Heart murmurs (innocent)

A heart murmur is an extra or unusual sound made by the heart. It is usually the sound of the blood negotiating its way around the tight bends inside a young child’s heart and resembles a “whooshing” or “swishing” noise.

Heart murmurs are very common in babies and young children. In the vast majority of cases the heart is working normally and there 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, a heart murmur can be linked to a problem with the way that blood flows through the heart, or a structural problem with the heart. Even if an underlying problem is the reason for a baby’s heart murmur, there is treatment available. A heart murmur very rarely proves fatal.

Young children have small, slim chests so their hearts are nearer to a stethoscope than those of teenagers and adults, and their heart rate is faster.

Blood has to negotiate two tight bends as it flows through the heart. The flow of blood travelling through the heart and blood vessels in this way can also make a noise, and this is known as an ‘innocent’ murmur. Innocent murmurs can sometimes come and go, becoming noisier if the heart is beating fast - after exercise or with a fever - and quieter as a child sleeps.

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.

In rarer cases, 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 main arteries of the heart.

There are no outward signs or symptoms of an innocent heart murmur. Its presence is usually only detected during a routine doctor’s examination.

A doctor can hear normal heart valves closing and producing regular heart sounds by listening to the heart with a stethoscope. In this way, the doctor will be able to detect the presence of a heart murmur.

Some murmurs are clearly ‘innocent’ when heard through a stethoscope. If the murmur is innocent, no follow-up or treatment is needed.

If the quality of the murmur suggests that it might be due to some sort of structural oddity, the cause of the murmur needs to be established. Even then, most murmurs are not signs of a serious heart problem in children with no other symptoms.

A child might be referred to a heart specialist for a thorough examination and possibly further investigations. For instance an echocardiogram (an ultrasound scan of the heart) might be recommended.

This scan is designed to show the structure, function and blood flow of the heart, and will aim to rule out any underlying problem.

In most cases, an innocent murmur disappears as a child gets older and the bends within the heart become less tight.