Brain natriuretic peptide

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In medicine, brain natriuretic peptide (BNP), also called B-Type natriuretic peptide, is a "peptide that is secreted by the brain and the heart atria, stored mainly in cardiac ventricular myocardium. It can cause natriuresis; diuresis; vasodilation; and inhibits secretion of renin and aldosterone. It improves heart function. It contains 32 amino acids."[1]

BNP is one member or a family of closely related peptides called "natriuretic peptides" because of their ability to stimulate sodium excretion (natriuresis). Natriuretic peptides are functional antagonists to the renin-angiotensin-aldosterone system. BNP was given its name because it was first discovered in the porcine brain. [2] However, confusingly, there appears to be relatively little BNP expressed in the brain compared to atrial natriuretic peptide [3] A related peptide is N-terminal pro-B-type natriuretic peptide.

An elevated concentration of BNP in the circulation can detect heart failure:[4] A recombinant DNA version of BNP, nesiritide (trade name Natrecor), is also given as a treatment for heart failure.

BNP test accuracy

Usig the BNP to detect heart failure[4]
  Sensitivity Specificity
BNP > 100 pg per milliliter 90% 76%
BNP > 50 pg per milliliter 97% 62%

The optimal level to exclude heart failure may depend on the clinical setting.[5]

A value over 400 suggests heart failure.[5] A value over 500 pg per milliliter is also proposed to indicate that heart failure is likely[6]; however, the accuracy of that value is not certain.

Effect on clinical decision making

Evaluation and management of acute dyspnea

Providing physicians quick access to BNP results may[7][6] improve the emergency evaluation of dyspnea.

Monitoring of chronic heart failure

Treating heart failure based on BNP might improve care according to a meta-analysis.[8] In one trail included in the meta-analysis, there was no improvement by treating for a goal of brain natriuretic peptide less than 400 pg/mL in patients younger than 75 years and less than 800 pg/mL in patients aged 75 years or older.[9] A second trial found uncertain benefit from targeting NT-proBNP level < 150 pmol/l.[10]

Targeting a clinical score to a score of 2 or less based on the Framingham diagnosis of heart failure with the following findings may[10] or may[11] not be similar to targeting BNP level.

Treatment with nesiritide

Nesiritide is considered adjunctive therapy for patients in severe heart failure, principally as a vasodilator, when neither nitroglycerine nor sodium nitroprusside provide sufficient benefit. Small studies suggest it may increase the risk of death, and further trials are underway. It has been suggested that intermittent intravenous infusion, as opposed to continuous microdrip administration, worsens the hazard. [12]

Clinical practice guidelines

Clinical practice guidelines state regarding the BNP and NT-proBNP:[13]

"Measurement of natriuretic peptides (BNP and NT-proBNP) can be useful in the evaluation of patients presenting in the urgent care setting in whom the clinical diagnosis of HF is uncertain. Measurement of natriuretic peptides (BNP and NT-proBNP) can be helpful in risk stratification."
"The value of serial measurements of BNP to guide therapy for patients with HF is not well established."

References

  1. Anonymous (2015), Brain natriuretic peptide (English). Medical Subject Headings. U.S. National Library of Medicine.
  2. Baxter GF (2004) The natriuretic peptides. Basic Res Cardiol 99:71-5. PMID 14963664
  3. Langub MC et al. (1995) Distribution of natriuretic peptide precursor mRNAs in the rat brain. J Comp Neurol 356:183-99. PMID 7629314
  4. 4.0 4.1 Maisel AS, Krishnaswamy P, Nowak RM, et al (July 2002). "Rapid measurement of B-type natriuretic peptide in the emergency diagnosis of heart failure". N Engl J Med 347: 161–7. DOI:10.1056/NEJMoa020233. PMID 12124404. Research Blogging.
  5. 5.0 5.1 Rogers RK, Stoddard GJ, Greene T, Michaels AD, Fernandez G, Freeman A et al. (2009). "Usefulness of adjusting for clinical covariates to improve the ability of B-type natriuretic peptide to distinguish cardiac from noncardiac dyspnea.". Am J Cardiol 104 (5): 689-94. DOI:10.1016/j.amjcard.2009.04.043. PMID 19699346. Research Blogging.
  6. 6.0 6.1 Schneider HG, Lam L, Lokuge A, et al. (March 2009). "B-type natriuretic peptide testing, clinical outcomes, and health services use in emergency department patients with dyspnea: a randomized trial". Ann. Intern. Med. 150 (6): 365–71. PMID 19293069[e]
  7. Mueller C, Scholer A, Laule-Kilian K, et al. (February 2004). "Use of B-type natriuretic peptide in the evaluation and management of acute dyspnea". N. Engl. J. Med. 350 (7): 647–54. DOI:10.1056/NEJMoa031681. PMID 14960741. Research Blogging.
  8. Porapakkham P, Porapakkham P, Zimmet H, Billah B, Krum H (2010). "B-Type Natriuretic Peptide-Guided Heart Failure Therapy: A Meta-analysis.". Arch Intern Med 170 (6): 507-14. DOI:10.1001/archinternmed.2010.35. PMID 20308637. Research Blogging.
  9. Pfisterer M, Buser P, Rickli H, et al (January 2009). "BNP-guided vs symptom-guided heart failure therapy: the Trial of Intensified vs Standard Medical Therapy in Elderly Patients With Congestive Heart Failure (TIME-CHF) randomized trial". JAMA 301 (4): 383–92. DOI:10.1001/jama.2009.2. PMID 19176440. Research Blogging.
  10. 10.0 10.1 Lainchbury JG, Troughton RW, Strangman KM, Frampton CM, Pilbrow A, Yandle TG et al. (2009). "N-terminal pro-B-type natriuretic peptide-guided treatment for chronic heart failure: results from the BATTLESCARRED (NT-proBNP-Assisted Treatment To Lessen Serial Cardiac Readmissions and Death) trial.". J Am Coll Cardiol 55 (1): 53-60. DOI:10.1016/j.jacc.2009.02.095. PMID 20117364. Research Blogging.
  11. Troughton RW, Frampton CM, Yandle TG, Espiner EA, Nicholls MG, Richards AM (2000). "Treatment of heart failure guided by plasma aminoterminal brain natriuretic peptide (N-BNP) concentrations.". Lancet 355 (9210): 1126-30. PMID 10791374.
  12. Natrecor IV, American Society of Health-System Pharmacists
  13. Hunt SA, Abraham WT, Chin MH, Feldman AM, Francis GS, Ganiats TG et al. (2009). "2009 focused update incorporated into the ACC/AHA 2005 Guidelines for the Diagnosis and Management of Heart Failure in Adults: a report of the American College of Cardiology Foundation/American Heart Association Task Force on Practice Guidelines: developed in collaboration with the International Society for Heart and Lung Transplantation.". Circulation 119 (14): e391-479. DOI:10.1161/CIRCULATIONAHA.109.192065. PMID 19324966. Research Blogging.