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Page 2 of 24 Rao. Vessel Plus 2022;6:22 https://dx.doi.org/10.20517/2574-1209.2021.105

prior to afore-mentioned investigative studies, particularly in children. Such an assertion, however, is not
applicable in neonates because (1) severe cyanotic congenital heart defects (CHDs) can exist without a
cardiac murmur; (2) a loud murmur does not automatically suggest that the reason for the distress in the
baby is related to a heart defect; and (3) when a murmur is detected, it is not necessarily characteristic of a
specified CHD, as emphasized elsewhere . Therefore, the discussion in this paper is mainly focused on
[3,4]
murmur evaluation in children and not in neonates.

In this paper, the cardiac murmur is defined, the prevalence of the murmurs is cited, an approach to
auscultation is presented, murmurs are classified, and the differential diagnosis of the cardiac murmurs is
detailed.

Definition of cardiac murmurs
Cardiac murmurs are defined as abnormal sounds or vibrations that originate in the heart and/or large
blood vessels and are usually auscultated in the precordium and/or great vessel sites. The sound frequency
of the vibrations varies from 50 to 1000/s. The word “murmur” is used for abnormal vibrations of a longer
period, whereas the shorter duration vibrations are termed snaps or clicks. A murmur auscultated at the
peripheral vascular sites is named “bruit”; for example, carotid bruit for a sound appreciated over the
carotid vessels and abdominal bruit for a sound perceived across the abdominal aorta region. Conversely, a
bruit heard over the precordium is called a murmur. The pattern of normal blood flow in the cardiovascular
structures is assumed to be laminar. A murmur is believed to be produced once turbulence is formed
[5]
secondary to an abnormal flow pattern . It is commonly thought that an audible murmur is heard when the
Reynolds number is in excess of 2000 :
[5]
Reynolds number = rQD/u

D means blood density, Q indicates blood flow velocity (mean), r means conduit (tube) radius, and u
indicates viscosity of the blood.

Prevalence of murmurs
Cardiac murmur is the most frequent abnormality by which heart disease is detected, especially in children
(not neonates). Furthermore, in the author’s personal experience, murmur is the most frequent reason for
calling for an appointment for a child to see a pediatric cardiologist for evaluation of the heart. On routine
auscultation, cardiac murmurs in the neonates and premature infants are somewhat infrequent (< 2%).
However, during careful auscultation, heart murmurs may be appreciated in excess of half of these babies,
and the prevalence may be in the order of 80% in normal preterm babies . In otherwise normal children
[5]
and teenagers, the prevalence of cardiac murmur varies from 30% to 50%. However, most of these are
[5]
functional, normal, or innocent murmurs and should not be of any concern . Recent studies also indicated
that the majority of the murmurs are functional murmurs whether the examination is performed for routine
screening or as a part of pre-sports participation screening .
[6,7]

An approach to auscultation
It is essential that the patient is quiet, and the auscultation should take place in noiseless surroundings so as
to ensure accurate interpretation of auscultatory findings. In young babies and toddlers, it is critical to listen
to the chest first before the infant is disturbed with the examination of the liver, palpation of the femoral
pulses, or even precordium. Of course, ear and throat examination should not be performed prior to
auscultation. Young infants are better examined initially on the mother’s lap.