Cardiac murmurs in infancy

Heart murmurs are central diagnostic elements to suspect the existence of congenital heart disease, whose incidence is 1%.

Auscultation of a murmur in pediatrics is a fairly frequent finding. It is an extra noise detected in the auscultation of the child and it is estimated that up to 80% of children will present it at some stage of their lives.

Murmurs are classified on a scale of intensity from 1 to 6, with grade 1 being barely audible and grade 6 being very loud.

The main problem we face when dealing with a child with a murmur is to determine whether it is pathological or not. Therefore, referral to a Cardiologist with experience in Congenital Heart Disease is a very appropriate option for the correct diagnosis of the type of murmur and the exclusion of any heart disease that would make the child require specific treatment and follow-up of its pathology.

Evaluation of the cardiac murmur in children

1. Anamnesis: The presence of any of these findings requires a more complete evaluation of the child:
   • Murmur in the first 48 hours of life and recommended in infants (since 1 in 7 infants with murmur have underlying heart disease).
   • In neonates and infants, feeding difficulty, poor weight gain, unexplained respiratory symptoms or cyanosis. In schoolchildren and adolescents, the presence of chest pain, syncope, exercise intolerance or palpitations.
   • Pregnancy history: prematurity, maternal Diabetes Mellitus type 1, infections or medication intake.
   • Family History: congenital heart disease, hypertrophic cardiomyopathy and sudden death under 40 years of age.
2. General Physical Examination: The existence of any of these findings requires further evaluation:
   • Skin: cyanosis.
   • Chest configuration: asymmetries, malformations, scoliosis.
   • Type of breathing: tachypnea.
   • Weight and height: poor stature-weight gain.
   • Blood pressure: asymmetric parameters (check the 4 extremities for aortic coarctation).
   • Palpation of precordium and apex: displacement may indicate cardiomegaly.
   • Palpation of the liver: signs of congestive heart failure.
   • Dysmorphia (25% are associated with congenital heart disease).
3. Auscultation: An auscultation can be considered pathological when it meets one of these criteria:
   • Pansystolic murmur.
   • Proto- or mesosystolic clicks.
   • Alteration of the second sound.
   • Diastolic murmur.
   • Intensity greater than III/VI.
   • Rough or rough quality.

Innocent murmur versus pathologic murmur

Innocent murmurs are defined as those that are heard in an absolutely normal heart, during childhood or adolescence, and that have no clinical significance. The literature makes a difference with Functional Murmur, which is defined as a murmur present in a healthy heart, but which is secondary to a non-cardiac pathology (e.g. thyrotoxicosis, anemia, fever).

Characteristics of innocent murmurs

In general terms, functional murmurs share some common characteristics that allow their suspicion:

1. They are auscultated in children without precordial activity.
2. Auscultation of the first sound (R1) is normal.
3. A dissociation of the second sound (R2) may be auscultated, but it is modified by breathing.
4. When auscultated with the child in the supine position, the murmur is heard “diamond-shaped”.
5. When the child is auscultated while standing, the intensity of the murmur decreases.
6. With the exception of the venous “Hum”, all functional murmurs are systolic.

What is the most appropriate behavior in the presence of a murmur?

– In the presence of warning signs: refer to a Cardiologist with experience in Pediatric Cardiology for Echocardiography since this method has a sensitivity and specificity of around 100%.

– In the absence of warning signs, differentiate according to the age of the child:

• Under 6 months old: if there is a high suspicion of Physiological Pulmonary Branch Stenosis, it is considered a control until 6 months of age. If the murmur does not disappear, refer to a cardiologist.
• Between 6 months and 2 years: refer all murmurs to the cardiologist, considering the difficulty in examining these children and that 1 in 7 will be pathological.
• Older than 2 years: assume as innocent murmur and educate parents about the normality of the condition and the absence of restrictions. However, in most cases, a referral to a cardiologist is usually made to confirm the absence of pathology by performing Color Doppler-Echocardiography.

The importance of the cardiologist in cardiac murmurs

Auscultation is the initial diagnostic method in innocent murmurs, however, it is required to be complemented by a complete anamnesis and physical examination, and directed to look for warning signs.

Referral to a cardiologist with experience in Cardiology and Infant Echocardiography should be made in case of diagnostic doubt and always in children between 6 months and 2 years of age.

Echocardiography is the method of choice to rule out congenital heart disease.