What Is a Heart Murmur?

A heart murmur is an extra or unusual sound heard during your heartbeat. Murmurs range from very faint to very loud and sometimes sound like a whooshing or swishing noise. Normal heartbeat sounds—"lub-DUPP" or "lub-DUB"—are the valves closing as blood moves through the heart. (Go to the How the Heart Works section for more information about how a normal heart works.)

A heart murmur is not a disease; it is a sound that the doctor hears with a stethoscope. It may be normal, or it could be a sign that something may be wrong. Most heart murmurs are harmless. Some are signs of heart problems, especially if other signs or symptoms of a heart problem are present.

Types of Murmurs

Innocent (harmless) murmurs

A person with an innocent murmur has a normal heart and usually has no other signs or symptoms of a heart problem. Innocent murmurs are common in healthy children.

Abnormal murmurs

A person with an abnormal murmur usually has other signs or symptoms of a heart problem. Most abnormal murmurs in children are due to congenital heart defects—heart defects present at birth. In adults, abnormal murmurs are most often due to heart valve problems caused by infection, disease, or aging.

How the Heart Works

The heart is a muscle about the size of your fist. It works like a pump and beats 100,000 times a day.

The heart has two sides, separated by an inner wall called the septum. The right side of the heart pumps blood to the lungs to pick up oxygen. Then, oxygen-rich blood returns from the lungs to the left side of the heart, and the left side pumps it to the body.

The heart has four chambers and four valves and is connected to various blood vessels. Veins are the blood vessels that carry blood from the body to the heart. Arteries are the blood vessels that carry blood away from the heart to the body.

A Healthy Heart Cross-Section

The illustration shows a cross-section of a healthy heart and its inside structures. The blue arrow shows the direction in which oxygen-poor blood flows from the body to the lungs. The red arrow shows the direction in which oxygen-rich blood flows from the lungs to the rest of the body.

Heart Chambers

The heart has four chambers or "rooms."

• The atria (AY-tree-uh) are the two upper chambers that collect blood as it comes into the heart.
• The ventricles (VEN-trih-kuls) are the two lower chambers that pump blood out of the heart to the lungs or other parts of the body.

Heart Valves

Four valves control the flow of blood from the atria to the ventricles and from the ventricles into the two large arteries connected to the heart.

• The tricuspid (tri-CUSS-pid) valve is in the right side of the heart, between the right atrium and the right ventricle.
• The pulmonary (PULL-mun-ary) valve is in the right side of the heart, between the right ventricle and the entrance to the pulmonary artery, which carries blood to the lungs.
• The mitral (MI-trul) valve is in the left side of the heart, between the left atrium and the left ventricle.
• The aortic (ay-OR-tik) valve is in the left side of the heart, between the left ventricle and the entrance to the aorta, the artery that carries blood to the body.

Valves are like doors that open and close. They open to allow blood to flow through to the next chamber or to one of the arteries, and then they shut to keep blood from flowing backward.

When the heart's valves open and close, they make a "lub-DUB" sound that a doctor can hear using a stethoscope.

• The first sound-the "lub"-is made by the mitral and tricuspid valves closing at the beginning of systole (SIS-toe-lee). Systole is when the ventricles contract, or squeeze, and pump blood out of the heart.
• The second sound-the "DUB"-is made by the aortic and pulmonary valves closing at beginning of diastole (di-AS-toe-lee). Diastole is when the ventricles relax and fill with blood pumped into them by the atria.

Arteries

The arteries are major blood vessels connected to your heart.

• The pulmonary artery carries blood pumped from the right side of the heart to the lungs to pick up a fresh supply of oxygen.
• The aorta is the main artery that carries oxygen-rich blood pumped from the left side of the heart out to the body.
• The coronary arteries are the other important arteries attached to the heart. They carry oxygen-rich blood from the aorta to the heart muscle, which must have its own blood supply to function.

Veins

The veins are also major blood vessels connected to your heart.

• The pulmonary veins carry oxygen-rich blood from the lungs to the left side of the heart so it can be pumped out to the body.
• The vena cava is a large vein that carries oxygen-poor blood from the body back to the heart.

For more information on how a healthy heart works, see the Diseases and Conditions Index article on How the Heart Works. This article contains animations that show how your heart pumps blood and how your heart's electrical system works.

Other Names for Heart Murmurs

Innocent Heart Murmurs

• Normal heart murmurs
• Benign heart murmurs
• Functional heart murmurs
• Physiologic heart murmurs
• Still's murmur
• Flow murmur

Abnormal Heart Murmurs

• Pathologic heart murmurs

What Causes Heart Murmurs?

Innocent Heart Murmurs

Innocent murmurs are heard when blood moves noisily through a normal heart. Sometimes these murmurs occur when:

• Blood is flowing faster than usual through the heart and blood vessels attached to the heart.
• An increased amount of blood is flowing through the heart.

Illnesses or conditions that can cause blood to flow faster than usual through the heart include:

• Fever
• Anemia
• Too much thyroid hormone in the body (hyperthyroidism)

Many, if not most, children will have a heart murmur heard by their doctor at some time in their lives. After childhood, the most common cause of an increased amount of blood flowing through the heart is pregnancy. Most murmurs found in pregnant women are innocent. They are due to the extra blood that women's bodies make while they are pregnant.

Innocent murmurs are sometimes due to changes to the heart resulting from heart surgery or from aging.

Abnormal Heart Murmurs

The most common cause of abnormal murmurs is congenital heart defects. Congenital heart defects occur when the heart, heart valves, or blood vessels attached to the heart do not develop normally before a baby is born. Some babies are born with a combination of heart defects. Common defects that cause murmurs include:

• Congenital septal defects, which are holes in the wall (septum) that separates the right and left sides of the heart. They account for more than half of abnormal murmurs in children.
• Congenital valve defects, which include narrow valves that do not allow enough blood to flow through them and leaking valves that do not close properly.

Figure A shows the normal anatomy and blood flow of the interior of the heart. Figure B shows a heart with a murmur caused by leaking and narrowed valves. Figure C shows a murmur caused by a ventricular septal defect. Please note that many heart murmurs occur in normal hearts and occur without underlying heart disease. These are known as innocent heart murmurs.

Infections and other conditions that damage heart valves or other structures of the heart also may cause murmurs. These include:

• Rheumatic fever, a serious illness that can develop after a person has an untreated or incompletely treated infection caused by the bacteria that cause strep throat or scarlet fever. Rheumatic fever can lead to permanent damage to the heart. If your doctor diagnoses strep throat, be sure your child takes all of the antibiotics prescribed, even if he or she feels better before the antibiotics run out.
• Endocarditis, an inflammation of the inner lining of the heart and valves that is usually caused by a bacterial infection. Endocarditis is a serious disease that can lead to permanent heart damage and other complications. Endocarditis usually occurs in an abnormal heart.
• Calcification (hardening and thickening) of valves as a result of aging. The hardened and thickened heart valves do not work as they should.

What Are the Signs and Symptoms of Heart Murmurs?

Most people with heart murmurs do not have any other signs and symptoms of a heart problem. The murmur is usually innocent (harmless).

Some people with heart murmurs do have signs and symptoms of a heart problem. The signs and symptoms may include:

• Blue coloring of the skin, especially on the fingertips and inside the mouth
• Poor eating and failure to grow normally (in infants)
• Fast breathing
• Excessive sweating
• Chest pain
• Dizziness
• Shortness of breath
• Fainting
• Fatigue (feeling very tired)

The signs and symptoms depend on the cause and the severity of the problem causing the murmur.

How Are Heart Murmurs Diagnosed?

Doctors use a stethoscope (STETH-uh-skope) to listen to heart sounds and hear murmurs. They often notice innocent heart murmurs during routine checkups or physical exams.

Doctors may also find abnormal murmurs during routine checkups. Murmurs caused by congenital heart defects are often heard at birth or during infancy. Doctors may hear murmurs caused by other heart problems at any age.

Doctors usually refer people with abnormal murmurs to a heart specialist (a pediatric cardiologist for children or a cardiologist for adults) for further evaluation and testing.

Physical Exam

Doctors listen carefully to the heart with a stethoscope to help decide if a murmur is innocent or abnormal. They listen to the loudness, location, and timing of the murmur to classify and describe the sound. This helps the doctor begin to diagnose the cause of the murmur.

The doctor also:

• Takes a medical and family history
• Does a complete physical exam, looking for signs of illness or physical problems (such as blue coloring of the skin, delayed growth, and feeding problems in an infant)
• Asks about symptoms, such as chest pain, shortness of breath (especially with exercise), dizziness, or fainting

Evaluation of Murmurs

When evaluating a heart murmur, the doctor pays attention to a number of things, including:

• How faint or loud the sound is. The doctor grades the murmur on a 1–6 scale (1 is very faint and 6 is very loud).
• When the sound occurs in the cycle of the heartbeat.
• Exactly where the sound is heard in the chest, and whether it can also be heard in the neck or back.
• Whether the sound has a high, medium, or low pitch.
• How long the sound lasts.
• How breathing, exercise, or change of body position affects the sound.

Classification of the Murmur

Doctors classify murmurs as:

• Systolic—heard when the heart is squeezing and pumping blood out of the heart.
• Diastolic—heard when the heart is relaxing and filling with blood. Diastolic murmurs are often a sign of a heart defect or heart disease and should be further evaluated.
• Continuous—heard during the entire heartbeat. These are often a sign of a heart defect or heart disease and should be further evaluated.

Tests

When doctors hear a murmur that might be abnormal, they order tests, such as:

• Chest x ray. A chest x ray takes a picture of your heart and lungs. It can show if the heart is enlarged, and it can show some problems of the heart and lungs.
• EKG (electrocardiogram). This test is used to measure the rate and regularity of your heartbeat. The EKG can help rule out a variety of heart problems.

A heart specialist—a pediatric cardiologist or a cardiologist—will most likely do the followup testing. These tests might include:

• Echocardiogram. This test uses sound waves to create a moving picture of your heart. Echocardiogram provides information about the size and shape of your heart and how well your heart chambers and valves are functioning. The test also can identify areas of poor blood flow to the heart, areas of heart muscle that are not contracting normally, and previous injury to the heart muscle caused by poor blood flow.
• There are several different types of echocardiograms, including a stress echocardiogram. During this test, an echocardiogram is done both before and after your heart is stressed either by having you exercise or by injecting a medicine into your bloodstream that makes your heart beat faster and work harder. A stress echocardiogram is usually done to find out if you have decreased blood flow to your heart (coronary artery disease).
• Cardiac catheterization and angiography. Cardiac catheterization is a procedure in which a thin, flexible tube (catheter) is passed through an artery or vein in your upper thigh (groin) or in your arm to reach the heart, after you are sedated. This allows measurement of pressure inside the heart and blood vessels. Angiography involves injecting a dye that can be seen by using x ray. This helps the doctor see the flow of blood through the heart and blood vessels.

How Are Heart Murmurs Treated?

Innocent Murmurs

Healthy children with innocent murmurs do not need treatment because they have a normal heart. If your child has an innocent murmur, alert your pediatrician during regular checkups. Pregnant women with innocent murmurs due to increased blood volume also do not need treatment.

If you have an innocent murmur due to an illness or condition such as anemia, hyperthyroidism, or fever, the murmur will go away once the illness or condition is treated.

Abnormal Murmurs

The treatment for heart problems that cause abnormal murmurs varies depending on the specific heart problem.

The treatment of congenital heart defects is based on the type and severity of the heart defect or defects causing the murmur. Treatment may include medicine or surgery. Children with congenital heart defects are treated by doctors who specialize in treating children's heart problems (pediatric cardiologists). See Congenital Heart Defects for more information.

The treatment of heart problems caused by infection or disease depends on the type and severity of the damage to the heart. The treatment may include medicine or surgery.

Key Points

• A heart murmur is an extra or unusual sound heard during your heartbeat. Murmurs range from very faint to very loud and sometimes sound like a whooshing or swishing noise.
• Most heart murmurs are harmless (innocent).
• Sometimes a heart murmur indicates a heart problem, especially if other signs or symptoms of a heart problem are present.
• Innocent, harmless murmurs are common in healthy children. A child or adult with an innocent murmur has a normal heart.
• Doctors listen carefully to the heart with a stethoscope to help decide if a murmur is innocent or abnormal.
• Doctors listen to the loudness, location, and timing of the murmur in order to classify and describe the sound.
• Most abnormal murmurs in children are due to congenital heart defects—heart defects present at birth.
• In adults, abnormal murmurs are most often due to heart valve problems caused by infection, disease, or aging.

Links to Other Information About Heart Murmurs

NHLBI Resources

• Congenital Heart Defects (Diseases and Conditions Index)

Non-NHLBI Resources

• Congenital Heart Disease (MedlinePlus)
• Heart Valve Diseases (MedlinePlus)

Clinical Trials

• Current Research (National Institutes of Health)