These recommendations reflect those made by the National Institute for Health and Clinical Excellence (NICE) in their guideline Chronic heart failure: national clinical guideline for diagnosis and management in primary and secondary care [National Clinical Guideline Centre for Acute and Chronic Conditions, 2010], as well as guidelines from the Scottish Intercollegiate Guidelines Network (SIGN) [SIGN, 2007] and European specialist society guidelines [European Society of Cardiology, 2008].

Electrocardiography (ECG)

• There is evidence that ECG can provide diagnostically useful information, such as presence of atrial fibrillation, new T-wave changes, ST-segment elevation or depression, pathological Q-waves, left bundle-branch block, and left ventricular hypertrophy. In particular, a normal ECG has reasonable negative predictive value for heart failure. A recent Health Technology Appraisal found that a completely normal ECG can help to rule out the diagnosis of heart failure, but the presence of any abnormality does not help to rule in the diagnosis of heart failure [Mant et al, 2009].

Chest X-ray

• There is evidence from systematic reviews that chest X-ray can provide diagnostically useful information, such as the presence of pulmonary venous congestion, interstitial oedema, alveolar oedema, cardiomegaly, and pleural effusion, but most of the studies included in the systematic reviews were conducted in hospital, where people were likely to be more severely ill than people managed in primary care. A recently published Health Technology Assessment found that an abnormal chest X-ray is moderately helpful for ruling the diagnosis in, but a normal chest X-ray cannot rule out the diagnosis (moderately specific but poorly sensitive).

Natriuretic peptides

• Measurement of natriuretic peptide levels helps to determine:
• The likelihood of the presence of heart failure.
• The need for referral for specialist assessment and confirmation of the diagnosis by echocardiography.
• The urgency of the referral.
• Two types of natriuretic peptide can be measured: B-type natriuretic peptide (BNP) and N-terminal pro-BNP (NT-proBNP). NT-proBNP is the inactive prohormone of BNP and is secreted from the ventricles in response to volume expansion and pressure overload (as occurs in heart failure). BNP increases renal excretion of sodium (natriuresis) and water (diuresis) and relaxes vascular smooth muscle, which leads to vasodilation.
• Increased levels of BNP or NT-proBNP are not on their own diagnostic of heart failure, because levels may be raised in people with left ventricular hypertrophy, myocardial ischaemia, atrial fibrillation, pulmonary hypertension, hypoxia, pulmonary embolism, right ventricular strain, chronic obstructive pulmonary disease, liver failure, sepsis, diabetes, and renal impairment. In addition, levels tend to be higher in people older than 70 years of age and in women.
• Levels are lower in people who are obese or are taking drug treatments, such as aldosterone antagonists, angiotensin-converting enzyme inhibitors, angiotensin-II receptor antagonists, beta-blockers, and diuretics.
• Good evidence supports the use of BNP and NT-proBNP tests in excluding heart failure. NICE found evidence from a Health Technology Assessment that although elevated levels of BNP and NT-proBNP do not confirm the diagnosis of heart failure, normal levels rule the diagnosis out (BNP and NT-proBNP are highly sensitive but have varying specificity). In addition, the accuracy of both tests was found to be similar, and BNP had greater diagnostic accuracy than ECG.
• NICE recommends that measurement of natriuretic peptide is not necessary in people with suspected heart failure and previous myocardial infarction — all such people require urgent referral (to be seen within 2 weeks) for echocardiography and specialist assessment, because if heart failure is present their prognosis is poor.

Diagnostic strategy

• CKS found no evidence on how best to sequence diagnostic tests. CKS recommendations reflect the guidelines published by NICE [National Clinical Guideline Centre for Acute and Chronic Conditions, 2010] and other organizations [SIGN, 2007; European Society of Cardiology, 2008]. The recommendations on diagnostic strategy are based on expert opinion within these guideline development groups.