Pulmonary Arterial Hypertension Market by Drug Class (Endothelin Receptor Antagonists (ERAs), Prostacyclin and Prostacyclin Analogs, Phosphodiesterase-5 (PDE-5) Inhibitors, and Soluble Guanylate Cyclase (sGC) Stimulators); By Application (Hospitals, Clinics, and Others); By Geography (North America, Asia-Pacific, Europe, South America, and RoW), Industry Trends, Estimation & Forecast, 2018 – 2026