A doctor listens to a child's chest for a few seconds and says the word "murmur," and within that short sentence a parent's whole afternoon changes. The good news usually arrives just as quickly, because most of the time what follows is reassurance. Doctors split murmurs into two broad groups: innocent and pathological. Telling them apart isn't guesswork. It comes down to a specific set of listening cues that every trained clinician learns early and uses constantly.

An innocent murmur is simply a normal heart doing normal things a little more audibly than usual. Nothing is structurally wrong. Blood is moving through healthy chambers and valves, and in a child's chest, thin, fast-beating, close to the surface, that movement is easier to pick up than it would be in an adult. A pathological murmur points to something different underneath it: a hole between chambers, a narrowed or leaky valve, an abnormal connection between vessels. The sound itself is a clue to the anatomy behind it.

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So what does a doctor actually listen for?

Timing within the heartbeat matters a great deal. Innocent murmurs almost always occur during systole, the contraction phase, and tend to be short, soft and musical. A murmur heard between heartbeats, in diastole, is treated with far more suspicion by default. Loudness is graded from one to six, and while grade alone never confirms or rules out a structural cause, a loud or harsh murmur, particularly one that can be felt as a vibration through the hand as well as heard through a stethoscope, pushes the assessment toward further investigation.

Where the sound is loudest, and whether it spreads to the neck, the back or the armpit, helps narrow down which valve or vessel is producing it. A murmur confined to one small patch of chest behaves differently to one that carries across the whole precordium. Doctors also watch how a murmur changes with position. A pathological murmur tends to stay far more constant whatever position the child is in.

The child's appearance matters as much as the sound itself. A murmur in a well-grown, symptom-free child who feeds normally, breathes normally and has good colour carries a different weight to the same grade of murmur in a baby who tires during feeds or breathes fast at rest. Two children can have murmurs of similar loudness, and the clinical picture behind each one can be completely different.

There's a reason this can't always be settled at the first listen. Even experienced clinicians sometimes can't be fully sure from the stethoscope alone, particularly in a wriggling toddler or a crying baby. That's not a gap in anyone's skill. It's simply the limit of what sound alone can tell you, and it's exactly why an echocardiogram exists as the next step whenever there's real doubt. An echo removes the guesswork entirely, because it shows the heart's actual structure and blood flow rather than inferring it from an acoustic signature. Dr Giardini performs and reviews the echocardiogram in the same appointment wherever possible, so families very rarely leave without a clear answer.

Parents sometimes ask why a murmur wasn't picked up at an earlier check and only turned up months later. This happens a lot and rarely means anything was missed. Innocent murmurs can become louder during illness, fever or a growth spurt, simply because faster blood flow makes the sound easier to hear, and a quiet, uncooperative baby at one appointment might settle into an easy, calm examination at the next.

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❓Frequently asked questions

Can a pathological murmur sound the same as an innocent one?

‍Occasionally, yes, which is exactly why listening alone isn't always the final word. A few conditions, subaortic stenosis in particular, can mimic the sound of the common Still's murmur closely enough that an echocardiogram is the only way to be fully sure.

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Does a louder murmur always mean a more serious problem?

‍No. Grade reflects volume, not severity. A loud innocent murmur is still innocent, and some significant structural conditions produce surprisingly soft murmurs, so loudness on its own never decides the outcome.

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Can a murmur be innocent at one appointment and pathological at another?

‍The heart underneath doesn't change type. What can happen is that an innocent murmur becomes louder or quieter over time, or a new murmur appears for a separate, acquired reason, which is one reason any new murmur in an older child is always worth checking rather than dismissed as old news.

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Do doctors ever disagree about whether a murmur is innocent?

‍It happens, particularly with softer or borderline murmurs, and it isn't a sign either doctor got it wrong. It reflects real acoustic overlap between the two categories, and it's a perfectly reasonable reason to want a specialist opinion for a clear answer.

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Is an echocardiogram needed for every murmur?

‍Not for every murmur, but it's recommended whenever there's any uncertainty after the clinical examination, any murmur in a newborn, or any murmur alongside symptoms such as poor feeding, breathlessness or slow weight gain. Dr Giardini can advise after examination whether one makes sense for your child specifically.

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Author: Dr. Alessandro Giardini, MD, PhD, Consultant Paediatric Cardiologist

Written 05/08/2026

Last reviewed 05/08/2026