Subjects ≥ 18
- Idiopathic Primary Pulmonary Arterial Hypertension (IPAH)
- PAH secondary to connective tissue disease
- PAH with surgical repair (at least 5 years previously) of atrial septal defect
(ASD),ventricular septal defect (VSD), patent ductus arteriosus (PDA) and
aorto-pulmonary window
- PAH diagnosis confirmed by right heart catheterization performed within 12 months
prior to randomization
- Functional Class II-IV; Baseline 6MWD ≥ 50 m.
- Significant (ie, >2+) valvular disease other than tricuspid regurgitation or pulmonary
regurgitation
- History of cardiac arrest, respiratory arrest, hemodynamic collapse, CPR, ventricular
tachycardia, ventricular fibrillation, or uncontrolled atrial fibrillation
- History of pulmonary embolism; History of chronic lung disease / restrictive lung
disease (eg, chronic obstructive pulmonary disease (COPD) or scleroderma) with
impairment of lung function
- No prior long term treatment with PDE-5 inhibitors
- Treatment with bosentan OR riociguat within 3 months of randomization
- Current treatment with nitrates or nitric oxide