Heart Murmur

What Is a Heart Murmur?

A heart murmur involves an abnormal sound which is heard when a doctor listens to your heartbeat. Murmurs can be faint or loud and at times they may sound like a swishing noise. The ‘lub-dub’ sound heard when you listen to your heartbeat is caused by the heart valves closing and is completely normal.

A heart murmur is not a medical condition or disease, but is instead a noise that can be heard by a doctor when they listen to your heart beating through a stethoscope. In most cases heart murmurs are completely harmless. However, they can be a symptom or sign of something wrong with the heart and should be investigated, especially if the patient has additional symptoms.

Types of heart murmur

Heart murmurs are usually classified into two categories: innocent and abnormal.

Innocent heart murmurs

This type of murmur is also known as a harmless heart murmur. Individuals with this type of heart murmur usually have no other symptoms or signs of heart problems. Innocent heart murmurs are most common among healthy children.

Abnormal heart murmurs

People who have abnormal heart murmurs usually have other symptoms or signs of heart problems. In children they are usually caused by congenital defects (they are there at birth). In adults, however, unusual heart murmurs are usually caused by problems relating to the heart valves, which may be caused by infection, ageing or disease.

The workings of the Heart

Your heart is a large muscle and is roughly the same size as your fist. Its primary role is to pump blood around the body to provide tissues and organs with oxygen. The heart pumps around 100,000 times each day.

The heart is made up of two sides and they are separated by the septum, which acts like a wall between the two sides. The right section of the heart drives blood towards the lungs to collect oxygen, while the left hand section pumps blood around the remainder of the body. The blood rich in oxygen then flows to the left hand part of the heart and is taken to the remainder of the body in the bloodstream.

The heart is comprised of four valves and four chambers and is connected to veins and arteries (types of blood vessel). Arteries take blood from the heart and distribute it around the remainder of the body, while veins transport blood from the body towards the heart.

Heart chambers

The heart is made up of four chambers, which are known as:

  • Atria (plural of atrium): these chambers are located in the heart’s upper section and collect blood on arrival in the heart.
  • Ventricles: these chambers are located at the bottom of the heart. They are responsible for pumping blood from the heart towards the remainder of the body.

Heart valves

The heart contains four valves which are responsible for allowing the passage of blood and preventing backflow. The valves open and shut like doors and it is this action which causes the ‘lub-dub’ sound you hear when listening to the heart beating. The initial sound is caused by the closing of mitral valves and tricuspid, when the heart constricts and forces blood out and into the body (this is known as systole), and the next sound is caused by the closing of the pulmonary and aortic valves, when the heart settles slightly to fill with blood (this is known as diastole).

The valves include:

  • Tricuspid valve: the tricuspid valve is located on the right section of the heart, based between the right ventricle and the right atrium.
  • Pulmonary valve: located on the right hand section of the heart, found between the pulmonary artery and the right ventricle. The responsibility of the pulmonary artery is to carry blood from the heart towards the lungs.
  • Mitral valve: the mitral valve is based on the left hand section of the heart, found between the left ventricle and the left atrium.
  • Aortic valve: this is located on the left hand side of the heart and is situated between the aorta and the left ventricle. The aorta artery is responsible for transporting blood from the heart to the remainder of the body.


The arteries are major blood vessels which are joined to the heart and are responsible for carrying blood towards the remainder of the body. Major arteries include:

  • Pulmonary artery: the pulmonary artery transports blood from the right hand section of the heart towards the lungs to collect oxygen.
  • Aorta: the aorta is a major artery that transports blood rich in oxygen from the left hand section of the heart towards the remainder of the body.
  • Coronary arteries: the coronary arteries transport oxygenated blood from the aorta towards the muscle tissue of the heart. It is essential for the heart to have its own supply of oxygen to be able to function properly.


The veins are major blood vessels which are connected to the heart and are responsible for carrying blood to the heart. Major veins include:

  • Pulmonary vein: the pulmonary vein carries blood rich in oxygen found in the lungs towards the heart. This vein is connected to the left hand section of the heart.
  • Vena cava: the vena cava is a large vein and is responsible for carrying blood back towards the heart from the remainder of the body.

Other names for a heart murmur

Innocent heart murmur:

  • Normal heart murmur.
  • Benign heart murmur.
  • Physiologic heart murmur.
  • Functional heart murmur.
  • Flow murmur.
  • Still’s murmur.

Abnormal heart murmur:

  • Pathologic heart murmur.

What are the main causes of heart murmurs?

Innocent heart murmurs

Innocent heart murmurs occur when the blood travels in the course of the heart loudly. This may be caused by the blood travelling through the blood vessels and heart quicker than average or by a larger amount of blood running in the course of the heart. Certain conditions can cause the blood to travel in the course of the heart quicker than average, including:

  • Anaemia.
  • Fever (a high temperature).
  • Hyperthyroidism (an overactive thyroid gland, which causes levels of the thyroid hormone to be elevated).

Heart murmurs are very common in children. Pregnancy is also a common source of fast flowing blood. Many females acquire an innocent heart murmur at times of pregnancy, because the body is producing additional blood for the developing foetus. In some cases innocent heart murmurs can develop following heart surgery or as a consequence of getting older.

Abnormal heart murmurs

The most common reason for abnormal heart murmurs are congenital heart defects. These are defects which affect the development of the heart or vessels around the heart and are present at birth. A number of babies have one defect or more. Examples of defects that may lead to abnormal heart murmurs include:

  • Congenital septal defects: these defects cause holes within the septum (the wall separating the two parts of the heart). Septal defects account for over half of abnormal heart murmurs in children.
  • Congenital valve defects: these include narrow and leaking valves, which prevent blood from travelling in the course of the heart normally.

Other health conditions and infections can cause heart murmurs, including:

  • Endocarditis: this occurs when the inside of the heart lining and heart valves become inflamed and is most often the result of a bacterial infection. Endocarditis is classed as a serious condition, which can cause permanent or long lasting injury to the heart and other health complications. Endocarditis is most common among people who already have heart problems.
  • Rheumatic fever: this is a serious illness and can occur after scarlet fever or strep throat infection. Rheumatic fever can cause lasting harm to the heart. It is important that patients who are diagnosed with scarlet fever or strep throat follow treatment advice carefully and complete courses of antibiotics to prevent the development of rheumatic fever.
  • Calcification: this condition causes the heart valves to become solid and thick, impairing their function. Calcification is often caused by ageing.

What are the symptoms and signs of heart murmurs?

The majority of people with heart murmurs do not display any symptoms or signs of heart difficulties and the only symptom they have is the loud noise the heart makes when it beats. Heart murmurs are often innocent, meaning that they are harmless, but this is not always the case and some people do develop symptoms. Possible symptoms associated with a heart murmur include:

  • Poor eating habits and delayed development in children.
  • Chest pain.
  • Fainting.
  • Dizziness
  • Difficulty catching your breath.
  • Feeling tired.
  • Blue discolouration of the skin (usually the inside of the mouth and the hands).
  • Rapid breathing.
  • Sweating.

The severity and type of symptoms will depend on the source of the murmur.

How can a heart murmur be diagnosed?

Doctors assess the beating heart using an instrument known as a stethoscope. When they monitor the heart beating they can identify the murmurs. Innocent heart murmurs are often identified during routine physical examinations or health checks. It is also possible for doctors to pick up signs of an abnormal heart murmur during a routine examination, but most abnormal murmurs are caused by congenital conditions and diagnosed at birth.

If a doctor suspects an abnormal heart murmur it is likely that they will refer the patient to a heart specialist (known as a cardiologist) for further tests.

Physical examination

During a physical examination a doctor will listen to the patient’s heart using a stethoscope. They will listen to the heartbeat carefully to detect any murmurs and try to decide whether a murmur is abnormal or innocent. They do this by listening to the sound and evaluating how loud it is, how long it lasts and where it is coming from.

The doctor will also take a medical history, family history (to see if there is a history of heart problems) and ask the patient whether they are experiencing any symptoms. They will also look for signs of heart problems, such as rapid breathing, blue discolouration of the hands and mouth, dizziness and chest pain during an examination.

Evaluation of murmurs

When listening to the heart and assessing a murmur, doctors will consider the following things:

  • The volume of the sound.
  • The timing of the sound (when it occurs in the heartbeat cycle).
  • The location of the sound.
  • If the sound can be noticed in the chest, and whether it is also heard in the back or neck.
  • The length of the sound.
  • How the sound is affected by changing position, doing exercise or breathing deeply.

Classification of murmurs

Murmurs are classified as follows:

  • Systolic: this is the sound heard when listening to the heart squeezing to push blood out and around the body.
  • Diastolic: this sound can be noticed when the heart settles or relaxes to fill with blood. Diastolic murmurs are commonly symptomatic of defects or heart problems and should be investigated further.
  • Continuous: this sound can be heard continuously throughout the heartbeat and is often the sign of heart disease or a heart defect, which should be investigated further. 


If a doctor suspects that a patient has an irregular heart murmur they will order further tests, which may include:

  • Chest X-ray: an X-ray can reveal whether the heart is engorged and highlight problems with the lungs and the heart.
  • ECG (electrocardiogram): an ECG is a test used to calculate heart rate and the regularity of the heartbeat. The ECG can help to rule out certain heart problems.

Once a patient has been referred to a specialist cardiologist further tests will be carried out, including:

  • Echocardiogram (known as an echo): this test uses ultrasound waves to show the heart in detail as it squeezes and then settles. The echocardiogram offers greater detail than an X-ray and shows doctors how the heart is functioning. In some cases a transoesophageal echocardiogram may be required, as this gives a more detailed image of the heart. The procedure involves inserting an ultrasound probe through the throat and into the oesophagus, which is carried out under sedation.
  • Angiography and cardiac catheterisation: angiography requires the injection of a coloured dye to enable doctors to see the passage of blood travelling through the blood vessels and heart more clearly. Cardiac catheterisation involves inserting a catheter through a vein or artery in the leg or arm to arrive at the heart, in order to measure the pressure found inside the surrounding blood vessels and the heart.

How do you treat heart murmurs?

Innocent heart murmurs

Innocent heart murmurs do not usually require any treatment. Children with innocent heart murmurs have healthy hearts and do not require treatment, and the same is true for pregnant women. However, it is worth mentioning the heart murmur when you have health checks to ensure the doctor is aware of the murmur and can monitor the situation. If the murmur is caused by a condition or infection, such as anaemia or fever, treating the cause will often cure the murmur.

Abnormal heart murmurs

Treatment is based on the severity and reason for the murmur, with treatments likely to include medication and surgery. Children with congenital heart defects will be treated by paediatric cardiologists.

Key facts about heart murmurs

  • A heart murmur involves an abnormal sound that can be heard when a doctor listens to the heartbeat using a stethoscope. Murmurs can be faint or loud like a whooshing sound.
  • The majority of heart murmurs are innocent, meaning that they are harmless.
  • In some cases a heart murmur may indicate heart conditions, particularly if the individual has other symptoms and signs.
  • Innocent heart murmurs are a common occurrence in healthy children and do not mean that the heart is abnormal or damaged in any way.
  • Doctors will listen to the heartbeat using a stethoscope to determine whether a murmur is abnormal or innocent.
  • Doctors listen out for the location, loudness and timing of the sound to help them diagnose an innocent or abnormal murmur.
  • The most common reason for an abnormal heart murmur in children is congenital heart defects (develop during pregnancy and are present at birth).
  • The most common source of abnormal heart murmurs in adults are disorders of the valves caused by infection, ageing and disease.
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