A heart murmur is an abnormal sound the blood makes as it moves through the heart. Murmurs can be benign or indicate a serious heart condition.

Research estimates that heart murmurs affect up to 72% of children. Often, the murmur will go away with age. However, some people may live with a heart murmur into adulthood.

In adults, some heart diseases — including heart valve disease — can cause heart murmurs.

In this article, we describe the types of heart murmurs, their causes, and some treatment options.

What is a heart murmur?

A doctor may check for a heart murmur with a stethoscope.

Heart murmurs result from vibrations, or turbulence, that blood causes when it flows through the heart. It produces sounds that doctors can hear through a stethoscope.

When heart valves open and close, they make a “valve sound.” However, valves that do not open or close normally can cause blood to leak backward or prevent blood from flowing forward, creating a sound called a murmur.

Blood that moves very quickly through the heart can also create a type of murmur called a “flow murmur.”

There are two main types of heart murmur: innocent and abnormal. Flow murmurs are a type of innocent murmur.

Innocent or benign heart murmurs occur when no structural abnormality or heart condition is present. Abnormal heart murmurs, meanwhile, occur where an underlying heart condition is causing the symptom.

A person with a heart murmur should seek professional evaluation by a doctor to determine if their murmur is innocent or needs additional testing and monitoring.

Innocent heart murmur

Innocent heart murmurs, such as those due to a high blood flow, can disappear over time without the need for treatment. They are more common in children or adolescents.

Doctors do not usually consider innocent heart murmurs to be serious.

However, the murmur may be due to minor valve dysfunction, which health professionals will need to monitor without necessarily performing significant intervention.

Abnormal heart murmur

Abnormal heart murmurs indicate an underlying heart condition.

Abnormal heart murmurs in adults are usually associated with heart valve disease. They may have links with:

• valve calcification
• endocarditis
• rheumatic fever

Types of heart murmurs

Doctors classify heart murmurs by the stage of the heartbeat at which they hear the sound. They listen to the heart through a stethoscope. Valves in the heart open and close as it pumps, making a thumping sound. Doctors can then define the murmur in the following ways:

• Systolic murmur: The sound occurs when the heart muscle contracts.
• Diastolic murmur: The murmur happens as the heart muscle relaxes and blood enters the heart’s lower chambers.
• Continuous murmur: Doctors can hear the murmur throughout the heartbeat while the heart is pumping and relaxing.

Causes

There are many possible causes of heart murmurs.

Doctors categorize murmurs according to what causes them:

• Flow murmurs: Exercise, pregnancy, and anemia can all cause a high blood flow, as can hyperthyroidism, fever, and rapid growth spurts. High blood flow could lead to an innocent murmur.
• Valve disease-related murmurs: Problems with a valve in the heart, such as aortic stenosis or a bicuspid aortic valve, can lead to a heart murmur.
• Murmurs due to ventricular problems: Conditions that affect the ventricles and the blood flow through them, such as functional mitral regurgitation, may cause a murmur.
• Murmurs due to complications of other conditions: Some conditions that affect the heart, such as endocarditis and lupus, may also cause a heart murmur.
• Murmurs related to congenital heart disease: Problems with the heart present from birth, such as a hole in the heart, can result in a murmur.

Specific conditions and factors that can cause abnormal heart murmurs

Abnormal heart murmurs may happen due to various factors, including:

• Heart valve disease: This is the result of a defect in the heart’s structure. Some of these conditions can be present at birth or acquired.
• Patent ductus arteriosus: This occurs when the opening between the aorta and pulmonary artery does not close after birth, as it should.
• Age: Calcium can build up in the heart valves with age. This reduces the opening of the valves, making it harder for blood to pass through them.
• Aortic valve defects: Sometimes, the aortic valve becomes dilated or stretched and stops working properly. This causes blood to leak backward, producing a heart murmur. Doctors call this condition aortic regurgitation.
• Infective endocarditis: This is a bacterial infection of the heart’s lining, which can also affect the valves. The growth of bacteria will narrow the opening of the valves and affect blood flow through them.
• Chronic rheumatic heart disease: People with this condition have chronic inflammation in the heart valves, which affects the function of the valves and, therefore, the blood flow through those valves.
• Tumors: Tumors can also form on a heart valve. Tumors in other parts of the heart, such as the left atrium, can cause a heart murmur by affecting the blood flow through the heart.
• Septal defects: Arterial and ventricular septal defects mean there are holes in the walls between the upper or lower chambers, respectively.

Other conditions that can cause heart murmurs include:

• degenerative valve disease
• left ventricular outflow tract obstruction
• hypertrophic obstructive cardiomyopathy
• Turner’s syndrome
• Ehlers–Danlos syndrome
• mitral valve prolapse

Location

Heart defects can affect the following parts of the heart:

• the aortic valve, which can be bicuspid, with only two leaflets, instead of tricuspid, with three leaflets
• the pulmonary valve
• the atrial septum, which separates the atria
• the ventricular septum, which separates the ventricles

Symptoms

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A person with an abnormal heart murmur may experience dizziness.

People with heart murmurs may not experience any symptoms.

Others, specifically those with abnormal heart murmurs, may experience symptoms depending on the underlying cause.

For example, people can experience:

• shortness of breath
• dizziness
• fainting
• bluish skin
• chronic cough

Outlook

Innocent heart murmurs are benign and do not usually require medical attention. Abnormal heart murmurs, however, signal an underlying heart condition.

When treating abnormal heart murmurs, the doctor must first determine the cause. Sometimes, people need surgery to repair a defective valve. Others may not need surgery and will be able to lead a relatively healthy life.

Heart valve disease is more common with age. Doctors can help people manage heart murmurs and improve the function of the heart.

Summary

Heart murmurs describe an abnormal sound when the heart is beating. Doctors name heart murmurs depending on when in a heartbeat the sound is loudest. Innocent heart murmurs are benign, while abnormal heart murmurs may indicate an underlying condition.

Many children with heart murmurs do not need treatment, as the condition can improve as they age. However, in adults, a heart murmur may be a symptom of another disease. Doctors will order tests to determine the cause of the murmur and may prescribe medication to treat the underlying condition.

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