RecruitingPhase 3Drug trialTrial to Evaluate Parenteral Treprostinil and Riociguat on Right Ventriculo-vascular Coupling and Morphology in Those With Advanced PAHThe purpose of this study is to determine if there is a greater effect to patients with advanced pulmonary arterial hypertension (PAH) by using a combination of two drugs, Treprostinil and Riociquat versus Treprostinil alone