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Hearing “You have a heart murmur” can sound terrifying. It’s easy to imagine dramatic ER scenes and movie-style heart monitors. But in many peopleespecially babies, kids, teens, and pregnant adultsthat sound is simply a flow murmur, also called an innocent, functional, or physiologic murmur. In other words: your heart is making a little background noise, but the hardware is just fine.
This guide walks you through what a flow murmur is, what causes it, how it’s different from a dangerous murmur, what to expect during evaluation, and how it’s usually treated (spoiler: often, it isn’t). We’ll also look at real-life experiences to help this feel less abstract and more “OK, I can handle this.”
Important note: This article is for general information and does not replace medical advice. Always talk with a healthcare professional about your own situation.
What is a flow murmur?
To understand a flow murmur, it helps to know what a heart murmur is in general. A heart murmur is an extra sound your doctor hears through a stethoscopeon top of the normal “lub-dub” of your heartbeat. That extra sound comes from turbulent blood flow inside the heart or major blood vessels.
A flow murmur is a type of innocent or functional murmur. It’s caused by blood moving faster than usual through a heart and valves that are structurally normal. There’s no hole in the heart, no scarred valve, no major defectjust brisk blood flow that makes a little whooshing sound.
Doctors and textbooks use a few different names for the same concept:
- Flow murmur
- Innocent heart murmur
- Functional murmur
- Physiologic murmur
In children, innocent murmurs are incredibly common. Large pediatric studies suggest that the majority of kids will have an innocent murmur at some point in childhood. Many of these murmurs disappear as the child grows and the chest changes shape.
Flow murmur vs. “dangerous” heart murmur
Not all heart murmurs are harmless. Some are a clue to structural heart problems, such as:
- Heart valve narrowing (stenosis)
- Valve leakage (regurgitation)
- Holes in the heart walls (such as ventricular or atrial septal defects)
- Cardiomyopathies (abnormally thick or weak heart muscle)
These are pathologic murmursthey reflect underlying disease and may require medication, monitoring, or even surgery.
Flow murmurs, on the other hand, are like the sound of water rushing through a normal pipe when you turn the faucet on high. Everything is built correctly; it’s just moving quickly. The challenge for doctors is figuring out which murmur is which, which is why evaluation matters.
What causes a flow murmur?
Flow murmurs happen when blood moves more quickly than usual through a perfectly normal heart. Anything that raises blood flow or cardiac output can contribute, including:
1. Normal growth and development in children
Kids’ bodies grow fast, and their hearts work hard to keep up. As the heart and blood vessels change size and position in the chest, blood moving through them can generate extra sound. Common benign murmurs in children include:
- Pulmonary flow murmur – a soft murmur heard best along the upper left chest, where blood leaves the right side of the heart into the pulmonary artery.
- Still’s murmur – a classic vibratory, “musical” murmur heard in many healthy kids, usually at the lower left chest.
- Supraclavicular flow murmur or venous hum – sounds coming from blood flow near the collarbones or jugular veins.
These murmurs often get louder when children lie down (more blood returns to the heart) and softer when they sit or stand up. As they grow, many of these murmurs fade away.
2. Temporary high-flow states
You can have a flow murmur at any age when your heart is working harder than usual, such as:
- Exercise or intense physical activity: High cardiac output can create temporary murmurs, especially in athletes.
- Fever: When you’re sick, your heart rate increases and blood flow speeds up.
- Anemia: With fewer red blood cells, the heart pumps faster to deliver enough oxygen, which can produce a murmur.
- Hyperthyroidism: An overactive thyroid speeds up metabolism and heart rate, increasing blood flow.
- Pregnancy: Blood volume and cardiac output rise significantly, so “pregnancy murmurs” are common.
- Stress or anxiety: Adrenaline can temporarily increase heart rate and blood flow.
In these cases, the underlying heart structure is typically normal. Treating the underlying issuesuch as correcting anemia or managing thyroid diseaseoften makes the murmur disappear.
3. Body build and chest anatomy
Some people simply transmit sound better. A thin chest wall, prominent ribs, or certain body builds can make normal blood flow more audible. Think of it as having better “acoustics”your heart is the same, but the sound carries more clearly to the stethoscope.
Symptoms of a flow murmur
Here’s one of the most reassuring facts: innocent or flow murmurs usually cause no symptoms at all. People feel fine and often learn about the murmur only because a healthcare professional hears it during a routine exam or sports physical.
Because a flow murmur is just a noise, not a disease, you typically will not have:
- Exercise intolerance
- Persistent shortness of breath
- Chest pain related to exertion
- Fainting with activity
- Swelling in the legs or belly
- Bluish lips or fingertips in daily life
However, symptoms can appear if there’s an underlying condition driving the high flow (like severe anemia or hyperthyroidism). In those cases, you might notice fatigue, palpitations, feeling too hot, or unusual shortness of breathsigns that come from the underlying issue, not the murmur itself.
Red-flag symptoms that need urgent evaluation
While flow murmurs are harmless, some murmurs signal more serious heart disease. You should seek medical care promptly if a murmur is associated with:
- Chest pain, especially with exertion
- Fainting or feeling like you might pass out
- Fast or difficult breathing, at rest or with mild activity
- Sudden or severe fatigue
- Bluish or gray lips, tongue, or fingertips
- Swelling of the legs, ankles, or belly
- Poor feeding, poor growth, or trouble breathing in infants
These features raise concern for a pathologic murmur and deserve prompt medical attention.
How doctors diagnose a flow murmur
Deciding whether a murmur is “just a flow murmur” or something more serious is a core clinical skill. Your healthcare professional will combine your story, physical exam, and sometimes tests to make that judgment.
History: your story matters
Your clinician will ask about:
- Any symptoms (shortness of breath, chest pain, fainting, fatigue)
- How active you are and whether you keep up with peers
- Recent illnesses (fever, infections)
- Conditions like anemia, thyroid disease, or pregnancy
- Family history of heart defects, sudden death, or cardiomyopathy
An otherwise healthy person with no symptoms and normal growth (for kids) is more likely to have an innocent murmur.
Physical exam and listening to the heart
Next comes the stethoscope. Clinicians pay close attention to:
- Timing: Flow murmurs are usually heard during systole (when the heart pumps), not during early diastole alone.
- Grade (loudness): Innocent murmurs are typically softer (grade 1–3 out of 6) and don’t have a “thrill” (a vibration you can feel with the hand).
- Location: For example, pulmonary flow murmurs are heard best at the upper left edge of the breastbone.
- Radiation: Innocent murmurs usually stay in a small area, whereas pathologic murmurs may radiate to the neck or back.
- Changes with position: Many flow murmurs get louder when lying down and quieter when sitting or standing.
- Other signs: Normal pulses, normal oxygenation, no signs of heart failure, and a normal second heart sound support a benign cause.
Experienced clinicians can often confidently label a murmur as innocent just by history and examespecially in healthy children with classic features.
Tests used when the diagnosis isn’t obvious
If your healthcare professional wants more information, they may order tests such as:
- Echocardiogram (heart ultrasound) – the gold standard imaging test. It shows the structure of the heart, valves, and blood flow and can confirm that everything is normal.
- Electrocardiogram (ECG) – records the electrical activity of the heart and can reveal rhythm or thickening issues.
- Chest X-ray – sometimes used to see heart size and blood flow patterns in the lungs.
- Blood tests – to check for anemia, thyroid problems, infection, and other causes of high-output states.
For many people with a classic flow murmur, no testing is needed. When tests are done and show a structurally normal heart, the murmur is considered benign.
Treatment for flow murmurs
Here’s the simple version: the flow murmur itself doesn’t usually need treatment. There’s no pill to “quiet the sound” and, more importantly, no need to repair a heart that’s already built correctly.
1. Reassurance and monitoring
The main “treatment” is reassurance. Once your clinician is confident that the murmur is innocent, the plan often looks like this:
- No restrictions on regular activity or sports (unless there’s another reason)
- Routine checkups as usual
- Re-evaluation if new symptoms develop or the murmur changes character
In children, the murmur may fade over time. In adults with a high-flow state that has resolved (for example, after pregnancy), the murmur may also disappear.
2. Treating underlying conditions
If anemia, thyroid disease, infection, or another condition is pushing your heart to pump harder, your provider will focus on treating that problem. As the underlying condition improves, the murmur often softens or goes away.
Examples:
- Anemia: Iron supplements or other treatments to restore healthy red blood cell levels.
- Hyperthyroidism: Medications, radioactive iodine, or other therapies to normalize thyroid hormone levels.
- Fever and infection: Appropriate antibiotics or supportive care.
3. When the murmur is not a flow murmur
If testing or the clinical picture reveals structural heart diseasesuch as valve stenosis, valve leakage, or congenital defectsthen treatment becomes more specific. This might involve:
- Medications to help the heart pump more efficiently
- Procedures such as balloon dilation or catheter-based repairs
- Heart valve surgery in more severe cases
That’s no longer a “flow murmur” situation, but it’s worth mentioning because this is the main reason doctors take any murmur seriously until they’ve ruled out major heart problems.
Living with a flow murmur
Once an innocent or flow murmur is confirmed, life usually goes on as normalwith a little extra story to tell at parties if you like saying, “My heart is so enthusiastic it makes sound effects.”
Activity and sports
Most people with flow murmurs:
- Can play competitive and recreational sports without restriction (unless another condition is present).
- Don’t need special accommodations at school or work.
- Can safely exercise, which is great for heart health overall.
Of course, if you ever develop chest pain, fainting, or unusual shortness of breath with exertion, it’s time to stop and get evaluatedwhether you have a murmur or not.
Do you need antibiotics before dental work?
In the past, many people with heart murmurs received antibiotics before dental or surgical procedures to prevent infections on heart valves (endocarditis). Current guidelines in the U.S. no longer recommend routine antibiotics for people with innocent murmurs and structurally normal hearts. Only those with certain high-risk heart conditions need pre-procedure antibiotics.
Your cardiologist or primary care clinician can tell you whether this applies to you, but for a simple flow murmur in an otherwise normal heart, antibiotics are usually not needed.
When should you see a doctor about a murmur?
You should always get a new murmur evaluated, especially if:
- It was discovered for the first time.
- It sounds different or louder than before.
- You have any concerning symptoms (fainting, chest pain, trouble breathing, or poor growth in a child).
After evaluation, if you’re told it’s a flow murmur, you can usually relax. Still, follow your clinician’s advice about checkups and return sooner if something changes.
FAQs about flow murmurs
Can a flow murmur turn into a dangerous murmur?
Generally, no. A flow murmur reflects a heart that’s structurally normal. However, as you age, it’s always possible to develop unrelated heart conditionsjust like anyone else. If new symptoms appear later in life, they should be evaluated as a fresh problem, not automatically blamed on the old murmur.
Can adults have flow murmurs too?
Yes. While innocent murmurs are especially common in children, adults can have flow murmurs during pregnancy, anemia, fever, intense athletic training, or other high-output states. Often, once the triggering condition resolves, the murmur gets softer or disappears.
Is it safe to ignore a murmur forever?
It’s safe to stop worrying after a qualified clinician has evaluated it and confirmed that it’s innocent. What’s not safe is assuming a murmur is harmless without that initial assessment.
Do flow murmurs show up on tests?
On an echocardiogram, you’ll typically see a structurally normal heart. The ultrasound may show slightly higher flow in some areas, but nothing that requires intervention. ECG and chest X-ray are often normal as well.
Real-life experiences with flow murmurs (500-word extension)
Medical terms can feel cold and abstract, so let’s bring flow murmurs to life with a few very human, everyday scenarios. These are composite, fictional examples based on common patterns that doctors see in clinics.
Case 1: The worried parent and the “musical” murmur
Sophia is a healthy 4-year-old who never stops moving. One day during a routine checkup, her pediatrician pauses mid-exam, frowns thoughtfully at the stethoscope, and says, “I hear a little murmur.” Cue instant parental anxiety.
The doctor explains that Sophia’s murmur is soft, heard only during part of the heartbeat, and gets quieter when she sits up. She’s growing well, has plenty of energy, and has no trouble keeping up with other kids. That combination screams “innocent murmur” to an experienced ear.
To be thorough, the pediatrician refers Sophia to a pediatric cardiologist. The heart specialist listens, reviews her history, and decides she doesn’t even need an echocardiogram. The verdict: a classic Still’s murmurone of the most common flow murmurs in children. No medicine, no activity limits, and no special precautions needed.
A year later, the murmur is softer. By the time Sophia reaches middle school, it’s gone entirely. Her parents’ biggest complaint now? She runs too muchmostly in the direction of soccer fields.
Case 2: The athlete and the surprise murmur
Jordan is a 17-year-old varsity runner getting a pre-season sports physical. He’s been training hard and feels great. During the exam, the clinician hears a systolic murmur at the upper left chest. Jordan’s heart sinkshe’s heard stories of athletes being sidelined by heart issues.
Because athletes can have both normal high-output murmurs and serious underlying conditions (like hypertrophic cardiomyopathy), Jordan’s clinician takes it seriously. He orders an echocardiogram and ECG.
The results: Jordan’s heart is structurally normal, his walls and chambers look great, and the murmur likely reflects vigorous blood flow from his well-conditioned heart. He’s cleared to compete, with the recommendation to report immediately if he ever has chest pain, fainting, or shortness of breath out of proportion to training.
Jordan walks out of the clinic with a new appreciation for his heartand maybe a story to tease his teammates: “I’m so fit, even my blood flow is loud.”
Case 3: Pregnancy, a racing heart, and reassurance
Amelia is 28 and pregnant with her first baby. In her second trimester, she notices her heart pounding more often. Her OB-GYN hears a soft murmur along the upper chest and sends her to a cardiologist “just to be safe.”
The cardiologist explains that during pregnancy, blood volume can increase by 30–50%, and the heart works harder to pump that extra volume. It’s normal to hear a new flow murmur and feel a faster heartbeat. An echocardiogram confirms a normal heart, normal valves, and a healthy increase in cardiac output consistent with pregnancy.
Amelia receives some practical advice: stay hydrated, rise slowly from sitting, and report any severe chest pain, fainting, or shortness of breath. Her pregnancy progresses smoothly. After delivery, the extra blood volume gradually drops, and by her postpartum checkup, the murmur is barely audible.
What these experiences have in common
In every story, the key steps are the same:
- Someone notices a murmurduring a routine exam, sports physical, or pregnancy visit.
- A clinician evaluates the person’s overall health, symptoms, and family history.
- A careful physical exam, and sometimes tests, confirm that the heart’s structure is normal.
- The murmur is labeled “innocent” or “flow,” and life goes onoften with a big dose of relief.
The takeaway? A flow murmur is usually your heart’s way of saying, “I’m working, and I’m doing it well.” It deserves a proper checkup, but once an expert gives you the all-clear, you can focus less on the sound and more on keeping your heart healthy with sleep, movement, stress management, and nourishing food.
