In patients with cardiogenic pulmonary edema due to acute decompensated heart failure, plasma brain natriuretic peptide (BNP) measurements can guide the diagnosis, distinguishing this etiology of dyspnea from pulmonary causes. Plasma BNP concentration is elevated in both asymptomatic and symptomatic heart failure (left ventricular dysfunction) and is useful for both diagnosis and prognosis.

BNP is a hormone abundantly found in the heart (especially the ventricles) but initially identified in the brain. It is released from myocardial cells in response to wall stress, volume expansion, and high filling pressures. Physiologically, endogenously produced BNP targets the heart, blood vessels, and kidneys to reduce preload and afterload through vasodilatation, diuresis, and natriuresis (sodium excretion). BNP also counters neurohormones such as endothelin, aldosterone, and angiotensin II. Murine studies further suggest that BNP may protect against the progressive cardiac fibrosis associated with chronic heart failure. In whole, BNP reduces the workload on the heart to improve cardiac performance.

A rapid BNP fluorescence immunoassay was approved in 2000 and can be rapidly performed in 10 to 15 minutes at the bedside. Patients with heart failure have significantly higher levels of plasma BNP than those with dyspnea due to other causes. Remarkably, plasma BNP is more accurate for predicting heart failure than classic parameters such as rales, cardiomegaly, or the National Health and Nutrition Examination Survey (NHANES) or Framingham criteria. BNP also correlates with the New York Heart Association functional class. A value >100 pg/mL makes the diagnosis of heart failure with a sensitivity of 90%, specificity of 76%, and a predictive value of 83%. Conversely, low BNP has a strong negative predictive value to rule out heart failure. The rapid assay costs approximately $20 per test.