N terminal pro-brain natriuretic peptide levels are elevated in:: (A) Atrial fibrillation, (B) Left heart failure, (C) Pulmonary thromboembolism, (D) Myocardial infarction
Answer is B. In left heart failure, left ventricle releases N terminal pro-BNP and it is used as a marker for left ventricular failure.
Measurement of brain natriuretic peptide levels in serum is increasingly used to assess for CHF in patients presenting with acute dyspnea, but may be elevated in the presence of right ventricular strain as well.
Plasma levels of N-terminal pro brain natriuretic peptide moderately correlate with carcinoid heart disease severity.
Reference: Harrison’s P R I N C I P L E S   O F I N T E R N A L M E D I C I N E 20th edition page no 1740,