Heart murmurs are surprisingly common. Around 10 percent of adults and 40–50 percent of children have them, and Yale Medicine estimates that up to 75 percent of kids will experience a murmur at some point in childhood. Many are harmless and temporary, but some can signal a deeper heart issue.
In adults, a murmur may indicate hypertrophic cardiomyopathy (HCM)—a genetic condition where the heart muscle thickens and becomes stiff. Left untreated, HCM can be life-threatening. But it’s important to remember: not every heart murmur means you have HCM.
Below, we break down what murmurs are, their connection to HCM, and how doctors diagnose and treat them.
Your heart has four valves that regulate blood flow, opening and closing with each heartbeat. A normal heartbeat sounds like a steady “lub-dub.” A heart murmur is an extra sound—often described as a whooshing or swishing—caused by turbulent blood flow.
Innocent murmurs (common in kids) usually disappear by adulthood and aren’t dangerous.
Abnormal murmurs often indicate valve problems, congenital defects, or conditions like HCM.
In adults, murmurs typically mean something is affecting the structure or function of the heart.
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Not all murmurs are due to HCM, but most people with HCM have murmurs. That’s because the disease changes how blood flows out of the heart.
In HCM, the thickened heart muscle often blocks the left ventricular outflow tract (LVOT)—the pathway blood uses to exit the heart. This narrowing creates turbulence, which doctors hear as a murmur. About two-thirds of people with HCM have this obstructive type.
Think of it like water rushing through a garden hose: if you pinch the hose, the water comes out faster and noisier. That’s what happens inside the heart with LVOT obstruction.
HCM can also affect the mitral valve, which regulates blood flow between the left atrium and left ventricle. Thickened heart muscle can push the valve’s flaps into the LVOT, worsening the blockage and intensifying the murmur.
About one-third of HCM patients have non-obstructive HCM, meaning blood flow isn’t blocked, and murmurs may not be present. In rare forms, like apical HCM (where thickening occurs at the bottom of the heart), murmurs are also less likely.
Not all murmurs are linked to HCM. Other possible causes include:
Congenital heart defects (structural problems present at birth)
Endocarditis (infection of the heart lining or valves)
Heart valve disease (e.g., mitral valve regurgitation)
Anemia, fever, or hyperthyroidism (which speed up blood flow and create turbulence)
Often, murmurs are first discovered during a routine physical. If a doctor suspects HCM, they may test how the murmur changes under different conditions:
Valsalva maneuver (breathing technique) makes HCM murmurs louder.
Squatting can make them quieter.
Further tests may include:
Echocardiogram (ultrasound of the heart)
Electrocardiogram (ECG) (measures electrical activity and muscle thickness)
Chest X-ray (shows structural changes)
Because HCM is genetic, doctors may recommend genetic testing. Identifying gene mutations not only helps confirm diagnosis but also alerts family members who may be at risk—even if they don’t yet have symptoms.
RELATED: HCM: Why Genetic Testing Matters — Especially for Black Patients
Treatment focuses on managing HCM itself, which usually improves murmurs. Options include:
Beta-blockers and calcium channel blockers (ease the heart’s workload)
Myosin inhibitors (new drugs like Camzyos that directly target HCM’s cause)
Septal myectomy (surgical removal of thickened muscle)
Septal ablation (minimally invasive procedure to shrink muscle with alcohol injection)
Stay well-hydrated to ease blood flow.
Exercise under medical supervision (HCM patients are at risk for arrhythmias).
Some may need an implantable cardioverter defibrillator (ICD) to prevent sudden cardiac arrest.
1. Are all heart murmurs dangerous?
No. Many murmurs are harmless, especially in children. However, adult murmurs usually need further evaluation.
2. Can you have HCM without a murmur?
Yes. Non-obstructive and apical HCM often don’t produce murmurs.
3. What does an HCM murmur sound like?
Doctors describe it as a harsh, “whooshing” sound that changes with posture or breathing maneuvers.
4. Should I be worried if my doctor hears a murmur?
Not necessarily. It may be innocent, but your doctor will likely order tests to rule out serious conditions.
5. Can lifestyle changes help with HCM?
Yes. Staying hydrated, avoiding extreme exertion, and working closely with a cardiologist are key steps.
6. Is HCM hereditary?
Yes. If you’re diagnosed, family members should consider screening or genetic testing.
Bottom line: If you or a loved one has a heart murmur, don’t panic—but don’t ignore it either. Talk to your doctor, ask about testing, and stay proactive about your heart health.
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