Heart murmurs in children

See also the separate Heart Auscultation article.

Heart murmurs are common in asymptomatic and otherwise well children. Many murmurs are innocent and result from normal patterns of blood flow through heart and blood vessels¹.

However, a murmur can be the sole manifestation of structural heart disease. More than 50% of newborns with congenital heart disease are unrecognised at birth². Therefore, a careful evaluation is essential. If in doubt, referral to a paediatrician with expertise in cardiology (PEC) or a paediatric cardiologist is necessary.

Presentation

Does this child have heart disease?³

The key question which is raised on the detection of a heart murmur is: 'Does this child have a heart disease?' To answer this, three groups of factors need to be considered:

1. Are there any symptoms and signs of heart disease?

2. Are there any predisposing medical conditions?

3. What are the characteristics of the murmur?

Symptoms of heart disease

The symptoms vary with the age of the child and are more nonspecific in infants. One or more of the following may be present:

Signs of heart disease

Predisposing medical conditions

• Down's syndrome

• Noonan's syndrome

• Turner syndrome

• Marfan's syndrome

• Fetal alcohol syndrome

• Fetal rubella infection

Characteristics of the murmur

Each heart murmur must be analysed in terms of intensity (grades 1 to 6), timing (systolic or diastolic), location, transmission and quality (musical, vibratory, blowing, harsh, etc).

A grade 1 murmur is barely audible, grade 2 is soft but easily heard, grade 3 is loud but not accompanied by a thrill, while grade 4 is associated with a thrill. Grade 5 and 6 are very loud murmurs which may be audible with stethoscope partly or completely off the chest.

Most murmurs are systolic and location of a systolic murmur can point toward specific cardiac diagnosis as described in the table below:

Likewise timing of the murmur can help in identifying the cause of the murmur:

Pathological murmurs

Diastolic murmurs are pathological. Six cardinal signs are described which indicate that a systolic murmur is likely to be pathological, ie because of an underlying heart defect. These are:

• Holosystolic (pansystolic) murmur.

• Harsh murmur.

• Abnormal heart sounds.

• Early or mid-systolic click.

• Grade 3 murmur or greater.

• Heard over upper left sternal border.

Innocent murmurs⁴

• Sensitive (changes with child's position or with respiration).

• Short duration (not holosystolic).

• Single (no associated clicks or gallops).

• Small (murmur limited to a small area and not radiating).

• Soft (low amplitude).

• Sweet (not harsh-sounding).

• Systolic (occurs and is limited to systole).

Five types of innocent murmurs in childhood are described, all with diagnostic clinical features. However, the differential diagnosis always includes pathological murmurs because of various heart defects. These are summarised below:

Neonatal heart murmurs

Heart murmurs in neonates are much more likely to indicate structural heart disease and should prompt specialist assessment.

One study of 6,333 healthy newborn babies found heart murmurs in 87 (1.37%) neonates, of whom 42.5% had a structural cardiac malformation. Ventricular septal defect (62%) was the most common diagnosis, followed by atrial septal defect, pulmonary stenosis and patent ductus arteriosus⁵.

Even potentially life-threatening heart defects may have no other signs or symptoms in addition to the heart murmurs. A very thorough evaluation including detailed clinical examination, femoral pulse check along with pulse oximetry (pre- and post-ductal saturations) is mandatory. Those with clinical signs, difficult-to-palpate femoral pulses or low oxygen saturations require prompt echocardiographic assessment. Neonates with heart murmurs who are clinically asymptomatic should also be referred for a routine echocardiographic assessment.

Investigations

ECG and CXR have limited use in the diagnosis of underlying pathology associated with pathological heart murmurs, with low sensitivity and specificity for identifying cardiac defects or anatomical abnormalities.

Echocardiography is the gold standard to diagnose congenital cardiac malformations definitively in paediatric patients. It is indicated in any child with an asymptomatic heart murmur which has attributes of a pathological murmur or when the examiner is not comfortable in making a clinical diagnosis of an innocent heart murmur. This can usually be done by a PEC in a district general hospital setting, minimising the need for referral to a tertiary cardiology service⁶.

Management

Any child found to have a heart murmur should have a thorough clinical evaluation including pulse oximetry and palpation of femoral pulses. Clinically unwell children or those with red flags such as difficult-to-feel femorals or low oxygen saturations need urgent referral for specialist cardiac evaluation. It is important to remember that absence of symptoms does not exclude important pathology. If in doubt, referral to a PEC or a paediatric cardiologist is essential. The American College of Cardiology recommends a low threshold for echocardiographic evaluation of heart murmurs, as shown below⁷.

Evaluation of murmurs⁷

Systolic murmurs
Midsystolic:

• Grade 2 or less:
  

  • Asymptomatic and no associated signs - no further workup.

  • Symptomatic or other signs of cardiac disease - echocardiogram.

• Grade 3 or more - echocardiogram.

Early systolic, late systolic, holosystolic:

• Echocardiogram.

Diastolic and continuous murmurs
All diastolic and continuous murmurs must be evaluated using echocardiography.

The National Institute for Health and Care Excellence (NICE) no longer recommends routine antibiotic prophylaxis in children with structural heart disease but emphasises the importance of maintaining good oral health⁸.

Patient and family education

Once a heart murmur is confirmed to be innocent, reassurance to the family regarding its benign nature is important. Although the murmur may never disappear and may persist into adulthood, the parent and child need to be specifically reassured that an innocent murmur is simply an additional noise audible to the clinician and not a disease or illness, and is therefore completely harmless.