B Type Natriuretic Peptide (BNP)

BNP is produced by cardiac myocytes in response to stretch which occurs in impaired diastolic or systolic function. BNP may play an important role in acute cardiac failure. BNP assays can supplement clinical judgment when the cause of a patient’s dyspnoea is uncertain. Results should be interpreted in the context of all available clinical data. The role of BNP in chronic heart failure is, however, well established for diagnosing, staging and risk stratifying patients. [9]

BNP has reasonable sensitivity and therefore can be used to rule out heart failure as a cause of a patient’s breathlessness (in a primary care setting for example) but it is not very specific and therefore not useful for ruling the diagnosis in.  BNP rises due to sepsis, renal or liver failure, hypoxia, myocardial ischaemia, tachycardia as well as many other reasons.  In hyperacute or “flash” pulmonary oedema or acute mitral regurgitation the BNP level may not be elevated initially.