text: PDE5 inhibitors have shown promise in the treatment of heart failure with reduced ejection fraction through several beneficial effects on lung vasculature, cardiac remodelling and diastolic function. A study showed that effective treatment of pulmonary arterial hypertension with sildenafil improved functional capacity and reduced right ventricular mass in patients. The effects on right ventricular remodeling were significantly greater in comparison with the non-selective endothelial receptor antagonist bosentan. However, PDE5 inhibitors may be harmful in patients with heart failure with preserved ejection fraction due to potential negative inotropic effects.