- A Pulmonary Vascular Resistance (PVR) ≥ 800 dynes.sec.cm-5 (as assessed by Right Heart Catheterization (RHC) at screening or in the 3 months preceding the screening visit) despite treatment with two or more specific PAH therapies, including Endothelin Receptor Antagonists (ERAs), phosphodiesterase 5 inhibitors (PDE5), or subcutaneous, inhaled, intravenous or oral prostacyclin analogues for ≥ 3 months. Background therapy doses were to be stable for ≥ 30 days except for warfarin and prostacyclin analogues ( ≥ 30 days but doses could vary even within the month before enrollment).