NPPB and pulmonary arterial hypertension: Six-minute walk distance (6MWD), functional class (FC), and indicators of right ventricular function (i.e., brain natriuretic peptide [BNP]/the active N-terminal cleavage product of its prohormone [NT-proBNP], described in Table 1) are among the commonly used short-term primary and secondary noninvasive endpoints in clinical PAH trials [9, 10].