A heart murmur is an abnormal sound that the blood makes as it moves through the heart. Doctors can hear a heart murmur through a stethoscope. Murmurs can be benign or indicate a serious heart condition.
Research estimates that heart murmurs affect up to 72% of children. Most often, the murmur will go away with age. However, some may live with a heart murmur into adulthood.
In adults, meanwhile, some heart diseases — including heart valve disease — can cause heart murmurs.
In this article, we describe the two types of heart murmur, their causes, and some treatment options.
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, which can create 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 can sometimes disappear over time without the need for treatment, such as if it is due to a high blood flow.
Other times, the murmur may be due to minor valve dysfunction, which health professionals can monitor without needing to suggest significant intervention.
People with innocent heart murmurs can live a relatively normal life. They can usually exercise and take part in sports without any problems.
Abnormal heart murmur
Abnormal heart murmurs indicate an underlying heart condition. These are less common than innocent heart murmurs and can either continue into adulthood or occur for the first time in adulthood.
Abnormal heart murmurs in adults are usually associated with heart valve disease.
There are many possible causes of heart murmurs.
People can 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. This 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 flow of blood 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 that are present from birth, such as a hole in the heart, can result in a murmur.
People with abnormal heart murmurs may have congenital heart disease or a heart valve disease.
Heart valve disease is the result of a defect in the heart's structure. Some of these conditions can be present at birth or acquired.
Heart defects can affect the following parts of the heart:
- the aortic valve, which can be bicuspid (two leaflets) instead of tricuspid (three leaflets)
- the pulmonary valve
- the atrial septum, which separates the atria
- the ventricular septum, which separates the ventricles
Another heart defect is a patent ductus arteriosus. This occurs when the opening between the aorta and pulmonary artery does not close after birth, as it should.
When heart valve defects occur in adults, heart murmurs can be the result of age, tumors, or infections. For example, 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.
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.
It is also possible to develop infective endocarditis. This is a bacterial infection of the lining of the heart, which can also affect the valves. The growth of bacteria will narrow the opening of the valves and affect blood flow through them.
Another condition that can affect the heart is 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 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.
Other conditions that can cause heart murmurs, include:
People with heart murmurs may not experience any symptoms.
Others, specifically 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
Doctors will listen to the heart with a stethoscope. They will also check for abnormal breathing patterns and any changes in skin color.
They may also need to run other tests for heart function, including measuring blood pressure, the amount of oxygen in the blood, and pulse rate. Also, doctors will usually use an echocardiogram to take pictures of the heart valves.
They will then provide a grade 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.
Doctors also need to determine the duration of the heart murmur and its exact location in the heart.
On rare occasions, the following procedures are also necessary:
- cardiac catheterization
- chest X-ray
- stress echocardiogram
These tests help doctors determine the cause of the heart murmur, as well as its intensity, its severity, and whether or not it is causing symptoms.
Heart murmurs are usually innocent. These do not typically require treatment or further testing.
Abnormal heart murmurs, however, 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 such as:
- ACE inhibitors
- anti-arrhythmic 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 a defective valve. However, some people with mild heart valve disease may never require surgery.
That said, if the heart valve defect begins to significantly affect blood flow through the heart, 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.