NPPB and heart failure: Abbreviations: HFpEF: Heart Failure With Preserved Ejection Fraction, Lv: Left Ventricle, BNP: B-type (or Brain) Natriuretic Peptide, Nt-Pro BNP: N-terminal Pro-B-Type Natriuretic Peptide, E/E' Ratios: Ratio of Early Mitral Inflow Velocity (E) to Early Diastolic Mitral Annular Velocity (E'), Vo2: Oxygen Uptake (Volume of Oxygen Consumed per Minute), A-vO2Diff: Arteriovenous Oxygen Difference