NPPB and pulmonary arterial hypertension: In the 2015 ESC/ERS guidelines for the diagnosis and treatment of PH, PAH patients were classified into low-risk, intermediate-risk, and high-risk groups based on clinical manifestations, symptom progression, syncopal attack, World Health Organization functional class (WHO-FC), 6 minute walk distance (6MWD), cardiopulmonary exercise test, plasma brain natriuretic peptide (BNP) or N-terminal (NT)-pro BNP (NT-proBNP) level, imaging examination, and hemodynamic characteristics of right heart failure, and their 1-year mortality rates were estimated to be <5%, 5–10%, and >10%, respectively [1].