Final answer:
High-risk PAH is defined by signs that predict higher mortality such as right heart failure and significant hemodynamic changes. The initial management includes supportive care and, if confirmed PAH, advanced therapies such as prostacyclin analogs and endothelin receptor antagonists.
Step-by-step explanation:
High risk Pulmonary Arterial Hypertension (PAH) is defined by a combination of clinical, hemodynamic, and imaging features that indicate a greater mortality risk. Patients with this classification often exhibit right heart failure symptoms, significantly elevated pulmonary vascular resistance, and reduced cardiac index. Initial management generally includes supportive therapies such as oxygen and diuretics. For patients with confirmed PAH, specific initial management may involve combinations of advanced therapies, including prostacyclin analogs, endothelin receptor antagonists, phosphodiesterase-5 inhibitors, and in some cases, the consideration for atrial septostomy or lung transplantation pending on the severity and response to medical therapy.