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Independents' Day

The asymptomatic child with a heart murmur

Paediatric cardiologists Dr Rodney Franklin and Dr Zdenek Slavik explain which murmurs are innocent and which are pathological

Paediatric cardiologists Dr Rodney Franklin and Dr Zdenek Slavik explain which murmurs are innocent and which are pathological

Heart murmur is the most frequent paediatric cardiology problem facing GPs. Up to 90% of children – if carefully screened – will be found to have a murmur at some point during their development.

No more than 1% of these children will have CHD – the others will have benign or innocent murmurs. The differential diagnosis is therefore between the following:

• a haemodynamically significant heart lesion requiring an intervention in the near future and early referral – usually the child will demonstrate other abnormal signs and, on closer questioning, symptoms that will dictate the urgency of the referral

• a more minor heart lesion, requiring regular reviews with the possibility of an intervention over the medium term such as a small ventricular septal defect (VSD) or semilunar valve stenosis, requiring elective referral

• an innocent murmur.

Managing parental expectations

Currently best practice dictates that a strong suspicion of any form of CHD requires assessment at an early stage by a paediatric cardiologist or a paediatrician with an interest in this area, who has the facility to perform an echocardiogram.

Unfortunately GPs find it increasingly difficult not to refer asymptomatic patients with clear-cut innocent murmurs. Parental expectations, based on media and internet-sourced information, create an environment in which only an echocardiogram will provide sufficient reassurance.

By the time the child reaches the paediatric cardiologist it is often more efficient and effective to perform an echocardiogram and provide parents with an information leaflet explaining the nature of such murmurs, than to explain why an echocardiogram is unnecessary on clinical grounds, particularly when they expect this investigation.

An ECG in such cases is often too insensitive to be used as an effective screening tool and a chest X-ray is certainly not justified.

Spotting an innocent murmur

When deciding that a murmur is innocent:

• the history must confirm a lack of symptoms and the examination must exclude heart failure and cyanosis

• peripheral pulses must be demonstrably normal and equal, with a quiet precordium

• heart sounds should be normal with a non-accentuated pulmonary component of the second heart sound, which moves normally with respiration (best heard when non-supine).

An ejection click or gallop rhythm will be absent.

Innocent murmurs are usually soft (I–II/VI intensity), are either systolic or continuous (never diastolic), vary with posture, are accentuated by coexistent fever, infection or anaemia, and tend to be localised.

Pathological murmurs are usually loud (above II/VI intensity), may be heard at any point in the cardiac cycle, may be accompanied by added sounds, and tend to have wide radiation, not varying with posture or respiration.

Stenotic semilunar valve murmurs will be apparent soon after birth, whereas septal defect-related murmurs may take months to become apparent. Innocent murmurs become less audible with age, as the chest wall thickness increases, but may still be audible in up to 20% of adolescents. Such murmurs may persist throughout life. They characteristically may be present at one examination but not at another.

There are five main types of innocent murmur that can usually be diagnosed with confidence rather than by exclusion.

1. Infantile pulmonary murmur

This occurs in the premature and in early infancy. It is caused by flow acceleration over the pulmonary bifurcation and is characterised by a soft ESM maximal at the upper left sternal border (LSB) with radiation into the axilla and even the back. It disappears before one year of age.

2. Still's murmur

This common innocent murmur, first described in 1909, is a low-pitched ESM, best audible in the mid to lower LSB, with radiation towards the apex and occasionally upper precordium.

It is described as being vibratory, musical, buzzing or ‘twangy' and is louder when supine, because of increased stroke volume. In young infants it tends to be have a more squeaky character.

Its aetiology remains uncertain, but vibrations of the semilunar valves or left ventricular (LV) tendons have been implicated. These qualities distinguish it from other lower precordial murmurs.

VSD murmurs are harsh, loud, and pansystolic or, if the defect is very small, early systolic and decrescendo in character, with a harsh or high-pitched ‘aerosol spray' quality. Mitral regurgitation is rare in children and the murmur is pansystolic, apical, high pitched and blowing, with radiation to the axilla and back.

3. Venous hum

This benign continuous murmur is caused by blood cascading down the great veins.

It is maximally heard in the right infraclavicular region, is accentuated in inspiration and is virtually abolished on lying flat. This contrasts with the harsh, non-positional left infraclavicular continuous so-called ‘machinery' murmur of a patent arterial duct.

4. Carotid bruit

This common harsh, usually short early ESM is caused by flow acceleration from the aortic arch to the brachiocephalic arteries. It is audible in the lower neck and often radiates down to the aortic area, being softer with neck extension or carotid pressure. It should not be confused with aortic stenosis, where the murmur is louder below the clavicle.

5. Pulmonary ESM

This is heard most often in older children or adolescents, is localised to the upper LSB and may be difficult to distinguish from a pathological stenotic murmur (louder with click) or ASD flow murmur (louder).


Ultimately it is the confidence of the GP that will determine whether a child with an innocent murmur is referred. If in doubt, referral is certainly justified, but even in such cases generous reassurance is required to minimise parental concern while awaiting the appointment.

Many parents can be fully reassured by a clear, full explanation. Other parents will not rest until an echocardiogram is performed. The family should be told that their child has a normal heart, requiring no restrictions whatsoever, that the child should be treated normally and that the murmur may be present at one examination but not at another.

A well-written explanatory leaflet is particularly useful as parents often find it difficult to retain information when worried or stressed. By emphasising the benign nature of their child's murmur the leaflet will provide ongoing reassurance.

An excellent leaflet on innocent heart murmurs is available here.

GPs are often under pressure to refer obviously innocent heart murmurs GPs are often under pressure to refer obviously innocent heart murmurs

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