Home H Cardiovascular Conditions Heart murmur: Causes by Age, Symptoms, Diagnosis, and Next Steps

Heart murmur: Causes by Age, Symptoms, Diagnosis, and Next Steps

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A heart murmur is a sound a clinician hears through a stethoscope when blood moves through the heart or nearby vessels. Many murmurs are harmless, especially in children and during pregnancy, and they never cause symptoms or require treatment. Others are clues that a valve is narrowed or leaky, that there is a hole between heart chambers, or that the body is in a “high-flow” state such as fever or anemia. Because a murmur is a finding—not a diagnosis—the next step is figuring out whether it is innocent or a sign of structural heart disease. This article explains what murmurs mean, why they happen, who should be evaluated sooner, what symptoms raise concern, how clinicians confirm the cause (often with an echocardiogram), and what treatment and follow-up look like when a murmur is linked to an underlying condition.

Table of Contents

What a heart murmur is and what it means

A heart murmur is an extra sound layered on top of normal heart sounds. Clinicians describe it as whooshing, blowing, rumbling, or harsh. The sound forms when blood flow becomes more turbulent than usual. Turbulence can be completely normal (for example, in a healthy child with a thin chest wall) or it can happen because blood is forced through a narrowed opening or leaks backward through a valve.

Two ideas make murmurs much easier to understand.

First, timing matters. Murmurs are categorized by when they occur in the heartbeat:

  • Systolic murmurs happen when the heart pumps blood out. Many innocent murmurs are systolic, but important valve problems can be systolic too.
  • Diastolic murmurs happen when the heart relaxes and fills. These are more likely to be abnormal and should be evaluated.
  • Continuous murmurs occur throughout the cycle and can reflect unusual connections between vessels.

Second, a murmur is not a diagnosis. It is a clue that points toward categories of causes:

  • Innocent (functional) murmur: no structural heart problem. Common in children; also seen with pregnancy, fever, anxiety, thyroid overactivity, or anemia.
  • Structural murmur: caused by an abnormal valve, a congenital heart defect, thickened heart muscle, or other heart disease.
  • Flow murmur from high output: the heart is normal, but blood flow speed is high (fever, severe anemia, pregnancy).

Clinicians also describe intensity using a grading scale from 1 (very soft) to 6 (very loud). Loudness alone does not prove severity, but very loud murmurs—especially those with a palpable vibration on the chest—deserve careful evaluation. Location and radiation also help: a murmur heard best at the upper right chest may suggest aortic valve disease, while a murmur that radiates to the back in an infant might suggest a different pattern.

A useful patient perspective is this: hearing “murmur” can feel alarming, but in many cases it is a normal variant. The decision point is whether the murmur behaves like a typical innocent murmur and whether the person has symptoms or risk factors that change the likelihood of structural disease. The safest approach is a structured evaluation rather than guessing based on the sound alone.

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Common causes and risk factors by age

The most common causes of heart murmurs differ by age and clinical context. Thinking in age-based “buckets” helps you understand what your clinician is trying to rule in or out.

In infants and children, many murmurs are innocent. Common innocent patterns include:

  • Still’s murmur: often musical or vibratory; heard best at the lower left chest; common in school-aged children.
  • Pulmonary flow murmur: a soft systolic murmur near the upper left chest.
  • Venous hum: a continuous sound caused by blood flow in neck veins; often changes with head position.

However, murmurs in newborns get extra attention because early congenital heart disease can be subtle. Structural causes clinicians consider in babies include:

  • Valve narrowing (such as pulmonary or aortic stenosis)
  • Holes between chambers (atrial or ventricular septal defects)
  • Outflow tract abnormalities
  • Persistent fetal circulation pathways that should close after birth

Risk factors in children that raise suspicion for a structural cause include:

  • A family history of congenital heart disease or cardiomyopathy
  • Known genetic syndromes
  • Poor growth, feeding difficulty, or sweating with feeds in infants
  • Low oxygen levels on routine screening
  • Prior severe infections affecting the heart

In adults, a new murmur is more likely to be related to valves or heart muscle changes. Common causes include:

  • Aortic stenosis: often from age-related calcification; can cause exertional chest pressure, fainting, or breathlessness.
  • Mitral regurgitation: a leaky mitral valve; may cause fatigue, breathlessness, or palpitations.
  • Atrial fibrillation-related changes: can worsen valve leakage or make murmurs easier to hear.
  • Hypertrophic cardiomyopathy: thickened heart muscle that can create a murmur, especially with certain maneuvers.

Risk factors in adults include older age, high blood pressure, high cholesterol, diabetes, long-term smoking, prior rheumatic fever, prior heart attack, and a history of heart infection. A history of intravenous drug use or a recent bloodstream infection can raise concern for infective endocarditis, which may produce a new murmur.

Finally, some murmurs come from “high-flow” states where the heart is structurally normal but blood flow is faster:

  • Pregnancy
  • Fever or severe infection
  • Significant anemia
  • Overactive thyroid

This category matters because treating the trigger (iron deficiency, infection, thyroid disease) may reduce or eliminate the murmur without any heart procedure. In short: the same sound can mean very different things depending on age, symptoms, and context, which is why personalized evaluation is essential.

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Symptoms and red flags you shouldn’t ignore

Many people with a heart murmur have no symptoms at all. The murmur is found incidentally during a routine exam, sports physical, pregnancy visit, or pre-operative check. When symptoms are present, they usually come from the underlying cause—such as valve disease, a rhythm disorder, or heart failure—rather than from the murmur itself.

Symptoms that can occur with clinically significant causes include:

  • Shortness of breath during activity or when lying flat
  • Chest pressure, especially with exertion
  • Palpitations or an irregular heartbeat sensation
  • Dizziness, lightheadedness, or fainting
  • Swelling in legs or abdomen
  • Reduced exercise capacity and unusual fatigue

In infants and young children, symptoms can look different and may include:

  • Poor feeding, tiring quickly while feeding, or sweating with feeds
  • Rapid breathing, flaring nostrils, or chest retractions
  • Bluish lips or tongue (low oxygen)
  • Poor weight gain or failure to thrive
  • Excessive sleepiness or unusual irritability

Red flags that should prompt urgent medical assessment (same day or emergency care depending on severity):

  • Fainting, near-fainting, or collapse during exercise
  • Chest pain with exertion, especially with sweating or nausea
  • Severe shortness of breath at rest, or rapidly worsening breathing
  • New bluish discoloration of lips or skin
  • A newborn with a murmur plus feeding difficulty, fast breathing, or low oxygen readings
  • Fever with a new murmur, especially if accompanied by chills, unexplained fatigue, or signs of infection elsewhere
  • A murmur paired with very high blood pressure, uncontrolled thyroid symptoms, or severe anemia signs (extreme fatigue, pallor)

A practical nuance: “mild” symptoms can still matter if they show a new pattern. For example, someone who used to walk 2 km easily but now needs to stop every few minutes for breath deserves evaluation, even if they are not acutely ill. Similarly, in older adults, dizziness or falls may be the first clue to significant aortic stenosis.

It also helps to know which murmur patterns are more likely to be benign:

  • Soft, short systolic murmur
  • No symptoms
  • Normal growth and activity tolerance in children
  • No abnormal findings on exam (normal pulses, normal oxygen levels, no signs of heart enlargement)

And which patterns are more concerning:

  • Any diastolic murmur
  • Very loud murmurs (especially with a vibration you can feel)
  • Murmurs associated with abnormal pulses, abnormal blood pressure patterns, or signs of heart failure

If you are unsure, treat uncertainty as a reason to seek assessment—not as a reason to wait. A timely exam and targeted testing can usually clarify risk quickly.

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How a heart murmur is evaluated and diagnosed

Evaluation starts with a careful history and a detailed listening exam. Clinicians are not only listening for a sound—they are building a probability estimate: “Does this behave like an innocent murmur, or does it suggest structural heart disease?”

Key history questions often include:

  • When was the murmur first noticed?
  • Are there symptoms with exertion, feeding, or lying flat?
  • Any fainting, chest pain, palpitations, or swelling?
  • Recent fever, dental infection, or bloodstream infection?
  • Family history of congenital heart disease, early valve disease, or cardiomyopathy?
  • Pregnancy, anemia symptoms, thyroid symptoms, or stimulant use?

The physical exam often checks far beyond the stethoscope:

  • Blood pressure in both arms when relevant
  • Pulse quality and timing (including delayed pulses in some valve diseases)
  • Signs of fluid overload (leg swelling, lung crackles)
  • Oxygen saturation in infants and sometimes in symptomatic adults
  • Growth curves and feeding pattern in children

Clinicians describe murmurs using a structured set of features:

  • Timing (systolic, diastolic, continuous)
  • Intensity (grade)
  • Location (where it is loudest)
  • Radiation (to the neck, back, or armpit)
  • Pitch and quality (blowing, harsh, rumbling)
  • Response to maneuvers (standing, squatting, Valsalva, inspiration)

Maneuvers can provide strong clues. For example, some innocent murmurs soften when standing, while certain obstructive murmurs can become louder with decreased blood return to the heart (such as when standing suddenly). These patterns help decide who needs imaging promptly.

The most common confirmatory test is an echocardiogram (heart ultrasound). It can show valve narrowing or leakage, chamber sizes, pumping function, abnormal connections, and pressure estimates. In many cases, it provides a clear answer and helps guide follow-up timing.

Other tests may be added based on the suspected cause:

  • Electrocardiogram (ECG): rhythm problems, prior heart strain, or chamber enlargement clues
  • Chest X-ray: heart size and lung fluid patterns in symptomatic patients
  • Blood tests: anemia evaluation, thyroid function, kidney function, infection markers when endocarditis is a concern
  • Exercise testing: when symptoms occur with exertion or to assess functional limits safely
  • Advanced imaging: selected cases use cardiac MRI or CT for detailed anatomy

Referral decisions are often risk-based:

  • Newborns with murmurs are commonly referred because early assessment is challenging and the stakes are higher.
  • Any diastolic murmur or symptomatic murmur warrants prompt evaluation.
  • Clearly innocent murmurs in healthy, asymptomatic older children may not need echocardiography, but they should be rechecked if symptoms develop or the murmur changes.

A good evaluation ends with clarity: what the murmur likely represents, what testing is needed (if any), what the follow-up plan is, and which symptoms should trigger a sooner visit.

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Treatment options based on the underlying cause

Because a murmur is a sign, treatment depends entirely on what is causing it. Many murmurs require no treatment at all. Others are early warning signals that allow timely intervention before complications develop.

If the murmur is innocent or due to a temporary high-flow state
Management is often reassurance plus addressing triggers:

  • No medication or restrictions are needed for an innocent murmur.
  • If anemia is contributing, treating iron deficiency can reduce turbulence.
  • If fever or thyroid overactivity is driving a flow murmur, treating the underlying condition often reduces the murmur.

In these cases, the most important “treatment” is education. Patients and parents benefit from understanding what changes should prompt re-evaluation, such as new symptoms, a clear change in exercise tolerance, or new episodes of fainting.

If the murmur is caused by valve disease
Valve problems can be mild and stable for years or can progress and require intervention. Treatment may include:

  • Monitoring: periodic echocardiograms to track severity and heart chamber changes.
  • Symptom treatment: diuretics for congestion, blood pressure management, and rhythm control when atrial fibrillation is present.
  • Definitive procedures: valve repair or replacement when severity crosses evidence-based thresholds or symptoms develop. Options may include catheter-based procedures in selected patients, or surgery.

The timing of valve intervention is often based on a combination of:

  • symptom burden,
  • valve measurements on echocardiogram,
  • impact on heart size and function,
  • exercise testing results when symptoms are unclear, and
  • overall surgical or procedural risk.

If the murmur is caused by a congenital heart defect
Many small defects in children are monitored and may close or remain stable without causing harm. Others require specialist care and, occasionally, catheter-based closure or surgery. Treatment goals focus on normal growth, normal oxygen delivery, and protecting the heart from long-term strain.

If the murmur is linked to cardiomyopathy or obstructive patterns
Treatment may include:

  • medications to reduce obstruction, slow heart rate, or improve filling,
  • avoidance of dehydration and certain stimulant substances,
  • rhythm monitoring,
  • and specialist guidance on safe sports participation.

If endocarditis is a concern
A new murmur with persistent fever or signs of infection can require urgent evaluation. Treatment typically involves intravenous antibiotics, and sometimes valve surgery if damage is severe. Preventive antibiotics before dental procedures are recommended only for certain high-risk heart conditions, not for most people with murmurs.

What patients can expect after a cause is identified:

  • A clear severity label (mild/moderate/severe if valve disease is present)
  • A follow-up schedule that matches risk, not anxiety
  • Guidance on activity, pregnancy planning when relevant, and medication interactions
  • A plan for symptom changes that outlines when to call, when to be seen, and when to seek emergency care

The most empowering message is that “we found a murmur” often leads to “we found it early.” Early detection gives you options and time—two things that improve outcomes in many structural heart conditions.

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Living with a murmur, follow-up, and when to seek care

Living with a murmur is usually about living with good information. Once the cause is clarified, most people fall into one of three tracks: no follow-up needed, periodic monitoring, or active treatment.

If your murmur is innocent

  • You can usually exercise normally and live without restrictions.
  • You typically do not need repeat scans unless symptoms appear.
  • It can help to keep a brief note in your records stating that the murmur was evaluated and considered innocent, especially for school forms, sports clearance, or future medical visits.

If your murmur is linked to mild structural disease
Your clinician may recommend periodic follow-up to watch for progression. Helpful habits include:

  • Keep a record of your last echocardiogram date and the key finding (for example, “mild aortic stenosis”).
  • Track symptoms that signal a change: reduced exercise tolerance, new breathlessness, palpitations, swelling, or dizziness.
  • Maintain heart-healthy basics that reduce strain on valves and muscle: blood pressure control, cholesterol management, avoiding smoking, and regular activity appropriate to your condition.

If your murmur is linked to moderate or severe disease
Daily management often focuses on reducing stress on the heart and avoiding preventable flare-ups:

  • Take prescribed medications consistently and ask what each is for.
  • Ask whether you need antibiotics before certain procedures (many people do not, even with valve disease).
  • Discuss pregnancy planning early if you have significant valve disease or cardiomyopathy.
  • Learn your “action thresholds,” such as how much new swelling or weight gain should prompt a call.

Preparing for appointments can improve care quality. Consider bringing:

  • a medication list (including over-the-counter medicines),
  • blood pressure and heart rate logs if you have them,
  • a symptom timeline with dates,
  • and a family history summary.

When to seek care quickly
Contact a clinician promptly for:

  • new breathlessness, especially if it limits daily activities,
  • new palpitations, especially with dizziness,
  • swelling that is new or worsening,
  • chest discomfort with exertion,
  • new murmur identified during pregnancy.

Seek emergency care for:

  • fainting or near-fainting, especially during activity,
  • chest pressure with sweating, nausea, or severe shortness of breath,
  • severe breathing difficulty at rest,
  • bluish lips or severe weakness,
  • a newborn with poor feeding and fast breathing.

Finally, many people underestimate how much reassurance comes from a clear plan. If you leave a visit still wondering “Is this dangerous?” ask directly. A well-managed murmur—whether innocent or structural—should come with a practical roadmap: what it is, what to watch for, when to follow up, and what to do if things change.

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References

Disclaimer

This article is for general education and is not a substitute for personal medical care. A heart murmur is a physical exam finding with many possible causes, ranging from harmless normal variants to serious valve or heart muscle disease. If you have chest pain or pressure, fainting, severe shortness of breath, bluish lips, or a newborn with feeding or breathing difficulty, seek emergency care immediately. Do not start, stop, or change prescription medicines based on this article; diagnosis and treatment decisions should be made with a licensed clinician who can evaluate your symptoms, exam findings, and test results.

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