Understanding heart murmurs and why they occur

A routine annual physical ends with your doctor pausing mid-exam, listening a second time, then saying, "I'm hearing a slight murmur." Five seconds later, your mind is already running through everything you think you know about heart disease. For many people, this moment triggers real anxiety, but understanding what a murmur actually is and what it means can help you move forward with clarity rather than fear.

A heart murmur is an extra whooshing, swishing, or blowing sound heard during the heartbeat. Rather than the normal "lub-dub" sounds (called S1 and S2), a murmur happens when blood flows through the heart in a way that creates turbulence. Most murmurs picked up during a routine physical, especially in children and young adults, turn out to be innocent murmurs with no structural problem at all. According to Cleveland Clinic, the majority of murmurs found this way require no treatment and cause no complications over a lifetime.

Two broad categories exist. Innocent murmurs, also called functional or physiologic murmurs, occur when the heart is structurally normal but blood moves faster or more turbulently than usual. Pathologic murmurs, by contrast, signal an actual problem: a valve that's narrowed (stenosis), a valve that leaks (regurgitation), a hole between heart chambers (septal defect), or a thickened heart muscle. A murmur itself is a physical exam finding, not a diagnosis. Doctors grade murmurs on the Levine scale from I to VI, and timing, location, and follow-up testing determine what the murmur actually represents.

What is the difference between innocent and pathologic heart murmurs?

Innocent murmurs come from normal blood flow moving faster or more turbulently than usual. Fever, pregnancy, anemia, a growth spurt in children, or exercise can all trigger this pattern. The heart structure underneath is completely normal. Pathologic murmurs, by contrast, stem from an actual structural cause: valve stenosis, valve regurgitation, a hole between chambers, or a thickened heart muscle as in hypertrophic cardiomyopathy.

The Levine grading scale helps separate the two categories. Innocent murmurs are typically grade I or II out of VI (barely audible or soft), and they don't produce a palpable thrill, the vibration you'd feel if you placed a hand on the chest. Pathologic murmurs often grade III or louder and frequently come with a palpable thrill. Timing is a second major clue. Innocent murmurs are almost always systolic, falling between the first and second heart sounds (the "lub" and "dub"). Any diastolic murmur or murmur that runs continuously across the entire heartbeat is treated as pathologic until testing proves otherwise.

How can you tell if a heart murmur is innocent?

Several clinical clues point toward an innocent murmur. First, the volume: innocent murmurs are soft, grade I or II, without a palpable thrill. Second, the character and location. Still's murmur, the most common innocent murmur, has a distinctive musical or vibratory quality, sometimes described as a twanging string, heard best at the lower left sternal border. Third, how it changes with position and activity. Innocent murmurs often soften when you sit or stand, become more noticeable when lying down, and may increase with fever or right after exercise. Finally, symptoms are absent. A truly innocent murmur occurs without chest pain, shortness of breath, fainting, or reduced exercise tolerance.

"An innocent murmur is a harmless sound caused by blood flowing rapidly through an otherwise normal heart, and it doesn't require treatment."

— Mayo Clinic

What are the 4 types of heart murmurs?

Heart murmurs are classified by when they occur during the heartbeat and what causes them. Understanding each type helps your cardiologist narrow down whether you're dealing with an innocent murmur or one that warrants closer follow-up.

• Systolic murmurs occur between S1 and S2 during heart contraction. This is the most common category, including most innocent murmurs as well as pathologic conditions like mitral regurgitation or aortic stenosis.
• Diastolic murmurs happen between S2 and S1 while the heart relaxes and fills with blood. These are always considered pathologic, as seen with aortic regurgitation or mitral stenosis.
• Continuous murmurs span the entire cardiac cycle without a break, heard with conditions like a patent ductus arteriosus.
• Innocent (functional) murmurs form their own distinct category: normal-flow sounds such as Still's murmur or a venous hum that require no treatment or follow-up testing.

How murmurs relate to palpitations, heart rate, and heart failure

A normal resting heart rate for most adults falls between 60 and 100 beats per minute, according to Mayo Clinic. A murmur by itself doesn't change this range, though an underlying valve problem can push the heart to compensate with a faster rate. Heart palpitations, that fluttering, pounding, or skipped-beat sensation, can appear alongside a pathologic murmur when an irregular rhythm and structural valve issue occur together. Palpitations alone, however, don't confirm either condition.

In congestive heart failure, a new or worsening murmur often reflects valve regurgitation that develops as the heart's pumping efficiency declines. This is why clinicians track murmur changes over time rather than relying on a single reading. We covered this in our guide to irregular heart rhythms, which often run alongside murmur findings. For patients already managing heart failure, it's important to discuss any new supplement with your care team before starting it. Supplements like melatonin can interact with your heart rate and blood pressure control if you're on heart failure medications.

When should you worry about a heart murmur?

Several patterns flag a murmur for closer evaluation. A murmur first noticed in adulthood (new onset), rather than one heard throughout childhood, calls for assessment. A murmur graded III out of VI or louder carries more concern than a grade I or II. Any diastolic or continuous murmur requires follow-up, since these patterns typically point to pathology. Symptoms alongside a murmur demand prompt cardiology evaluation: chest pain, shortness of breath with routine activity, fainting, or swelling in the legs and ankles all signal the need for testing.

Context matters too. A family history of congenital heart disease or sudden cardiac death raises the priority for testing even when the murmur itself sounds mild. Long-standing coronary artery disease or high blood pressure can strain heart valves over time, making a previously stable murmur worth reassessing rather than assuming it's unchanged.

"A heart murmur that develops in adulthood, or one accompanied by chest pain, shortness of breath, or fainting, should be evaluated by a cardiologist promptly."

— Cleveland Clinic

Red-flag symptoms that prompt same-week evaluation include:

• New murmur detected after age 40
• Murmur grade III or louder with a palpable thrill
• Diastolic or continuous timing pattern
• Chest pain or pressure, especially with activity
• Shortness of breath during normal daily tasks
• Fainting, lightheadedness, or dizziness
• Leg or ankle swelling that worsens over time
• Family history of congenital heart disease or sudden cardiac death

Do you need an ECG or echocardiogram to evaluate a heart murmur?

An EKG, or electrocardiogram, records the heart's electrical activity, rate, and rhythm. It doesn't directly detect a murmur, since a murmur is a sound produced by blood flow, not an electrical signal. A normal EKG doesn't rule out a pathologic murmur. Its main role is identifying arrhythmias, such as atrial fibrillation, that sometimes accompany valve disease.

An echocardiogram, an ultrasound that uses color Doppler to visualize blood flow, is the definitive test. It shows valve structure and motion, measures chamber size, and quantifies the severity of regurgitation or stenosis. At BioSyntrx, the physical exam and Levine grading come first, with EKG and echocardiogram testing ordered when the murmur's characteristics or accompanying symptoms suggest a pathologic cause.

Heart-healthy habits that support long-term outcomes

If you've been found to have an innocent murmur, the good news is straightforward: your risk profile stays low with routine follow-up. But whether your murmur is innocent or requires treatment, these habits protect your long-term heart health and often catch new issues before they become serious.

• Keep up with routine physical exams. Auscultation during a yearly checkup is often how a new murmur is first identified, before symptoms appear. Early detection makes management clearer.
• Manage blood pressure and cholesterol proactively. Untreated high blood pressure and atherosclerosis add strain to heart valves and the vessels feeding them over time. Talk to your provider about targets that fit your risk profile.
• Aim for at least 150 minutes of moderate-intensity aerobic activity per week. According to the CDC, this volume of exercise supports normal heart rate and rhythm. Walking, cycling, and swimming all count.
• Discuss any supplement with your care team before starting. If you have an existing heart failure or arrhythmia diagnosis, ask about interactions. Work with your clinician to review your full medication and supplement list annually.
• Track your own symptoms. Note any new chest discomfort, shortness of breath, or palpitations, and report them at your next visit. You're the expert on what's normal for you.

For managing high blood pressure, work closely with your cardiologist or primary care provider to find medications and lifestyle adjustments that work for your situation. Consistency matters more than perfection.

Schedule a heart murmur evaluation with BioSyntrx Cardiology

The reassuring truth is that most murmurs turn out to be innocent. But only a hands-on exam and, when appropriate, follow-up testing can confirm that with confidence. If you've been told you have a murmur or you're managing an existing cardiac condition, a cardiology evaluation clarifies your actual risk and rules out surprises.

At BioSyntrx Medical Center in San Francisco, our cardiologists work as part of a coordinated multi-specialty team. That means if your murmur evaluation leads to findings related to high blood pressure, an arrhythmia, or another issue, you have access to expert care for all of it under one roof. We've built our practice on clear communication during every step, from the stethoscope exam to test results to your treatment plan.

Schedule your evaluation today. Your peace of mind is worth the clarity that comes from an accurate diagnosis and a plan built on evidence, not worry. Whether your murmur turns out to be innocent or requires ongoing care, you'll know exactly what you're working with and what comes next.