Heart murmurs

A heart murmur is an unusual or extra sound heard between the normal heartbeat sounds. A normal heartbeat makes 2 sounds – sometimes described as “lub-dub” – which are the sounds caused by the heart valves closing.

If you or your child has a heart murmur, there is often an extra whooshing, humming or swishing sound between the “lub” and the “dub” sounds.

Heart murmurs can be present from birth or may develop later in life. They can disappear over time or may be present throughout someone’s lifetime. In many cases, a heart murmur is harmless and does not signal any serious problems with the heart (often called an innocent heart murmur or a benign flow murmur). However, in other cases it can indicate a problem with the heart and requires further investigation.

What are the symptoms of a heart murmur?

Heart murmurs often cause no symptoms and you may not notice that you have one. A murmur is usually discovered during an examination when the doctor listens to your heart with a stethoscope.

An innocent heart murmur doesn’t cause any symptoms. However, if the heart murmur is abnormal you may notice associated symptoms, including:

  • Shortness of breath (this may be with heavy exercise, mild exercise or at rest, depending on severity)
  • Feeling light-headed or dizzy
  • Blackouts
  • Rapid heart rate or heart palpitations
  • Chest pain
  • Fatigue
  • Swelling of the feet and or legs
  • Bluish tinge on the skin around the lips or under the fingernails
  • Difficulty doing normal daily activities.

If you or your child have any of these symptoms it is important to see your doctor.

What causes a heart murmur?

An innocent heart murmur may be heard because the blood flows more rapidly than normal through the heart, or there is turbulence or a vibration in the blood as it travels through the heart. Sometimes it happens in people whose heart is closer to the front of the chest so extra sounds can be heard more easily. Things that may cause the blood to move more quickly through the heart are physical activity, fever, pregnancy, rapid growth of the body (e.g. during adolescence) and having certain medical conditions (e.g. hyperthyroidism or anaemia). Because young children have much faster heart rates than adults, many of them will have one of these harmless murmurs.

Abnormal heart murmurs may be caused by turbulent blood flow caused by structural problems in the heart itself. For example, some babies are born with a heart problem (known as a congenital heart defect). These can include:

  • Heart valve problems: The heart’s 4 valves control the movement of blood from one part of the heart to another. With each heartbeat, the valves open and close to keep the blood flowing smoothly and in the right direction. Sometimes the valves don’t close properly (known as regurgitation) and can leak, allowing blood to seep backwards from where it came from. In other cases, the valves may be too narrow (known as stenosis) so they don’t allow enough blood to move through the heart. Sometimes a heart valve problem may not be discovered until a person is older, even though they are present at birth.
  • Hole in the heart: Some babies are born with a hole in the wall that separates the 2 sides of the heart (called the septum).

Older children and adults can also develop heart murmurs. Sometimes a heart valve problem develops later in life, often due to infections (e.g. endocarditis, an infection of the inner lining of the heart and valves) or other medical conditions such as rheumatic fever, anaemia, hyperthyroidism or diseases of the heart muscle itself. An older person may also develop hardening or thickening of the valves, making it harder for blood to move through the heart.

Who is at risk of developing a heart murmur?

There is a higher chance of developing a heart murmur if you or your child:

  • Have a family history of heart murmurs
  • Have certain medical conditions such as chromosomal abnormalities (Down’s syndrome) hyperthyroidism, endocarditis (infection of the heart’s lining), some autoimmune diseases such as lupus (SLE) or rheumatoid arthritis, a past history of rheumatic fever or uncontrolled high blood pressure.

Women who develop rubella (German measles) or uncontrolled diabetes during pregnancy are also more likely to have a baby with a heart murmur.

Should I be worried if my child has a heart murmur?

Heart murmurs can be a cause of great anxiety, particularly if your child has one. However, most heart murmurs are innocent and do not mean that there is an underlying heart problem. Innocent heart murmurs often disappear by the time a child is a teenager.

If the doctor is not sure if the murmur is innocent, they will investigate further or refer you to a specialist. If there is an abnormality in the heart that is causing the murmur, treatment is usually possible.

How is a heart murmur diagnosed?

A heart murmur is usually discovered during an examination when the doctor listens to your heart with a stethoscope. To check whether the murmur is innocent or abnormal, the doctor will take note of how loud the murmur is, in what phase of the heartbeat it occurs, the pitch of the sound, whether the sound can also be heard in the neck or back and whether the sound changes when you change position. If the doctor suspects it is an abnormal heart murmur, further testing will be required. Tests may include:

  • Electrocardiogram (ECG): records the heart’s electrical activity
  • Echocardiogram: a type of ultrasound scan of the heart
  • Chest X-ray: to check if the heart is bigger than normal
  • Cardiac catheterisation: dye is injected into the heart to show any abnormalities
  • Cardiac MRI: a scan to examine the structure of the heart
  • Blood tests.

How is a heart murmur treated?

Innocent or harmless murmurs generally do not require treatment because they are not caused by a heart abnormality. If they are caused by another medical condition, treating that condition should get rid of the heart murmur. If your child has a fever when the heart murmur is found, the doctor will often want to see the child again once the temperature has returned to normal. This can also help to see if the murmur is innocent.

An abnormal heart murmur can indicate an underlying problem that needs to be treated. Treatment may include medicines and/or surgery, depending on how severe the problem is.

Surgery

Can be done to repair a hole in the heart or to repair or replace heart valves. Some procedures can be done via a catheter rather than open heart surgery.

Medication

There are no medicines that can cure heart valve disease, but they can help to manage associated problems. Depending on the underlying problems, medicines may be given to:

  • Slow the heart rate (e.g. beta blockers)
  • Treat infections (e.g. antibiotics to treat endocarditis)
  • Prevent blood clots (e.g. anticoagulants)
  • Reduce any excess fluid in the body (e.g. diuretics)
  • Lower blood pressure (e.g. ACE inhibitors)
  • Lower cholesterol (e.g. statins)

Can a heart murmur be prevented?

Heart murmurs can not usually be prevented. However, most murmurs are innocent (harmless) and do not cause any health problems. In people who have an abnormal heart murmur, treatments are available to manage the underlying cause. People who have heart murmurs due to valve problems may be more at risk of developing infections on their valves (endocarditis) during certain medical or dental procedures where there is a risk of bacteria entering the bloodstream. Discuss with your doctor if there is any need for you to have preventative antibiotics before such procedures.

References

1. Royal Children’s Hospital, Melbourne. Innocent murmur. http://www.rch.org.au/cardiology/parent_info/Innocent_Murmur/ (Accessed July 2016)
2. National Heart, Lung, and Blood Institute. Heart murmur. Updated Sept 2012. http://www.nhlbi.nih.gov/health/health-topics/topics/heartmurmur (Accessed July 2016).
3. Mayo Clinic. Heart murmurs. Updated April 2015. http://www.mayoclinic.org/diseases-conditions/heart-murmurs/basics/definition/con-20028706 (Accessed July 2016).
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