What does BNP (B-type natriuretic peptide) indicate?

B-type natriuretic peptide (BNP) is a neurohormone produced by the heart, particularly by the ventricles, in response to increased pressure that typically accompanies heart failure. Elevated levels of BNP indicate that the heart is experiencing increased wall stress due to volume overload or increased pressure, which occurs when the heart's ability to pump effectively is compromised.

In cases of heart failure, as the heart struggles to maintain adequate circulation, the muscle fibers within the ventricles become distended, leading to the release of BNP into the bloodstream. Therefore, a high level of BNP is a reliable marker for diagnosing heart failure and assessing its severity. The correlation between BNP levels and cardiac wall stress is significant; the higher the BNP, the greater the stretch and stress on the heart's walls.

Other options, while related to cardiac function, do not directly represent what BNP indicates. For example, while decreased cardiac output may occur in heart failure, BNP more specifically reflects the response of the ventricles to increased stress. The presence of cardiac enzymes typically relates to acute myocardial infarction rather than heart failure, and dehydration is not associated with elevated BNP levels. Thus, increased cardiac wall stretch and stress is the most accurate interpretation of elevated BNP levels, making