Mareev 2017.

Study characteristics
Methods	double‐blinded, randomised controlled clinical trial with parallel design
Participants	148 participants with heart failure NYHA functional class I to IV and LVEF < 45% who were on optimal medical therapy. Randomisation ratio was 2:1 101 participants in the coenzyme Q10 group and 47 participants in the placebo group
Interventions	Intervention with dose: coenzyme Q10 nasal drops (90 mg/day = equivalent 225 mg/day for liposoluble tablets) Control: placebo
Outcomes	All outcomes measured at 24 weeks dynamics of NYHA functional class, The Minnesota Living with Heart Failure Questionnaire, the Kansas City Cardiomyopathy Questionnaire, distance of 6‐minute walking test, LVEF, brain natriuretic peptide level, coenzyme Q10 levels, adverse events
Notes	300 participants were initially included in the study, 152 of them failed to follow up and were excluded from the analysis.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Random sequence generation method was not mentioned
Allocation concealment (selection bias)	Unclear risk	Details about allocation concealment were not mentioned
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Double‐blinded
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	No information about blinding the assessors given
Incomplete outcome data (attrition bias) All outcomes	High risk	Of 300 enrolled participants, 152 participants were excluded as they failed to follow up; only 148 participants were included in the analysis
Selective reporting (reporting bias)	Unclear risk	No study protocol was available
Other bias	Low risk	No other bias could be found