From the Guidelines
A low BNP level is a strong indicator that heart failure is unlikely to be the cause of a patient's symptoms, and alternative diagnoses should be considered. This is based on the most recent and highest quality study available, which found that B-type natriuretic peptide (BNP) and N-terminal probrain natriuretic peptide (NT-proBNP) have excellent ability to exclude the diagnosis of acute heart failure at their respective lower cut-off thresholds, with sensitivities approaching 1 1. When interpreting BNP levels, it is essential to consider the clinical context, as certain factors can affect BNP levels, such as obesity, advanced age, and kidney disease. Some key points to consider when evaluating a low BNP level include:
- A low-normal concentration in an untreated patient makes heart failure unlikely as the cause of symptoms 1
- BNP and NT-proBNP have considerable prognostic potential, although evaluation of their role in treatment monitoring remains to be determined 1
- The diagnostic potential of natriuretic peptides is less clear cut when systolic function is normal, but there is increasing evidence that their elevation can indicate diastolic dysfunction is present 1
- Other common cardiac abnormalities that may cause elevated natriuretic peptide levels include left ventricular hypertrophy, valvular heart disease, acute or chronic ischaemia or hypertension, and pulmonary embolism 1
- The early use of a natriuretic peptide test to rule out acute heart failure, at the diagnostic thresholds evaluated in this meta-analysis, can reliably exclude heart failure and allow more rapid investigation of other potential causes for a patient’s symptoms 1. No specific treatment is needed for a low BNP, as it represents a normal physiological state, but the underlying cause of symptoms should still be investigated.
From the Research
Significance of Low BNP Levels
- Low BNP levels can be observed in patients with heart failure, despite expectations of high BNP levels in such conditions 2
- A low BNP level may be indicative of a "NP deficiency," which can render individuals more susceptible to volume or pressure overload 2
- Higher body mass index is a strong predictor of unexpectedly low BNP levels 2
- Low BNP levels have been associated with poor clinical outcomes in patients with chronic and advanced heart failure 3
- In patients with acute heart failure, low NT-proBNP levels may be an early sign of ischemic heart failure, particularly in those with normal left ventricular ejection fraction (LVEF) and shorter time from symptom onset to emergency department visit 4
Clinical Implications
- Low BNP levels may not always be a reliable indicator of heart failure severity or prognosis 2, 3
- The use of beta-blockers, angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, and mineralocorticoid receptor antagonists may have varying effects on heart failure outcomes, including mortality and hospitalization rates 5, 6
- Further research is needed to understand the significance of low BNP levels in different patient populations and to identify the most effective treatment strategies for heart failure with preserved ejection fraction (HFpEF) 6