Heart murmurs are very common, especially in young children. In the vast majority of cases, the heart is working normally and a murmur isn’t anything to worry about. In fact many young children have heart murmurs and neither they nor their parents will ever know anything about it. Occasionally though it can be linked to a problem with the way that blood flows through the heart, or a structural problem within the heart.

What causes a heart murmur and who can get it?

Young children have small, slim hearts compared to those of teenagers and adults and their heart rate is also faster. They are also more likely to have a heart murmur. In most cases this is known as an ‘innocent’ murmur. This happens because the blood has to negotiate two tight bends as it flows through the heart.

As blood enters the heart, it comes into a filling chamber then drops through a valve into the right pump chamber. From there, it’s pumped upwards towards the lung artery, negotiating a U-bend in the process. The blood then flows through the lungs. It returns to the left side of the heart into a top filling chamber, drops into a bottom left pump chamber and is then pumped upwards into the artery leading to the body, negotiating a second U-bend.

In young children, with small hearts, these bends are relatively tight and many of the murmurs heard in young children are in fact blood flow noises as the blood is pumped through these tight bends of the heart.

More rarely though a heart murmur can come from abnormal blood flow within the heart and blood vessels. This might be related to either a narrow or leaking valve, or a hole in the wall between the two chambers of the heart or between the two arteries.

How is it normally diagnosed and treated?

By listening to the heart with a stethoscope, a doctor can hear the heart valves closing and producing normal, regular heart sounds. The flow of blood travelling through the heart and blood vessels can also make a noise, and this sound is termed a murmur.

If the murmur is innocent, no follow-up or treatment is needed.

If a more complex problem is suspected, occasional follow-up may be needed along with advice with regard to the risks of infection. A child might also be referred to a heart specialist for a thorough examination.

Looking forward

As the years go by, the heart rate slows and the heart grows and lies deeper within the body. The normal bends within the heart become less tight, and an innocent murmur therefore disappears.

Follow-up may be needed if the murmur is related to a more complex problem.

For more help and information

If you would like to know more about heart murmurs, please ask your doctor.

Last reviewed by Great Ormond Street Hospital: 26 February 2007

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