NPPB and pericardial effusion: The first REVEAL risk calculator was developed by Benza et al. (10) in 2012 and consisted of twelve variables: WHO Functional Class (WHO-FC), 6-minute walk distance (6MWD), N-terminal-pro brain natriuretic peptide (NT-proBNP, or brain natriuretic peptide–BNP), pericardial effusion, mRAP, pulmonary vascular resistance (PVR), WHO group 1 subgroup, male older than 60 years of age, renal insufficiency, systolic blood pressure (SBP), heart rate (HR), and percentage predicted carbon monoxide lung diffusing capacity (DLCO).