Heart failure with preserved ejection fraction (HFpEF) had been considered as a milder form of heart failure until 1990's. However, the prevalence and the prognosis of HFpEF were found to be similar to that of heart failure with reduced ejection fraction (HFrEF) and it is widely accepted that HFpEF is a separate entity of heart failure, substantially different from HFrEF. The pathophysiology of HFpEF can be contracted to the increased stiffness and impaired relaxation of left ventricle (LV), causing increased LV end-diastolic pressure and pulmonary venous pressure. These may lead to dyspnea, limited exercise capacity, and pulmonary congestion in patients.~Current guidelines on treatment of HFpEF include appropriate blood pressure control, rate control in those with atrial fibrillation, and use of diuretics for pulmonary or peripheral edema. But there has been no evidence-based effective treatment strategy for HFpEF. Recently, phosphodiesterase type 5 (PDE-5) inhibitors (eg. sildenafil, vardenafil, tadalafil) have shown promising effects on heart failure, reducing pulmonary vascular resistance, improving LV systolic and diastolic function, exercise capacity and quality of life. These results infer that PDE-5 inhibitors might be beneficial in patients with HFpEF.~Udenafil (Zydena), a newly developed PDE-5 inhibitor, has been proved to have similar efficacy and safety profile, compared with other PDE-5 inhibitors. Also, laboratory data showed that udenafil inhibits ventricular hypertrophy and fibrosis in rat heart failure model. Based on these results, we hypothesized that udenafil would improve symptom, exercise capacity and hemodynamic status in patients with HFpEF.~In this 12-week, randomized, double-blind, placebo-controlled trial, patients with HFpEF will be enrolled according to the eligibility criteria. After randomization, study participants will be assigned to receive either 50mg of udenafil or placebo two times a day for 4 weeks, and then the dosage will be doubled to 100mg two times a day for next 8 weeks. Participants will attend study visits at baseline and weeks 4 and 12. Physical examination, medical history review, blood sample collection and electrocardiogram will be conducted on each study visits. At baseline and week 12, participants will undergo cardiopulmonary exercise test and exercise echocardiography. At every study visits, researchers will collect health information.
The investigators hypothesized that udenafil, a newly developed phosphodiesterase type 5 inhibitor, would improve symptom, exercise capacity and hemodynamic status in patients with heart failure with preserved ejection fraction (HFpEF).