Innocent Heart Murmurs
in Children
Your child’s doctor said they have a heart murmur. Before you panic — most murmurs in children are completely normal sounds, with no heart disease whatsoever. Here is exactly what that means.
What Is an “Innocent” Murmur?
A murmur is simply the sound of blood flowing through the heart. An innocent murmur (also called a “functional” or “benign” murmur) is a sound produced by normal blood flow — there is no hole, no faulty valve, no structural problem. The heart is perfectly normal. These murmurs are extremely common and require no treatment, no restrictions, and no follow-up in most cases.
Why Do Innocent Murmurs Occur?
When blood flows through the heart and great vessels, it normally does so smoothly and silently. But in children — especially during times of fever, excitement, anaemia, or rapid growth — the blood may flow more turbulently, creating an audible sound. This is completely normal physiology. The heart itself is structurally perfect.
Moss & Adams (10th Edition, Chapter 9) describes five distinct innocent murmurs seen in children, each with characteristic features that allow a trained cardiologist to identify them confidently with a stethoscope alone — without needing any tests.
The “PASS” Features of All Innocent Murmurs
- Positional change — murmur changes intensity with position
- Asymptomatic — no symptoms (no cyanosis, no breathlessness, no poor feeding)
- Soft — grade I–II (low intensity)
- Short — systolic only (except venous hum), no clicks, no radiation
Where Each Innocent Murmur Is Heard — Auscultation Map
| # | Murmur Type | Location Heard | Key Feature |
|---|---|---|---|
| 1 | Still’s Murmur | Apex → L sternal border | Vibratory, musical quality |
| 2 | Pulmonary Flow | Upper L sternal border | Systolic ejection, soft |
| 3 | Carotid Bruits | Neck, over carotid arteries | Decreases with compression |
| 4 | Peripheral Pulmonary | Heard in axillae (newborns) | Disappears by 3 months |
| 5 | Venous Hum | R infraclavicular / supraclav. | Continuous; disappears lying down |
The five types of innocent murmurs and their characteristic auscultation sites. All are systolic (except venous hum which is continuous) and have normal cardiac anatomy.
The Five Innocent Murmurs of Childhood
Moss & Adams describes five distinct types of innocent murmurs, each with specific characteristics that allow confident clinical identification:
Still’s Murmur — The Most Common Innocent Murmur
First described by Dr. George Frederick Still at Great Ormond Street Hospital in London in 1909. This is the most common innocent murmur of childhood, typically heard in children aged 2–7 years.
Innocent Pulmonary Flow Murmur
A soft systolic murmur heard at the upper left sternal border (pulmonary area), caused by normal turbulent blood flow through the pulmonary valve into the pulmonary artery. Very common in children and adolescents, especially during fever or anaemia.
Carotid Bruits
Systolic ejection sounds heard over the carotid arteries in the neck, caused by turbulent blood flow as blood passes from the wider aorta into the narrower carotid arteries. This is a completely normal finding and is not evidence of carotid artery disease (unlike in adults).
Peripheral Pulmonary Branch Stenosis of the Newborn
A systolic ejection murmur unique to newborns in the first 3 months of life. It arises because the pulmonary artery branches are relatively small and immature at birth, creating turbulence. As the branches grow, the murmur disappears naturally.
Venous Hum — The Unique Continuous Murmur
The only innocent murmur heard in both systole AND diastole (continuous murmur). It is caused by turbulent venous blood flowing through the internal jugular and subclavian veins into the superior vena cava. Its position-dependence is its defining characteristic.
Innocent vs. Pathological Murmurs — How Cardiologists Tell Them Apart
Innocent vs. Pathological Murmur — Feature Comparison
| Feature | ✅ Innocent Murmur | ⚠️ Pathological Murmur |
|---|---|---|
| Intensity | Grade I–II (soft) | Grade III+ (louder, may thrill) |
| Timing | Systolic only* | Diastolic always pathological |
| Second Heart Sound (S2) | Normal splitting | Fixed split (ASD) / Single (severe PS) |
| Clicks | Absent | May be present |
| Radiation | None | May radiate to neck, back, axilla |
| Varies with position | Yes — typically softer when lying | Unchanged |
| Echo Required? | No (if clearly innocent) | Yes — always |
Key distinguishing features between innocent and pathological murmurs. Any diastolic murmur, click, radiation, or S2 abnormality warrants echocardiography.
The 5 Innocent Murmurs — Quick Reference Table
| # | Murmur | Location | Timing | Key Feature | Age |
|---|---|---|---|---|---|
| 1 | Still’s Murmur | Apex → L lower sternal border | Systolic | Musical / vibratory quality | 2–7 years |
| 2 | Innocent Pulmonary Flow | Upper L sternal border | Early systolic | Normal S2 (no split) | 8–14 years |
| 3 | Carotid Bruits | Neck (over carotids) | Systolic ejection | Diminishes distally; normal in children | Any age |
| 4 | Peripheral Pulmonary Branch Stenosis | Axillae bilaterally | Systolic ejection | Disappears by 3 months | Newborn (0–3 months) |
| 5 | Venous Hum | R infraclavicular / supraclavicular | Continuous (S + D) | Disappears lying flat (supine) | 3–8 years |
When a Murmur Is NOT Innocent — Warning Signs
- Murmur heard in a newborn in the first 24 hours of life (may indicate critical CHD)
- Diastolic murmur at any age
- Grade III or louder murmur
- Murmur with a palpable thrill (vibration felt by hand on chest)
- Associated symptoms: cyanosis (blue lips/fingertips), poor feeding, failure to thrive, excessive sweating, breathlessness
- Fixed split second heart sound (suggests ASD)
- Ejection click (suggests bicuspid aortic valve or pulmonary stenosis)
Frequently Asked Questions
🎯 Key Takeaways for Parents
An innocent murmur means the heart is structurally normal — it is a sound of normal blood flow, not a sign of disease.
There are 5 types of innocent murmurs in childhood: Still’s, innocent pulmonary flow, carotid bruits, peripheral pulmonary branch stenosis of the newborn, and venous hum.
No treatment is needed. No restriction on activity. No special precautions.
Innocent murmurs can get louder with fever, excitement, or anaemia — this is normal and doesn’t mean anything worrying has changed.
The key features of innocent murmurs: soft (grade I–II), systolic, no radiation, normal S2, asymptomatic, positionally variable.
If any doubt exists — especially with diastolic murmurs, murmurs with symptoms, or grade III+ murmurs — a pediatric cardiology evaluation is always appropriate.
