Introduction

B-type natriuretic peptide (BNP) is a hormone produced mainly by the left ventricular myocardium in response to strain.

Whilst heart failure is the most obvious cause of raised BNP levels any cause of left ventricular dysfunction such as myocardial ischaemia or valvular disease may raise levels. Raised levels may also be seen due to reduced excretion in patients with chronic kidney disease. Factors which reduce BNP levels include treatment with ACE inhibitors, angiotensin-2 receptor blockers and diuretics.

Effects of BNP
  • vasodilator
  • diuretic and natriuretic
  • suppresses both sympathetic tone and the renin-angiotensin-aldosterone system

Indications

Diagnosing patients with acute dyspnoea
  • a low concentration of BNP(< 100pg/ml) makes a diagnosis of heart failure unlikely, but raised levels should prompt further investigation to confirm the diagnosis
  • NICE currently recommends BNP as a helpful test to rule out a diagnosis of heart failure

Prognosis in patients with chronic heart failure
  • initial evidence suggests BNP is an extremely useful marker of prognosis

Guiding treatment in patients with chronic heart failure
  • effective treatment lowers BNP levels

Screening for cardiac dysfunction
  • not currently recommended for population screening

Interpretation

NICE issued updated guidelines on diagnosis and management in 2018. Previously the first-line investigation was determined by whether the patient has previously had a myocardial infarction or not this is no longer the case - all patients should have an N-terminal pro-B-type natriuretic peptide (NT‑proBNP) blood test first-line.

Interpreting the test
  • if levels are 'high' arrange specialist assessment (including transthoracic echocardiography) within 2 weeks
  • if levels are 'raised' arrange specialist assessment (including transthoracic echocardiography) echocardiogram within 6 weeks

Serum natriuretic peptides

B-type natriuretic peptide (BNP) is a hormone produced mainly by the left ventricular myocardium in response to strain. Very high levels are associated with a poor prognosis.

BNP NTproBNP
High levels> 400 pg/ml (116 pmol/litre)> 2000 pg/ml (236 pmol/litre)
Raised levels100-400 pg/ml (29-116 pmol/litre)400-2000 pg/ml (47-236 pmol/litre)
Normal levels< 100 pg/ml (29 pmol/litre)< 400 pg/ml (47 pmol/litre)

Factors which alter the BNP level:

Increase BNP levelsDecrease BNP levels
Left ventricular hypertrophy
Ischaemia
Tachycardia
Right ventricular overload
Hypoxaemia (including pulmonary embolism)
GFR < 60 ml/min
Sepsis
COPD
Diabetes
Age > 70
Liver cirrhosis
Obesity
Diuretics
ACE inhibitors
Beta-blockers
Angiotensin 2 receptor blockers
Aldosterone antagonists