What are the stages of heart failure?

The A to D staging system, long used in American guidance, looks at the whole course of heart failure, including the years before symptoms start. Stage A means you are at risk of heart failure but have no symptoms and no structural heart disease. Risk factors include high blood pressure, diabetes, coronary artery disease, obesity and a family history of heart muscle disease. At this stage, the focus is on controlling those risk factors.

Stage B, sometimes called pre-heart failure, means there are no symptoms yet, but tests show a change in the heart, such as a thickened heart muscle, damage from a previous heart attack, valve disease or reduced pumping function on an echocardiogram. Stage C means heart failure with current or previous symptoms, such as breathlessness, tiredness or ankle swelling. Stage D is advanced heart failure, where symptoms interfere with daily life or lead to repeated hospital admissions despite treatment.

Strictly speaking, stages A and B are not yet heart failure. In the UK, NICE uses the term heart failure only once symptoms are present, which is why the early stages are about recognising risk and preventing the condition from progressing.

The New York Heart Association (NYHA) classification describes how much your symptoms limit physical activity. It is not the same as the A-D stages; the stages describe the disease, while the NYHA class describes your current functional capacity. Your class can change as your condition stabilises or worsens.

Class I: ordinary physical activity does not cause undue breathlessness, fatigue, or palpitations. Class II: ordinary activity causes symptoms and slightly limits you. Class III: less than ordinary activity causes symptoms and markedly limits you. Class IV: symptoms occur at rest, and any physical activity increases discomfort. Your cardiologist may ask about everyday tasks, such as walking on the flat or climbing stairs, to gauge your class.

On 28 August 2026 the European Society of Cardiology published new guidelines on heart failure in the European Heart Journal. As well as adopting the A to D stages, they simplify how heart failure is grouped by ejection fraction, the percentage of blood the main pumping chamber pushes out with each heartbeat. The previous middle category, heart failure with mildly reduced ejection fraction (41 to 49%), has been removed. Heart failure is now described as either reduced ejection fraction (below 50%) or preserved ejection fraction (50% or more).

The guidelines also replace the term 'acute' heart failure with 'decompensated' heart failure, because in some people the heart does not suddenly get worse but gradually loses its ability to compensate. Medicines are now grouped as foundational therapy, which has the strongest evidence, additional therapy for particular groups of patients, and interventional treatments such as devices and procedures.

European guidelines do not automatically change NHS care. In England, heart failure is managed according to NICE guidance, which still uses three ejection fraction groups: reduced (40% or less), mildly reduced (41 to 49%) and preserved (50% or more). If you already have a diagnosis, your treatment will not change simply because the terminology has, but you may come across the new terms in letters or reports.

If heart failure is suspected, the first steps are usually a detailed history, an examination and a blood test for a natriuretic peptide called NT-proBNP, which rises when the heart is under strain. NICE recommends that people with a very high level (above 2,000 ng/L) see a specialist and have an echocardiogram within two weeks, and those with a raised level (400 to 2,000 ng/L) within six weeks. A level below 400 ng/L makes heart failure less likely, although it does not rule it out completely.

An echocardiogram is the key test. It shows how well the heart is pumping, measures the ejection fraction, and shows whether the heart muscle is thickened or stiff or whether a valve is causing the problem. Other tests may include an electrocardiogram (ECG), a chest X-ray and, in some cases, a cardiac MRI scan for detailed pictures of the heart muscle. If palpitations or an irregular heartbeat are part of the picture, Holter monitoring can record your heart rhythm over a longer period.

Treatment depends on the type and stage of heart failure. For heart failure with reduced ejection fraction, NICE recommends a combination of four medicines (an ACE inhibitor, a beta-blocker, a mineralocorticoid receptor antagonist and an SGLT2 inhibitor), alongside lifestyle changes and cardiac rehabilitation. Ongoing care is usually shared between your GP and a specialist heart failure team, who adjust medicines over time.

This article draws on the 2026 European Society of Cardiology Guidelines on heart failure, the National Institute for Health and Care Excellence (NICE) guideline on chronic heart failure in adults, and NHS information on heart failure. For personalised advice, please speak to your GP or a consultant cardiologist.

Please remember that this is general information and not a substitute for individual medical advice. Call 999 if you have severe difficulty breathing, chest pain that could be a heart attack, or you collapse. If you become breathless when lying down or during everyday activities, notice new swelling in your ankles or legs, or gain weight suddenly, contact your GP urgently or call NHS 111.