Heart failure is a complex syndrome that can result from any structural or functional cardiac disorder that impairs the ability of the heart to function as a pump and to support its physiological circulation (NICE guidelines). The syndrome of heart failure is characterised by symptoms such as breathlessness, fatigue and signs such as fluid retention. Diagnosing heart failure is not straightforward and requires a series of complex investigations along with clinical evaluation to arrive at that decision.
It is one of the most common conditions in industrialised society today- in the UK around 900,000 people have heart failure with a further similar number who have yet to develop symptoms (Peterson et al, British Heart Foundation 2002, cited in Full NICE guidelines). The most common cause of heart failure in the UK is coronary heart disease with many patients having suffered a myocardial infarction in the past. There is no single diagnostic test for heart failure and diagnosis is realised on clinical judgement based on a combination of history, full examination and appropriate investigations.
There are two main types of BNP that are available for testing. The first is brain-type natriuretic peptide i.e. BNP, which plays an important role in regulation of blood pressure, blood volume and sodium balance. Once secreted the BNP precursor is split into biologically active peptide and the second type of BNP, the more stable amino-terminal prohormone fragment NT-proBNP, is secreted.
It is already known that N-terminal proB-type natriuretic peptide (NT-proBNP) levels provide sensitive and reasonably specific tests for diagnosis of heart failure and left ventricular dysfunction (Cowie et al, 1997: Talwar et al, 1999: Maisel et al, 2002: Moe 2005, cited in Heart Protection Study Group, 2007). Furthermore, it is highly recommended also in NICE guidelines, and its results provide a good indicator of disease activity and prognosis of patients with heart failure.