NPPB and pulmonary arterial hypertension: Several non-invasive predictors are used to evaluate the prognosis of pulmonary hypertension (PH), i.e., New York Heart Association (NYHA) functional class, reduced 6-min walk test (6MWT), diffusing capacity for carbon monoxide (DLCO), and B-type natriuretic peptide (BNP) and the N-terminal fragment of pro-BNP (NT-pro-BNP) levels [4].