Innocent heart murmurs are small, unusual noises that occur when listening to the heart. If your child's murmur has been diagnosed as "innocent", this means that the murmur is harmless and is not a sign of a heart problem. 

It occurs when the blood flows through the large veins of the heart, or the flow of blood around the bends of the heart. Children’s hearts are compact so the bends of the heart are quite tight, which means their heart rates are faster than adults. This causes the normal flow of blood to create a soft noise or murmur, which can be compared to the noise that water makes in a stream as it curves around a bend.

These noises are sometimes called:

  • vibratory murmurs
  • venous hums
  • functional murmurs.

These murmurs are often heard at a routine examination or when there is an infection. Innocent murmurs are louder when the heart is beating faster than usual, such as when your child has a temperature or is particularly worried.

Innocent heart murmurs come and go. They also vary with breathing, with the heart rate and with the position of the child.

What happens if my child has an innocent heart murmur?

Innocent heart murmurs eventually disappear as a child grows older and his or her heart grows bigger. This means no special precautions or follow ups are needed.

Read our information leaflet on what it means when we say your baby has an innocent heart murmur.

Innocent heart murmur - August 2020 (PDF, 356KB)