Auscultation of Murmurs and Other Heart Sounds: A Quick Guide for Physicians

Auscultation of Murmurs and Other Heart Sounds: A Quick Guide for Physicians

Evaluating heart sounds in children can be a challenge at times.  In pediatrics it is best to examine the child with a stethoscope directly on the skin and in an environment as quiet and distraction free as possible.  That may mean 1) listening to the heart before doing anything else that might disturb the child or 2) letting the child feed and fall asleep before trying again at a later point in time.  In older children it can be helpful to have the child hold their breath in order to focus on the murmur without the interference of breath sounds.

In general, I exclusively use the diaphragm of the stethoscope with firm pressure to amplify the sound. Although pediatric stethoscopes tend to have a small head with long tubing, most pediatric cardiologists prefer the larger diaphragm and shorter tubing as this results in better amplification of heart sounds.

Deciding if a murmur is pathological or innocent can be done with certain criteria. 

One approach is to assess the characteristics of the murmur.

Timing: If the murmur is systolic it is more likely to be innocent.  If it is diastolic or holosystolic (also known as pansystolic) it is likely pathologic.

Grade: A grade 1 or 2 systolic murmur is more likely to be innocent than a loud murmur (grade 3 or higher), or those associated with a thrill (grades 4,5, and 6).

Pitch: An innocent murmur is likely to be soft and vibratory or medium pitch rather than harsh or high-pitched.

Second heart sound: A very loud second heart sound, single second heart sound, or widely split-second heart sound represents pathology.

Radiation: A murmur is described as “radiating” when it is nearly as loud in another location of the torso as it is in the chest. This phenomenon is suggestive of a pathologic murmur.   For instance, a murmur heard in the left third or fourth interspace that is equally loud in the back is suggestive of coarctation of the aorta.  Another example would be a murmur heard best at the upper right and upper left sternal border radiating to the carotid arteries.  One must take care to distinguish this from transmission. A murmur would be considered transmitted rather than radiating when it is much less intense/loud at the other spot. Transmission of a murmur to other areas is a bit more likely if the child is particularly thin or anxious.

Clicks: A murmur is likely to be pathological if there is an associated click.

A second approach is to assess the characteristics AND the change in the murmur with body position.

In this approach the murmur is first checked in the typical sitting and supine positions, followed by the standing position.  A murmur that resolves upon standing is likely an innocent murmur, though this may not be the case with an atrial septal defect. If the murmur is louder with standing, it is likely pathological.  This is useful in teens being screened for sports physicals where there is an increased concern for hypertrophic cardiomyopathy. After initial auscultation the patient is instructed to squat and then stand up.  In this maneuver, if the patient has hypertrophic cardiomyopathy, the murmur will be absent or very soft when squatting and manifest or get louder when standing.

Cautions

Don’t push too hard if listening to the carotid artery or the femoral artery as that can create a sound resembling a bruit or radiation of the murmur.  To get a better appreciation of transmission, listen to other sites such as the carotid arteries and the back in children known to have an innocent murmur as you can occasionally hear the murmur softly in those areas as well. If you have referred a child for a murmur evaluation, listen to them the next time you assess the patient and compare your findings to the cardiology consult note.  In a young child in whom you think may have an innocent venous hum murmur, it is necessary confirm that the murmur resolves when the child is supine to avoid misdiagnosing a pathological murmur from a PDA. 

One cardiac lesion whose murmur can be difficult to distinguish from an innocent murmur is the atrial septal defect.  In these cases, the murmur is not actually coming from blood flow across the atrial defect (since the atrial pressures are low on either side) but instead the murmur arises from the significantly increased blood flow crossing the right ventricular outflow tract and pulmonary valve.  These people will have a murmur that sounds like a pulmonary flow murmur, but the tip-off is that the second heart sound is widely split.  The widely split-second heart sound will not vary with respirations.  It is a fixed split.  In a normal situation the second heart sound may increase during inspiration and nearly become single with expiration; this is physiologic splitting.  An atrial septal defect is one of the more commonly missed diagnoses in individuals who are felt to have an innocent murmur.  Another commonly missed diagnosis is coarctation of the aorta in young children but that relies more on the ability to discern the femoral pulses or pedal pulses rather than the typical murmur of coarctation.

In some situations, the absence of a murmur does not convey the absence of congenital heart disease. For example, among newborns with Down syndrome and a large AV canal defect, elevated pulmonary pressures normally seen after birth in these children may result in no murmur.  Also, people with non-obstructive cardiomyopathy may not have a murmur.  It is our belief that all babies with Down syndrome should have either a fetal echo or postnatal echo.  We also believe that all first-degree relatives of a person with hypertrophic cardiomyopathy should be assessed by a pediatric cardiologist.

People may feel uncomfortable assessing murmurs because they assume that their hearing may not be good enough.  You should assume your hearing is good enough.  Generally, recognizing a murmur is best accomplished with training to hear the murmur and to recognize it; most people can hear it.  The training is best done with listening to samples of heart sounds both normal and abnormal as well as murmurs.  Studies have shown that a high percentage of students can be trained to differentiate murmurs but that unless that recognition skill is practiced and refreshed it is rapidly lost over time.

Below you will find a link to free sampling of the heart sounds and murmurs that in my opinion are acoustically accurate and very helpful.

http://www.med.umich.edu/lrc/psb_open/html/repo/primer_heartsound/primer_heartsound.html

Marc LeGras, MD