BACKGROUND Over the last few years, the use of phosphodiesterase type 5 (PDE5) inhibitors has been expanded to management of various cardiovascular disorders beyond pulmonary arterial hypertension. This study is designed to investigate the ability of udenafil, a newly developed long-acting PDE5 inhibitor, to improve functional capacity and hemodynamic status in a cohort of chronic systolic heart failure (SHF) patients.

METHODS/DESIGN Stable, chronic SHF patients will be randomly assigned to placebo (26 patients) or udenafil at a dose of 50 mg twice per day (26 patients) for the first 4 weeks followed by 100 mg twice daily for the next 8 weeks. Eligibility criteria will be age ≥ 18 years, clinical diagnosis of chronic SHF with current New York Heart Association class II to IV symptoms, left ventricular ejection fraction ≤ 40%, and experience of at least one of following during the 12 months prior to study entry: hospitalization for decompensated heart failure, acute treatment with intravenous loop diuretics or hemofiltration, or pulmonary artery systolic pressure ≥ 40 mmHg on transthoracic echocardiography. Pharmacological therapy for SHF will be optimized in all patients at least 30 days before study entry. The primary outcome will be the change of maximal oxygen uptake, assessed by cardiopulmonary exercise testing. Secondary outcomes will include changes in ventilatory efficiency (minute ventilation/carbon dioxide production slope), left ventricular systolic and diastolic parameters, pulmonary artery systolic pressure, plasma concentration of brain natriuretic peptide, occurrence of mortality or hospitalization for heart failure, and the occurrence of any adverse event.

CLINICAL TRIAL REGISTRATION Unique identifier: NCT01646515.