Index
Also known as NPPB or BNP, it is a secreted protein that works like a heart hormone.
It is secreted from the gene of the same name and has a number of biological functions.
These include natriuresis , the excretion of sodium in the urine, as well as diuresis, the increased production of urine. These functions help balance salt and water in the body.
Other effects include vasorelaxation , which helps lower blood pressure, as well as inhibits renin and aldosterone secretion. NPPB also plays a role in cardiovascular homeostasis, in other words, keeping the heart healthy and stable.
Levels of brain natriuretic peptide (BNP) are markedly increased in left ventricular dysfunction, and the level in heart failure correlates with the severity of symptoms. Therefore, BNP may be an important clinical marker for the diagnosis of heart failure in patients with unexplained dyspnea.
Other clinical applications, such as screening for asymptomatic ventricular dysfunction, establishing prognosis or guiding drug treatment titration, and predicting future cardiovascular events, are being investigated but have not yet been sufficiently validated for widespread clinical use. .
BNP is a 32 amino acid biologically active peptide and has vasodilator and natriuretic properties.
BNP is cleaved from the 108 amino acid brain natriuretic peptide released from the cardiac ventricles in response to stretching of the chamber.
The second remnant after cleavage, the N-terminal pro-brain natriuretic peptide (NT-proBNP), is a 76 amino acid peptide with no known biological function that circulates at higher concentrations than BNP and can represent cardiac status for longer periods. long.
BNP release appears to be in direct proportion to ventricular volume expansion and pressure overload. BNP increases with right or left systolic or diastolic heart failure.
It is an independent predictor of left ventricular end-diastolic pressure. BNP levels decrease after effective treatment of heart failure.
Although BNP tests provide a useful adjunct to routine evaluation to differentiate acute heart failure from other causes of dyspnea, other factors such as comorbid conditions, age, chronic kidney disease, and body mass can affect BNP levels.
In these cases the diagnosis of heart failure can obscure, particularly when this marker is used in isolation.
Therefore, it is essential that BNP be used to aid diagnosis, in addition to the patient’s history, clinical signs, and other investigations. The role of BNP in heart failure and whether it is a target to treat or a risk identifier remain controversial.
Measure
There is currently no definitive evidence of a clinical advantage between the use of a BNP assay or the NT-proBNP assay.
- The most commonly used decision threshold for BNP is 100 pg / ml.
- BNP levels greater than 100 pg / ml have a specificity greater than 95% and a sensitivity greater than 98% when comparing patients without congestive heart failure (CHF) with all patients with congestive heart failure.
- Even BNP levels of more than 80 pg / ml have a specificity greater than 93% and a sensitivity of 98% in the diagnosis of heart failure.
- BNP levels increase with age. Average BNP levels are: 26.2 pg / ml in people 55-64 years old, 31.0 pg / ml in people 65-74 years old, and 63.7 pg / ml in people older than 75 years.
- Women without CHF tend to have higher BNP levels than men of the same age.
- Patients must have had an ECG, CXR, FBC, renal function and electrolyte tests, LFT, lipid profile, TFT, and any other investigation relevant to the clinical presentation.
Possible causes of elevated brain natriuretic peptide levels
Cardiac
- Heart failure.
- Diastolic dysfunction.
- Acute coronary syndromes.
- Hypertension with left ventricular hypertrophy.
- Valvular heart disease (aortic stenosis, mitral valve regurgitation).
- Atrial fibrillation
Non-cardiac
- Acute pulmonary embolism.
- Pulmonary hypertension (primary or secondary).
- Sepsis (possibly due to tissue hypoxia or secondary myocardial depression).
- Chronic obstructive pulmonary disease with cor pulmonale or respiratory failure.
- Hyperthyroidism
- Acute or chronic kidney injury.
BNP levels may be lower than expected when heart failure is secondary to causes close to the left ventricle, for example, acute mitral regurgitation, mitral stenosis, or atrial myxoma .
Potential Use of Brain Natriuretic Peptide Measurement
Heart failure
The BNP assay is a potential aid in the diagnosis of heart failure.
The BNP test allows rapid evaluation to define patients who require an echocardiogram and also has the potential to allow rapid changes in therapy for those already receiving treatment for heart failure.
- The BNP test is effective in screening for left ventricular systolic dysfunction and reduces the number of patients requiring an echocardiogram.
- Normal levels virtually exclude the diagnosis of heart failure, and very high levels effectively diagnose the condition; intermediate values require further evaluation.
- The BNP assay has potential as part of a diagnostic triage in patients presenting with symptoms suggestive of heart failure or in screening high-risk populations.
- In several pilot studies, BNP levels had a strong correlation with disease severity and were highly reliable in differentiating heart failure from lung disease.
- A pilot study has reviewed the role of fingerstick tests for BNP at home and its usefulness in detecting decompensation. They found that BNP changes did help determine the risk of decompensation and should complement other clinical markers of decompensation.
In a pilot study, BNP levels were highly correlated with clinical outcomes:
- Patients with decreased BNP levels during their hospital stay, along with decreases in the NYHA rating, did well.
- Patients whose hospital stay ended in death or readmission within 30 days of discharge had minimal decline in BNP levels or increased BNP levels despite improvement or no change in their NYHA classification .
- The last measured BNP level was the most reliable variable for predicting short-term outcomes in heart failure patients.
Other potential clinical applications
- Elevated plasma natriuretic peptide levels have been shown to predict the risk of death and cardiovascular events in people without heart failure after adjustment for traditional risk factors.
- The excess risk was evident in natriuretic peptide levels well below current thresholds used to diagnose heart failure.
- Natriuretic peptides can help identify people at risk for stroke and atrial fibrillation.
- BNP is a powerful independent marker of early and late cardiac mortality in patients with acute chest pain without ST-segment elevation.
