Lewis 2007.

Methods	Randomised, parallel‐group, double‐blinded, single‐centre, placebo‐controlled trial 12 weeks duration
Participants	Inclusion criteria: adults who were 18 years of age LVSD (LVEF > 0.4) NYHA class II to IV chronic HF despite standard HF therapies with secondary PH as defined by a mean PAP of 25 mmHg (WHO Group 2) Participants who enrolled in a previous study of the short‐term effects of 1‐time administration of sildenafil on exercise capacity were eligible to enrol in this study Exclusion criteria: Those with a noncardiac limitation to exercise Provocable ischaemia Haemodynamic instability Ongoing nitrate therapy Concentric LV hypertrophy Critical aortic stenosis Long‐term use of medications that inhibit cytochrome P450 3A4 n = 34
Interventions	Sildenafil (25 to 75 mg orally 3 times daily) (N=17) or placebo (N=17)
Outcomes	6MWD Cardiopulmonary exercise test Haemodynamics using right‐heart catheterisation, including RAP, PCWP, CI, stroke volume, PVR, SVR Quality of life questionnaire including the Minnesota Heart Failure Questionnaire (a 21‐question self‐administered instrument in which scores can range from 0 to 5 for each question and higher scores indicate a poorer quality of life) Clinical worsening Mortality Adverse events
Notes	Public and industry funded Trial conducted at multiple centres (location not stated) from May 2003 to March 2006
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	The Massachusetts General Hospital Pharmacy was responsible for the blinding and randomisation procedure
Allocation concealment (selection bias)	Low risk	The Massachusetts General Hospital Pharmacy was responsible for the blinding and randomisation procedure
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Placebo‐controlled
Blinding of outcome assessment (detection bias) All outcomes	Low risk	The investigators adjudicated all primary and secondary endpoints and reviewed data on safety before unblinding of the study
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	It is not clear whether there were any withdrawals; does not explicitly state that all recruited completed the trial
Selective reporting (reporting bias)	Unclear risk	Prespecified outcomes were reported
Other bias	Low risk	Other bias is unlikely