What to know about heart murmurs
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?
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.
Learn more about flow murmurs here.
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
- 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.
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
- Marfan syndrome
- Noonan syndrome
- systemic lupus erythematosus
- congenital rubella syndrome
- rheumatic fever
- Ebstein’s anomaly
- mitral valve prolapse
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
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
- bluish skin
- chronic cough
- swelling in the legs or abdomen
A newborn baby may have:
- difficulty feeding
- stunted growth
- a bluish hue to the skin during feeding or activity
- breathing difficulties
- excessive fussiness
When to contact a doctor
Doctors usually diagnose heart murmurs during a routine physical exam. Heart murmurs may not be serious, but a person should always check them with a doctor to exclude something serious, even if there are no symptoms.
A person should contact a doctor if they regularly:
- feel faint or lightheaded
- have shortness of breath
- have swelling in the legs and ankles due to fluid building up
Doctors will listen to the heart with a stethoscope and check for abnormal breathing patterns and any changes in skin color.
They may need to run other tests for heart function, including measuring blood pressure, the amount of oxygen in the blood, and pulse rate. Doctors will also usually use an echocardiogram to take pictures of the heart valves.
They will then provide a grade or scoring for every heart murmur. The grading system for murmurs that occur when the heart is squeezing is 1–6, where 1 is very faint, and 6 is very loud. For murmurs that occur when the heart relaxes, the grading system is 1 to 4.
It is important to note that the volume of the murmur does not correlate with its severity. A softer murmur may sometimes mean the condition is more severe.
Doctors also need to determine the duration of the heart murmur and its exact location in the heart.
For a closer examination, doctors may order the following tests:
- cardiac catheterization
- chest X-ray
- stress echocardiogram
These tests help doctors determine the cause of the heart murmur, its intensity, its severity, and whether or not it is causing symptoms.
Heart murmurs themselves may not typically require treatment.
However, abnormal heart murmurs are a symptom of an underlying condition that may require treatment.
Doctors will recommend treatments that reduce blood pressure to improve blood flow across the valve, reduce damage to the valve, or both. For example, people may require medications including:
- ACE inhibitors
- antiarrhythmic medications
- beta-blockers or calcium channel blockers
- water pills
Doctors may prescribe single medications or a combination of several.
Some people will require surgery to repair or replace a defective valve. However, people with mild heart valve disease may never require surgery.
That said, if the heart valve defect begins to affect blood flow through the heart significantly, cause symptoms, or increase pressure in the heart, a valve repair or replacement might be necessary.
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.
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.