Heart murmurs: what they are, causes, symptoms and when they matter

The BHF explains that a heart murmur is an extra, unusual sound in your heartbeat, sometimes described as a whooshing or swishing noise. It can be heard when a doctor listens to your heartbeat through a stethoscope. The extra noise happens when blood does not flow smoothly through your heart.

The NHS says heart valve disease is sometimes found by chance when a doctor hears an unusual sound, a heart murmur, while listening to your chest. A murmur is therefore a finding, not a diagnosis in itself.

The BHF classes murmurs as innocent or abnormal. An innocent heart murmur is where the heart still beats normally but makes extra sounds when blood flows through it faster than usual. Innocent murmurs are harmless, common in babies, young people and adults, and can come and go or happen regularly throughout life.

An abnormal heart murmur is where the extra sounds are caused by a problem with the heart. This can be dangerous if left untreated, but the BHF says this is not common and is rare in babies and young people.

The BHF says many people with a heart murmur do not feel any symptoms. Depending on what is causing it, you may have symptoms like those below. If you have symptoms, visit your GP, who can listen to your heart with a stethoscope and refer you for tests or specialist treatment if needed.

• Fainting or dizziness.

• Chest pain.

• Shortness of breath.

• Swelling in the legs, arms or tummy area.

• A continuous cough that does not seem to be getting better.

• Sweating a lot when resting or doing minimal activity.

• Lack of appetite (in babies and children only).

The BHF says you should call 999 immediately if you are experiencing pain in your chest or upper body, or difficulty breathing or shortness of breath. The NHS says to call 999 or go to A&E if you are struggling to breathe, have sudden chest pain that spreads to your arms, back, neck or jaw or lasts more than 15 minutes, or have chest pain with shortness of breath or heart palpitations. It adds not to drive to A&E.

The NHS says to see a GP if you are short of breath regularly, feel tired, weak or dizzy during normal activities, have palpitations that keep coming back or are getting worse, have swollen ankles or feet, or have chest pain that comes and goes. These can have many causes, but should be checked.

The BHF says innocent murmurs can be heard when blood flows through the heart faster than usual. This can be caused by an overactive thyroid, sudden growth in babies and young people, exercise that raises the heart rate, pregnancy (because the body pumps extra blood), having a fever, or anaemia.

Abnormal murmurs are caused by a problem with the heart, which the BHF says can be an infection (sometimes bacteria infecting the heart muscle, leading to conditions like rheumatic fever), a congenital heart condition (structural problems that develop in the womb) or heart valve disease (a problem with the valves interrupting normal blood flow).

The BHF says there are three main types, based on when they happen during the heartbeat. Each type can sound different and may point to different causes. The doctor decides after listening to your heart whether further tests are needed.

The BHF says it is common for babies and children to have innocent heart murmurs. They usually disappear by puberty, between the ages of 8 and 14, and do not need any treatment. A child's harmless murmur may come and go depending on their breathing, heart rate and how active they are. Abnormal murmurs are rare in babies and young people.

The NHS lists congenital heart disease, where a person is born with the condition, as one cause of heart valve disease. Ask the GP or your child's doctor to arrange tests if your child has symptoms such as breathlessness, poor feeding or tiredness, since the BHF lists a lack of appetite in babies and children as a possible symptom.

The BHF says pregnancy can cause an innocent murmur because the body makes and pumps extra blood for the baby. The NHS says it is important to get advice from a heart specialist if you are pregnant or want to get pregnant and have heart valve disease, because pregnancy can make symptoms worse. You can usually have a safe pregnancy, but you may need extra monitoring and treatment.

The BHF says your doctor listens to your heart with a stethoscope. If they think it could be an abnormal heart murmur, your healthcare team may arrange tests to find the cause: a chest X-ray to see if the heart looks bigger than it should be, an ECG to check heart rhythm, rate and electrical activity, and an echocardiogram, an ultrasound of the heart to look at the structure of the heart and valves. The NHS lists the same three tests for suspected heart valve disease.

The BHF says innocent heart murmurs do not usually need treatment. If a murmur is caused by a problem with the heart or another condition, the cause may need treatment, and your doctor will discuss options. Treatments may also be recommended to manage symptoms even if there is no underlying heart condition.

For heart valve disease, the NHS says mild disease without symptoms may need no treatment but regular check-ups. People with symptoms or severe disease may need medicines (such as ACE inhibitors, diuretics, beta blockers or anticoagulants) and severe disease usually needs surgery to repair or replace the valve. The NHS lists complications of valve disease as heart failure, atrial fibrillation, stroke and endocarditis.

On the NHS, a murmur is usually picked up by a GP or midwife, and an echocardiogram is arranged if there is reason for concern. Cardiology clinics see people with abnormal murmurs. Private cardiology clinics can offer an earlier echocardiogram, but follow-up of valve disease is generally shared with NHS services, so ask for results to be sent to your GP.