four contained small sample sizes. A larger systematic review, which included five placebo controlled, randomized design studies along with a meta-analysis, found four studies with positive outcomes with supplementation of CoQ₁₀ in patients with HF. Outcomes from three of these four studies included a statistically significant increase in exercise tolerance and quality of life with a decrease in symptomolgy. One study (with a small sample size; n=46) found no benefit from CoQ₁₀ in patients with heart failure. 

• Grade I means there is Good/Strong evidence supporting the statement;
• Grade II is Fair;
• Grade III is Limited/Weak;
• Grade IV is Expert Opinion Only;
• Grade V is Not Assignable.
• High (A) means we are very confident that the true effect lies close to that of the estimate of the effect;
• Moderate (B) means we are moderately confident in the effect estimate;
• Low (C) means our confidence in the effect estimate is limited;
• Very Low (D) means we have very little confidence in the effect estimate.
• Ungraded means a grade is not assignable.