Heart failure: clinical features and diagnosis

Heart failure is a clinical syndrome characterised by the inability of the heart to maintain sufficient cardiac output to meet the metabolic demands of the tissues.

The condition can affect people regardless of age, gender, ethnicity or social background. In developed countries, heart failure affects 1–2% of the population with the prevalence rising to over 10% in those aged over 70 years^[1]
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There are an estimated 900,000 heart failure patients in the UK today and prevalence is predicted to increase as comorbidities, such as hypertension, diabetes, atrial fibrillation and obesity, continue to rise and people begin to live longer with the disease.

Disease burden

The cost of heart failure treatment and care accounts for 2% of the NHS budget — which amounts to roughly £2bn of the £98bn total budget for 2014–15 — of which 70% is spent on hospital care.

One million inpatient bed-days and 5% of all emergency medical admissions are linked to heart failure^[2]
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According to data from the Health and Social Care Information Centre, there were 63,110 hospital admissions for heart failure in 2012–13 (90% of cases were emergencies) and the mean length of stay was 10.9 days^[4]
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Recurrent admissions are common with one in four patients readmitted to hospital within three months of discharge.

Optimising pharmacological therapy for patients with heart failure could produce substantial savings by preventing admissions to hospital, reducing length of stay, avoiding readmissions and delaying disease progression, thus postponing the need for more expensive forms of treatment.

Causes

Many conditions have been linked with the development of heart failure (see Box 1). Moreover, the occurrence of multiple comorbidities can have an impact on both the development and management of the disease. Identifying the cause of heart failure is vital for establishing an appropriate management plan. Furthermore, the timely identification and treatment of correctable causes can allow some underlying cardiac abnormalities to resolve — resulting in partial or complete recovery^[5]
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Clinical features

Shortness of breath, ankle or foot swelling and tiredness are commonly reported by patients with heart failure. Although these symptoms are not exclusive to the condition, they can be used to assess the likelihood of cardiac failure and indicate whether or not more specific investigations are needed. There are certain signs that are highly specific to heart failure and in the absence of more than one of these signs, a diagnosis of heart failure is unlikely.

Although the causes and clinical features of left and right ventricular failure are largely the same, left-sided heart failure is mainly associated with fatigue and breathlessness (caused by reduced cardiac output and pulmonary congestion) and right-sided heart failure typically causes peripheral oedema and raised jugular venous pressure^[6]
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The term “chronic heart failure” is used to describe the presence of the syndrome over a prolonged period. When signs and symptoms remain unchanged for four weeks or more the patient is generally considered to be stable. Symptomatic deterioration indicates the onset of decompensation. Depending on the triggering factor, the appearance of symptoms and signs can occur rapidly (ie, acute heart failure) or progressively.

Diagnosis

Collecting information about a patient’s social background, such as age, employment, family situation and living arrangements can provide information about potential occupational causes of symptoms and help the clinician assess the level of support the patient has at home. Information regarding smoking habits, alcohol consumption and use of recreational drugs can also aid diagnosis. An accurate medication history can help identify any potential pharmacological causes of heart failure (eg, clozapine).

Family history of premature death or early onset cardiac disease is also important to document, especially for younger patients.

Heart failure can affect the left or right ventricle together (biventricular failure) or exclusively, and the failing of one ventricle can cause the other to malfunction, too. The causes of left and right ventricular failure are largely the same and the diagnostic tests described below can detect either one.

Heart failure associated with left-ventricular systolic dysfunction due to suboptimal contraction, termed “systolic heart failure”, has long been considered the main type of heart failure. However, not all patients present with systolic dysfunction and, in such cases, it is the impaired relaxation of the left ventricle — ie, diastolic dysfunction — that causes symptoms to manifest. This has often been termed “diastolic heart failure”. Diastolic dysfunction is more difficult to assess and can occur alongside systolic dysfunction; therefore, diagnosis is not always straightforward or accurate.

Cardiac imaging

Echocardiography is the primary cardiac imaging technique used for assessing heart failure. It uses ultrasound to evaluate the structure and function of the cardiac chambers, valves and pericardium^[8]
. Diagnosing heart failure requires an assessment of the left-ventricular systolic and diastolic function, detection of valvular disease or intracardiac shunts and structural and motional abnormalities.

Echocardiograms are performed by appropriately trained operators using high-resolution equipment. Transthoracic doppler two-dimensional echocardiography is the recommended method of imaging because it is widely available, portable, safe and inexpensive. Transoesophageal echocardiography may be used instead if the quality of images is poor, which may be the case in people with obesity or chronic lung disease, or if ventilatory support is being used.^1,2  

A vital parameter in the assessment of heart failure is left-ventricular ejection fraction (EF), which represents the capacity of the left ventricle to push blood through the systemic circulation. Left-ventricular EF can be affected by changes to preload, afterload, heart rate, ventricular volume and valvular function.

The American College of Cardiology and American Heart Association⁸ use EF to distinguish between the different types of heart failure, as does the European Society of Cardiology. ACC/AHA 2013 guidelines state that, for patients who have been clinically diagnosed with heart failure, those with an EF of 50% or more are diagnosed with heart failure with preserved EF (HFPEF), those with an EF of 41–49% are considered to have borderline HFPEF and those with an EF of less than 40% are categorised as having heart failure with reduced EF (HFREF).

European Society of Cardiology 2012 guidelines¹ assign a diagnosis of HFREF to patients who have signs and symptoms typical of heart failure and a reduced ejection fraction (no set numeric parameters). Patients are considered to have HFPEF if they have signs and symptoms typical of heart failure, a normal or mildly reduced EF without left ventricular dilatation and if there is presence of structural heart disease with or without diastolic dysfunction.

The National Institute for Health and Care Excellence does not outline specific criteria for HFREF and HFPEF because the accurate estimation of ejection fraction depends on the imaging technique used and there is no universal agreement on the threshold between the two types. Instead, NICE stipulates that, for an accurate diagnosis to be made, patients with suspected heart failure should have an echocardiogram and be assessed by a specialist.²

Other imaging techniques, such as cardiac magnetic resonance imaging, heart catheterisation and coronary angiography, are generally reserved to diagnose underlying conditions in selected patients.

Natriuretic peptides

Natriuretic peptides are hormones that are secreted as a result of myocardial damage or excessive strain on the cardiac chambers.1 B-type natriuretic peptide (BNP) and the N-terminal pro-B-type natriuretic peptide (NT-proBNP) can both be used for diagnostic purposes. NT-proBNP has a longer biological half-life and greater stability in vitro^[9]
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NICE recommends that natriuretic peptide testing be used as a “rule-out test” for heart failure³ . Normal levels, ie, BNP <100pg/ml or NT-pro-BNP <400pg/ml, have a high negative predictive value and essentially exclude heart failure of any type^1,2,5 (provided the patient is not already on treatment, in which case a false negative is possible). High levels of serum natriuretic peptides (BNP >400pg/ml or NT-pro-BNP >2,000pg/ml) are associated with a poor prognosis.²

The serum concentrations of natriuretic peptides vary depending on the onset of heart failure and the values stated should be used only when chronic heart failure is suspected. NICE is currently developing a guideline for the diagnosis and management of acute heart failure (due to be published in September 2014), which may stipulate different reference values.

Levels of natriuretic peptides can also be increased or decreased by factors other than heart failure, such as comorbidities or medicines. For example, chronic obstructive pulmonary disease and renal dysfunction can increase levels, whereas obesity and diuretic use can decrease levels. Therefore, analysing natriuretic peptide levels alone does not provide enough evidence to diagnose heart failure.

Electrocardiogram

The electrocardiogram (ECG) is an easy, cheap and accessible investigation that can be performed routinely in many care settings. ECGs can provide information on the rhythm and propagation of electrical impulses through the heart conduction system. They can aid differential diagnosis and identification of causes and decompensation. Many different, although non-specific, ECG abnormalities can be present in heart failure; if the ECG appears to be normal, heart failure is unlikely.^1,5

Blood chemistry

Renal function, serum electrolytes, full blood count, thyroid function, blood glucose, liver function and fasting lipids should all be measured to detect any possible underlying causes of heart failure or alternative diagnoses^{1, 2}

Chest X-ray

Chest X-rays have long been used in the assessment of patients with suspected heart failure, but they are of limited sensitivity. The primary use of an X-ray should be to detect pulmonary oedema1 or identify other potential respiratory causes of breathlessness.

Oximetry

Monitoring peripheral oxygen saturation is particularly important in acute heart failure to prevent the development of hypoxaemia, which can be life-threatening.

Pulmonary function tests

Pulmonary function tests, such as spirometry and peak flow, can be used to assess the existence and severity of respiratory comorbidities.

Urinalysis

Urinalysis can used to rule out urinary tract infections and detect abnormal amounts of protein or glucose, which might indicate nephropathy or diabetes.

Classification

The severity of heart failure is classified using the New York Heart Association (NYHA) classification. This system grades the severity of symptoms and functional capacity of patients with heart failure.

Progression or regression through the four classes indicates deterioration of the condition or treatment effectiveness, respectively. A limitation of this classification system is its subjectivity; different patients have different views on what constitutes “ordinary” activity, as do the clinicians managing their care. Additionally, some individuals may reduce their activities subconsciously and consider this to be normal. Nevertheless, the NYHA classification remains the standard method of assessing heart failure severity.^1,2,5,8[10]

Prognosis

In most cases, the prognosis of patients with heart failure is poor. In 2010, NICE estimated that 30–40% of patients die within one year of being diagnosed, after which mortality drops to below 10% per year.² However, diagnostic and therapeutic options continue to evolve and are improving outcomes for this patient group.

There are many variables associated with poorer outcomes in heart failure and new prognostic indicators are proposed on a regular basis. The most commonly used indicators are age, NYHA class, persistent signs, comorbidities, increased hospital admissions and ischaemia-related heart failure. Other prognostic markers can be broadly placed in the following categories:¹

• Routine blood tests — eg, renal function (estimated glomerular filtration rate, creatinine clearance), serum sodium, haemoglobin
• Neurohormones and cytokines — eg, natriuretic peptides, plasma renin activity, galectin-3
• Electric variables — eg, QRS width, complex ventricular arrhythmias, heart rate variability
• Imaging variables — eg, ejection fraction, cardiothoracic ratio, fractional shortening
• Exercise testing — eg, peak oxygen consumption, six-minute walk distance

These markers are used together to enable clinical decision-making — particularly when considering advanced forms of treatment, such as device therapy or heart transplantation. 

Acknowledgement

Thanks to Helen Williams, consultant pharmacist for cardiovascular disease in South West London.