Munkholm 1999.

Study characteristics
Methods	RCT with parallel design
Participants	22 adult participants with NYHA II or III heart failure 11 participants in the treatment group and 11 in the placebo group Adults (> 18 years) Before and after the treatment period, a right heart catheterisation was done
Interventions	Intervention: oral coenzyme Q10 100 mg twice daily for 12 weeks Control: placebo
Outcomes	Baseline and post‐therapeutic serum levels of coenzyme Q10 Left ventricular ejection fraction NYHA clinical status
Notes	This study is an invasive study investigating the treatment of congestive heart failure
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Randomised, no information about random sequence generation provided.
Allocation concealment (selection bias)	Unclear risk	No information given
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Double‐blind
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	No information given
Incomplete outcome data (attrition bias) All outcomes	Low risk	All participants completed the study
Selective reporting (reporting bias)	Unclear risk	No study protocol was available
Other bias	Low risk	No other risk of bias was found