If you press your ear against someone’s chest, you’ll expect to hear the typical “lub-dub” sound of their heart beating; it’s the noise that a heart makes when it’s pumping blood. 

But if a person has a heart murmur, doctors hear something different when they place a stethoscope on their chest. Instead, mixed in with the heartbeat sounds, they hear extra swooshing noises, which is the sound of blood moving through the heart. Sometimes, the swooshing noise is a sign that there may be a heart-valve problem or a structural defect within the heart—and sometimes they are what doctors may call “innocent,” or harmless.  

Heart murmurs may be diagnosed in people of all ages, including newborns and children. In fact, by some estimates heart murmurs are heard in up to 75% of children at some point in their childhood. Only about 1% of are actually born with heart defects. Therefore, the vast majority of murmurs in children are innocent and have no significance. They are a normal finding and do not represent a heart problem. You are just hearing blood flow through a healthy heart.  

Adults may develop a heart murmur at any time, if one of the four valves within the heart begins to malfunction. Doctors can determine the location of a heart murmur by listening with a stethoscope and performing tests; each heart-valve problem has its own location and signature sound pattern.  

For innocent heart murmurs, no treatment is needed. For abnormal heart murmurs, the type of treatment that’s needed varies, depending on the location and cause of the problem. 

“The most important test for a heart murmur is a careful exam with a stethoscope,” says cardiologist John Fahey, MD, director of Yale Medicine’s Adult Congenital Heart Program. “If your doctor determines that the murmur is innocent, no further testing is needed. You may participate in all activities with no concerns or restrictions.”

When blood is pumped through the heart’s chambers, it makes a distinct noise that’s often described as “lub-dub.” The heart makes the “lub” sound when two of its valves close, after blood moves from the first two heart chambers to the two other chambers. The “dub” sound occurs when the heart’s two other valves shut, after blood is pumped out of the heart.  

A heart murmur is an extra, unexpected sound that doctors hear with a stethoscope when they’re listening to the blood move through the heart. Some heart murmurs are incidental noises within healthy hearts, and they aren’t a sign of a problem. Other murmurs are indications that a structural abnormality exists within the heart, causing problems with blood flow. They may occur if the valves don’t open or close properly, preventing the blood from moving through the heart to maintain its usual “lub-dub” rhythm.  

While many heart murmurs will cause no problems, that’s not true for all. Sometimes, an abnormal heart murmur is a sign that there is a hole in a wall within the heart. More frequently, a murmur is a sign that a heart valve is malfunctioning, causing blood-flow problems.

When a heart murmur is harmless, a doctor can hear the sound of blood flowing through the heart with a stethoscope, but there is no structural abnormality causing the noise. These harmless, murmurs are more commonly detected among children, in pregnant women, and in people who are thin, but it’s possible for anyone to be diagnosed with a harmless murmur at any age.  

An abnormal heart murmur may be a sign of a congenital defect, present at birth, or a problem may have developed later in life. The location and volume of the sound, as well as its length and timing, may help a doctor figure out what may be causing the murmur.  

Possible problems include:  

• Leaky heart valve. Heart valves that function properly close tightly at a designated time during the heartbeat cycle, which keeps blood moving forward through the heart. Sometimes, a heart valve becomes damaged and doesn’t shut entirely. When this happens, some blood may leak backwards through the valve, when it should have moved forward. The sound of the blood swooshing backwards creates a murmur sound.
• Narrowed heart valve. Properly functioning heart valves open fully at the correct time to allow blood to move through the heart. If a heart valve becomes stiff and narrow over time, it won’t open fully when the blood is supposed to pass through and it will obstruct blood flow. It may take longer for the blood to pass through the valve, and more pressure may be needed to move it forward. The sound of the blood moving more forcefully through a narrow opening for a longer time frame than usual creates an abnormal heart murmur. This condition is more common among older adults, who are more likely to have hardened blood vessels and heart valves.
• Hole in the heart wall. Occasionally, a baby is born with a hole in a wall between two heart chambers, and adults may develop such a hole after a heart attack or surgery. If blood is leaking through an abnormal opening between heart chambers, it can lead to shortness of breath or other symptoms. The abnormal blood-flow pattern also causes a heart murmur.
• Certain infectious diseases. Sometimes, bacterial endocarditis—an infection of the heart’s inner lining—may cause a heart murmur. Rheumatic fever—an infection that’s related to strep throat, which is very rare in the U.S.—may cause damage to heart valves, possibly leading to a murmur.     

Innocent heart murmurs have no symptoms. People with abnormal heart murmurs may experience such symptoms as:

• Trouble breathing
• Shortness of breath
• Sweating
• Chest pain
• Fainting
• Skin with a bluish tint
• Weight gain
• Neck veins that bulge
• A chronic cough 

Babies and young children with abnormal heart murmurs may also experience:

• Feeding problems
• Excessive fussiness
• Poor growth
• Fast breathing

Certain conditions may increase the risk of heart murmurs:

• Being born with a heart defect, such as a hole in a heart wall
• A family history of heart defects or heart murmurs
• Having had bacterial endocarditis or rheumatic fever
• Heart-valve problems
• Intravenous drug use

When a doctor hears abnormal heart sounds with a stethoscope, they may suspect a heart murmur. To better assess the situation, he or she may ask the person to hold their breath or change positions. This is because some heart murmurs become more or less pronounced when a person is breathing versus holding their breath or squatting versus standing.  

The doctor will also ask about a personal or family history of heart murmurs or structural heart defects, as well as whether there is a personal history of any symptoms that may accompany an abnormal heart murmur.  

If there is any reason to suspect a heart murmur may be abnormal, one or more tests will be used to diagnose the condition. These may include:

• Electrocardiogram, which measures electrical activity within the heart and can determine where the abnormal activity may be located
• Echocardiogram, which is an ultrasound exam that produces images of the heart, its valves and the adjoining blood vessels
• Chest X-ray
• MRI, which shows images of the structures within the heart
• Cardiac catheterization, an invasive exam in which a long, thin tube is inserted into a blood vessel and threaded toward the heart, where it can diagnose abnormalities; this is only done if other tests are inconclusive

When a heart murmur is found to be “innocent” or harmless, no treatment is needed. When a heart murmur is abnormal, the underlying health condition should be treated. Common treatments include:

• Anti-arrhythmic medications, which may help the heart return to a more normal rhythm
• ACE inhibitors or ARBs, which can help to lower blood-pressure levels in individuals with high blood pressure, sometimes also helpful for people with heart murmurs
• Blood thinners, which can lower the risk that a person with poorly functioning heart valves will develop blood clots in the heart
• Antibiotics, which treat bacterial infections that may cause a heart murmur
• Surgery or a cardiac catheterization, which can close a hole within a heart wall, or can repair or replace a heart valve

People with innocent heart murmurs don’t experience any complications from the condition. Most innocent heart murmurs in children disappear before adulthood.  

When someone has an abnormal heart murmur, the prognosis depends on the cause and severity of the problem. Many people only require monitoring by their doctors so long as their condition does not worsen; if it does, they are offered medication or surgery as needed to manage or improve their situations.

“Yale has been a leader and innovator in treating children and adults with heart defects since the 1940s,” says Dr. Fahey. “We carefully evaluate heart murmurs several times a day in our clinics and provide state-of-the-art workups and interventions for any and all patients when necessary.”