Brain natriuretic peptide (BNP) vs NT-proBNP

Brain natriuretic peptide (BNP) vs NT-proBNP

Brain natriuretic peptide (BNP) is secreted by ventricular myocardium in response to stretching of cardiomyocytes. BNP has vasodilative, diuretic and natriuretic activity and is a sensitive marker of left ventricular end-diastolic pressure. Pro-BNP is the precursor of BNP, which is enzymatically cleaved into an inactive amino terminal fragment known as NT-proBNP and a biologically active carboxyl terminal fragment called BNP.

NT-proBNP has a longer half-life (1-2 hours vs. 22 minutes) compared to BNP. Hence its blood levels are more stable and less influenced by acute haemodynamic variations than BNP levels. For this reason, it can reflect the mean values of left ventricular filling pressures over the previous 12 hours.

In a study conducted at City general hospital, Copenhagen, Denmark, 2230 admissions over a ten month period had echocardiographic evaluation and NT-proBNP estimation within 24 hours. A raised blood level of 357 pmol/l or more identified a left ventricular ejection fraction of 40% or lower with a sensitivity of 73% and specificity of 82% (n=157) [1]. Since the values can increase with age, and serum creatinine, a predicted value was calculated for each person. If the measured value was less than the predicted value, the probability of having a left ventricular ejection fraction above 40 percent was more than 97%.

Reference

1. Bay M, Kirk V, Parner J, Hassager C, Nielsen H, Krogsgaard K, Trawinski J, Boesgaard S, Aldershvile J. NT-proBNP: a new diagnostic screening tool to differentiate between patients with normal and reduced left ventricular systolic function. Heart. 2003 Feb;89(2):150-4.