B-Type Natriuretic Peptide (BNP)

B-type natriuretic peptide (BNP), also referred to as brain natriuretic peptide, is a member of a family of structurally similar peptide hormones that includes atrial natriuretic peptide.¹ BNP is a 32-amino-acid peptide that contains a 17-amino-acid ring structure that is formed as the result of an internal disulfide bond. BNP is predominantly secreted by the ventricles of the heart in response to increased pressure. BNP acts as a vasodilator and has diuretic and natriuretic properties. BNP suppresses both sympathetic tone and the renin-angiotensin system. These physiologic effects serve to reduce intraventricular pressure and improve the symptoms of congestive heart failure (CHF).

BNP levels increase with age and can be transiently increased by vigorous exercise.^1,2 BNP levels correlate with end-diastolic pressure and tend to be increased in patients with diminished left ventricular ejection fraction.^1,3 BNP levels have been shown to be useful in the diagnosis of patients with symptoms that are consistent with CHF. Maisel and coworkers⁴ found that a BNP cutoff of 75 pg/mL could be used to predict systolic and/or diastolic abnormalities accurately in symptomatic patients referred to echocardiology for left ventricular function studies. They found that this cutoff identified patients with abnormal function from a population of 200 patients with a sensitivity of 95.9%, specificity of 86%, positive predictive value of 98%, and a negative predictive value of 89%. The overall accuracy of the diagnosis with a cutoff of 75 pg/mL was 93%. These results were similar to those found by Dao and coworkers.⁵ They found that BNP levels could be used to accurately identify patients with CHF from a population of patients presenting at the emergency room with shortness of breath (dyspnea). They found that a BNP value >80 pg/mL could be used to identify patients with CHF from this population with a sensitivity of 97%, specificity of 98%, positive predictive value of 92%, and a negative predictive value of 98%.⁶