Heart murmurs are unusual or extra sounds heard during a heartbeat, typically detected through a stethoscope. The classic “lub-dub” sound is the noise made by your four heart valves closing in a perfectly coordinated sequence.

• The first sound, “lub,” is the sound of the mitral and tricuspid valves closing as the heart’s lower chambers (ventricles) begin to pump blood out.
• The second sound, “dub,” is the sound of the aortic and pulmonary valves closing after the blood has been ejected, preventing it from flowing backward.

A heart murmur is an additional sound like whooshing or swishing, and caused by turbulent blood flow.

Think of it like water flowing through a garden hose. When the hose is straight and open, the water flows silently. However, if you put a kink in the hose or place your thumb over the end to narrow the opening, the water rushes through turbulently, creating a distinct “whooshing” sound. A heart murmur is the same principle applied to your heart. It is the audible sound of blood flowing in a turbulent, rather than a smooth and silent, manner through the heart’s chambers and valves.

The most important thing to know about heart murmurs is that they fall into two main categories:

1. Innocent Murmurs (also called Functional or Physiologic Murmurs): These are by far the most common type. It is the sound of normal blood flowing through a structurally normal, healthy heart. The sound is present simply because the blood is moving rapidly enough to be heard by a stethoscope. These murmurs are harmless and do not represent any form of heart disease.
2. Pathological Murmurs (or Abnormal Murmurs): These murmurs are a sign of an underlying structural problem within the heart. The turbulence is caused by blood flowing through a narrowed or leaky valve, a hole between heart chambers, or another anatomical defect.

In my experience, many patients are frightened when they first hear the term “heart murmur,” but I always reassure them that not all murmurs are dangerous, in fact, many are entirely harmless and never cause symptoms.

The cause of a heart murmur depends entirely on whether it is innocent or pathological.

Causes of Innocent Murmurs

In an innocent murmur, the heart itself is completely normal. The sound is simply caused by blood flowing more rapidly than usual through the heart’s chambers and valves. This can happen in several situations:

• Childhood and Rapid Growth: Innocent murmurs are extremely common in healthy children and adolescents. Their hearts are beating faster, and their bodies are growing rapidly, leading to increased blood flow.
• Pregnancy: A pregnant woman’s blood volume increases significantly to support the growing baby, causing blood to flow more forcefully through the heart.
• Fever: A fever increases the body’s metabolic rate and heart rate, which can create a temporary murmur.
• Anemia: A low red blood cell count means the blood is thinner and must be pumped faster to deliver enough oxygen, which can cause turbulence.
• Hyperthyroidism: An overactive thyroid gland speeds up the body’s metabolism and heart rate.
• Physical Exertion: A temporary murmur can even be heard in a healthy athlete whose heart is pumping a large volume of blood during intense exercise.

Causes of Pathological Murmurs

An abnormal murmur is a sign that something is structurally wrong with the heart, forcing blood to flow through an abnormal pathway or a defective valve. Common causes include:

• Valvular Heart Disease: Problems with the heart’s four valves are a leading cause of pathological murmurs.
  • Stenosis (Narrowing): The valve leaflets are stiff or fused and cannot open fully. This forces blood to squirt through a smaller-than-normal opening, creating turbulence. Common examples are aortic stenosis and mitral stenosis.
  • Regurgitation or Insufficiency (Leaking): The valve does not close tightly, allowing blood to leak backward across the closed valve. Common examples are mitral regurgitation and aortic regurgitation.
• Congenital Heart Defects (Present at Birth):
  • Septal Defects: A hole in the septum (the wall separating the chambers of the heart). An Atrial Septal Defect (ASD) is a hole between the two upper chambers, and a Ventricular Septal Defect (VSD) is a hole between the two lower chambers.
  • Patent Ductus Arteriosus (PDA): A persistent opening between the aorta and the pulmonary artery that normally closes after birth.
• Other Structural Problems:
  • Hypertrophic Cardiomyopathy: A genetic condition where the heart muscle becomes abnormally thick, which can obstruct blood flow out of the heart.
  • Infective Endocarditis: A serious infection of the heart’s lining or valves. The infection can cause growths (vegetations) on the valve leaflets, damaging them and causing a new or changed murmur.

Clinically, I always listen for characteristics like pitch, timing, and location of the murmur. It helps distinguish between harmless flow sounds and something that requires a deeper look.

You can be born with a murmur (congenital), or develop one over time due to changes in heart function, illness, or lifestyle.

• Innocent murmurs have no risk factors. They are a normal physiological finding in many healthy people, especially children.
• Pathological murmurs are caused by heart disease, so the risk factors are those associated with developing heart problems. These can include:
  • A family history of heart defects or genetic conditions like hypertrophic cardiomyopathy.
  • A history of rheumatic fever remains a significant cause of valvular heart disease in many parts of the world.
  • A history of infective endocarditis or being at high risk for it (such as through intravenous drug use).
  • Age-related risk factors for degenerative valve disease, such as uncontrolled high blood pressure, high cholesterol, and diabetes.
  • Certain genetic syndromes, like Marfan syndrome or Down syndrome, are associated with heart defects.

I often explain to patients that murmurs aren’t “caught” like infections, they result from structural or functional changes in the heart’s anatomy or blood flow.

Many heart murmurs, especially innocent ones don’t cause any symptoms and are only discovered during a routine exam. However, if the murmur is due to an underlying problem, there may be warning signs.

• Innocent Heart Murmurs: By definition, an innocent murmur has no other signs or symptoms. The person is completely healthy, with no history of heart problems and no other physical signs of cardiac distress.
• Pathological Heart Murmurs: The murmur itself does not cause symptoms. Rather, the symptoms are caused by the underlying heart problem that is creating the murmur. These “red flag” symptoms indicate that the heart may be struggling:

In Infants and Young Children:

• A bluish tinge to the skin, lips, or nail beds (cyanosis).
• Poor feeding or difficulty gaining weight (failure to thrive).
• Rapid or labored breathing.
• Excessive sweating during feeding.

In Older Children and Adults:

• Shortness of breath, especially with physical activity or when lying down.
• Chronic cough.
• Chest pain.
• Dizziness or fainting spells (syncope).
• Swelling (edema) in the legs, ankles, or abdomen.
• Palpitations (a sensation of a rapid or irregular heartbeat).
• Enlarged neck veins.

Patients often tell me they felt fine until one day they noticed they couldn’t climb stairs without gasping. That kind of change may signal a murmur worth investigating.

The first step in identifying a murmur is listening to the heart with a stethoscope. The timing, pitch, and location of the sound help guide the next steps.

The Art of Listening (Auscultation)

An experienced doctor can learn a lot just by listening to the murmur with a stethoscope. They characterize the murmur based on several features:

• Timing: Does it occur when the heart is pumping (a systolic murmur) or when it is relaxing (a diastolic murmur)?
• Loudness: Murmurs are graded on a scale of 1 (very faint) to 6 (extremely loud).
• Pitch and Quality: Is it high-pitched or low-pitched? Is the sound harsh, blowing, rumbling, or musical?
• Location: Where on the chest is the murmur heard most clearly? This can correspond to the location of a specific valve.
• Changes with Position: An innocent murmur may change in loudness or even disappear when a person changes position (e.g., from lying down to standing).

Based on these characteristics, a doctor can often make a confident judgment about whether a murmur is likely innocent or pathological.

I reassure patients that hearing a murmur is just the first clue, we rely on imaging and blood work to truly understand what’s going on.

The Definitive Test: Echocardiogram

If there is any suspicion that a murmur is abnormal, the doctor will order an echocardiogram which is the gold standard test. An echocardiogram is a non-invasive ultrasound of the heart. This test can definitively:

• Identify a leaky or narrowed valve.
• Detects a hole between heart chambers.
• Measure heart muscle size and thickness.
• Assess the overall pumping function of the heart.

Other tests, such as an electrocardiogram (ECG) or a chest X-ray, may also be used to provide additional information about the heart’s rhythm and size.

The treatment plan depends entirely on the cause of the murmur.

Treatment for Innocent Murmurs

Innocent heart murmurs are harmless and require no treatment. The most important “treatment” is reassurance from the doctor that the heart is normal and healthy.

Treatment for Pathological Murmurs

The treatment plan is highly individualized based on the specific problem and its severity.

• Watchful Waiting: For mild valve problems or small septal defects that are not causing symptoms or straining the heart, the best course of action may be regular monitoring with follow-up echocardiograms.
• Medications: While medications cannot fix a structural problem like a faulty valve, they can be used to manage the symptoms and reduce the workload on the heart.
• Surgical or Catheter-Based Procedures: For severe or symptomatic conditions, a procedure may be necessary to fix the underlying problem. This can include:
  • Valve surgery to repair or replace a faulty heart valve.
  • Procedures to close a hole in the heart, which can sometimes be done with a catheter-based device or may require open-heart surgery.

I’ve seen patients go from fearful to relieved after a simple valve repair, they realize that modern treatments can drastically improve quality of life.

Hearing that you or your child has a heart murmur can be an unnerving experience, but it is essential to remember that a murmur is just a sound, not a disease. The vast majority of heart murmurs, particularly those found in healthy, active children, are innocent, the simple sound of blood flowing through a normal heart. For those whose murmur does signal an underlying issue, it serves as a valuable early clue, allowing doctors to diagnose and manage a heart condition before it becomes more serious. If a heart murmur is detected, the key is a proper evaluation. Patients often say the diagnosis gave them anxiety, but with a clear plan, education, and follow-up, they regained confidence and peace of mind.

American Heart Association. (2023). What is a heart murmur? Retrieved from https://www.heart.org/en/health-topics/heart-valve-problems-and-disease/heart-valve-problems-and-causes/what-is-a-heart-murmur

Mayo Clinic. (2022). Heart murmurs. Retrieved from https://www.mayoclinic.org/diseases-conditions/heart-murmurs/symptoms-causes/syc-20373171

National Heart, Lung, and Blood Institute (NHLBI). (2022). Heart murmur. Retrieved from https://www.nhlbi.nih.gov/health/heart-murmur