Heart Murmurs in Children

Heart murmurs are due to abnormalities of flow within the heart and great vessels. Innocent murmurs are very common but it is essential to assess whether the murmur is haemodynamically significant and whether appropriate antibiotic prophylaxis to prevent endocarditis is required. If there is any doubt, referral to a general paediatrician or paediatric cardiologist is essential.

The absence of symptoms does not exclude important pathology. Murmurs are described by location, intensity (grade 1-6 with grade 1 being virtually undetectable), timing in the cardiac cycle, and radiation.
Certain features indicate that a murmur is more likely to be pathological and that prompt expert evaluation is needed:¹

• History: lethargy, tiredness, failure to thrive
• Inspection: cyanosis, clubbing, abnormal breathing (tachypnoea, intercostal recession)
• Palpation: parasternal or apical impulse; abnormal pulses - diminished, absent or delayed femoral pulses
• Abnormal heart sounds; second heart sound is accentuated and not variably split
• Systolic murmur which is pansystolic or is grade 3 or above
• Murmur which is purely diastolic
• Radiation of murmur to the back
• Presence of an early or midsystolic click
• Presence of cardiac failure or arrhythmia

• Still's murmur: the commonest innocent murmur in children (usually heard at age 3-6 years, although also occasionally in infants). Short, midsystolic murmur with a very characteristic low-frequency buzzing or musical quality. It is localised to the lower left mid-sternal border and radiates to the apex. The murmur is of short duration, low intensity and is loudest when the child is supine, often varying markedly with posture. It can be made to disappear on hyperextension of the back and neck (Scott's manoeuvre). However it is not always possible to distinguish it from a small ventricular septal defect.
• The venous hum is a superficial continuous murmur heard beneath the clavicles and in the neck. It is more often heard in the right than left side and most easily when the child is upright. It can be abolished by head movements, by compression of the jugular vein on the same side, or by lying the child supine.
• Pulmonary flow murmur is a soft early to mid-systolic ejection murmur heard at the upper left sternal border but does not radiate to the back. In premature and newborn infants, an innocent soft ejection murmur can be heard at the base with radiation into the axillae and even the back. This originates in the proximal pulmonary artery branches. It disappears before 1 year of age.
• Apical murmur: localised, apical, high pitched midsystolic murmur.
• Innocent carotid bruits are common in normal children. It is midsystolic and is best heard in the neck just above the clavicle, often radiating down to the aortic area. Aortic stenosis is differentiated by its murmur being louder below the clavicle than above.

• Ejection systolic murmurs: reach a peak midway between 1st and 2nd heart sounds and don't run into 2nd heart sound. Usually maximal at the upper sternal borders and possible causes include:
  • Aortic stenosis
  • Pulmonary stenosis
  • Coarctation of the aorta: murmur is heard over the back particularly in the interscapular region
  • Hypertrophic obstructive cardiomyopathy
• Pansystolic murmurs have uniform intensity between 1st and 2nd heart sounds and merge with the 2nd heart sound, which is therefore not distinguishable. Those at the lower sternal border are more likely to be of regurgitant type due to:
  • Ventricular septal defect
  • Atrial septal defect
  • Mitral or tricuspid regurgitation

• Diastolic murmurs should always be regarded as pathological.
• Early diastolic murmurs: occur just after the 2nd heart sound. They are high pitched and easily missed. causes include aortic valve regurgitation (e.g. bicuspid aortic valve, Marfan's syndrome) and pulmonary valve regurgitation (e.g. following surgery for Fallot's Tetralogy or pulmonary stenosis), or with pulmonary hypertension.
• Mid or late diastolic murmurs: are low pitched and occur at the lower sternal borders in mitral stenosis or tricuspid stenosis.

Cross the 2nd heart sound and are a feature of:

• Venous hum (otherwise they are always pathological)
• Persistent ductus arteriosus
• Arteriovenous malformation

• The chest X-ray, ECG and echocardiogram add little or no information in a child clinically assessed to have an innocent murmur.²
• An echocardiogram is the the gold standard for the diagnosis of a structural heart disease but is not routinely required.³
• Cardiac catheterisation is occasionally necessary.

If there is any doubt, referral to a general paediatrician or paediatric cardiologist is essential.⁴