What Is a Heart Murmur?

A heart murmur is an extra or unusual sound heard during a heartbeat. Murmurs range from very faint to very loud. They sometimes sound like a whooshing or swishing noise.

Normal heartbeats make a "lub-DUPP" or "lub-DUB" sound. This is the sound of the heart valves closing as blood moves through the heart. Doctors can hear these sounds and heart murmurs using a stethoscope.

Overview

There are two types of heart murmurs: innocent (harmless) and abnormal.

People who have innocent heart murmurs have normal hearts. They usually have no other signs or symptoms of heart problems. Innocent murmurs are common in healthy children. Many, if not most, children will have heart murmurs heard by their doctors at some time in their lives.

People who have abnormal murmurs may have other signs or symptoms of heart problems. Most abnormal murmurs in children are due to congenital heart defects. These are heart defects that are present at birth.

In adults, abnormal murmurs are most often due to heart valve problems caused by infection, disease, or aging.

Outlook

A heart murmur isn't a disease, and most murmurs are harmless. Innocent murmurs don’t cause symptoms or require you to limit physical activity. Although an innocent murmur may be a lifelong condition, your heart is normal and you likely won’t need treatment.

The outlook and treatment for abnormal heart murmurs depends on the type and severity of the heart problem causing them.

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 also are 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 How the Heart Works article. 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 murmurs
• Flow murmurs

Abnormal Heart Murmurs

• Pathologic heart murmurs

What Causes a Heart Murmur?

Innocent Heart Murmurs

Innocent heart murmurs are sounds heard when blood flows through a normal heart. These murmurs may occur when blood flows faster than normal through the heart and its attached blood vessels. Illnesses or conditions that may cause this to happen include fever, anemia (uh-NEE-me-eh), and hyperthyroidism (too much thyroid hormone in the body).

Extra blood flow through the heart also may cause innocent heart murmurs. After childhood, the most common cause of extra blood flow through the heart is pregnancy. Most heart murmurs found in pregnant women are innocent. They’re due to the extra blood that women's bodies make while they’re pregnant.

Changes to the heart that result from heart surgery or aging also may cause some innocent heart murmurs.

Abnormal Heart Murmurs

The most common cause of abnormal murmurs in children is congenital heart defects. These are problems with the heart’s structure that are present at birth.

These defects can involve the interior walls of the heart, the valves inside the heart, or the arteries and veins that carry blood to the heart or out to the body. Some babies are born with more than one heart defect. Congenital heart defects change the normal flow of blood through the heart.

Heart valve defects and septal defects (also called holes in the heart) are common heart defects that cause abnormal heart murmurs.

Valve defects may include narrow valves that limit blood flow or leaky valves that don’t close properly.

Septal defects are holes in the wall that separates the right and left sides of the heart. This wall is called the septum.

A hole in the septum between the heart’s two upper chambers is called an atrial septal defect (ASD). A hole in the septum between the heart’s two lower chambers is called a ventricular septal defect (VSD). ASDs and VSDs account for more than half of all abnormal heart murmurs in children.

Heart Defects That Can Cause Abnormal Heart Murmurs

Figure A shows the anatomy and blood flow of the inside of a normal heart. Figure B shows a heart with leaking and narrowed valves. Figure C shows a heart with a ventricular septal defect.

Conditions that damage heart valves or other structures of the heart also may cause abnormal heart murmurs. These include rheumatic (ru-MAT-ik) fever, endocarditis (EN-do-kar-DI-tis), calcification (KAL-si-fi-KA-shun), and mitral (MI-tral) valve prolapse (MVP). Heart murmurs due to these problems are more common in adults.

Rheumatic Fever

The bacteria that cause strep throat, scarlet fever, and, in some cases, impetigo (im-peh-TI-go) also can cause rheumatic fever. This serious illness can develop if a person has an untreated or not fully treated strep infection.

Rheumatic fever can lead to permanent heart damage. If you or your child has strep throat, take all of the antibiotics prescribed, even if you feel better before the medicine runs out.

Endocarditis

Endocarditis is a serious infection of the heart valves or lining of the heart. A bacterial infection usually causes endocarditis, and it usually occurs in an abnormal heart. Endocarditis can lead to permanent heart damage and other health problems.

Calcification

Calcification occurs when the heart’s valves get hard and thick as a result of aging. When this happens, the valves don’t work as they should.

Mitral Valve Prolapse

MVP is a condition in which the heart’s mitral valve doesn’t work properly. In MVP, when the left ventricle contracts, one or both flaps of the mitral valve flop or bulge back (prolapse) into the left atrium. This can cause a heart murmur.

What Are the Signs and Symptoms of a Heart Murmur?

Most people who have heart murmurs don’t have any other signs or symptoms of heart problems. These murmurs usually are innocent (harmless).

Some people who have heart murmurs do have signs or symptoms of heart problems. The signs and symptoms may include:

• Blue coloring of the skin, especially on the fingertips and inside the mouth
• Poor eating and abnormal growth (in infants)
• Shortness of breath
• Excessive sweating
• Chest pain
• Dizziness or fainting
• Fatigue (feeling very tired)

Signs and symptoms depend on the problem causing the murmur and how severe that problem is.

How Is a Heart Murmur Diagnosed?

Doctors use a stethoscope to listen to heart sounds and hear heart murmurs. They often notice innocent heart murmurs during routine checkups or physical exams.

Doctors also may find abnormal heart murmurs during routine checkups. When a congenital heart defect causes a murmur, it’s often heard at birth or during infancy. Abnormal murmurs caused by other heart problems can be heard in patients of any age.

Specialists Involved

Doctors usually refer people who have abnormal murmurs to cardiologists or pediatric cardiologists for further care and testing.

Cardiologists are doctors who treat adults who have heart problems. Pediatric cardiologists treat children who have heart problems.

Physical Exam

Your doctor will carefully listen to your heart or your child’s heart with a stethoscope to find out whether a murmur is innocent or abnormal. He or she will listen to the loudness, location, and timing of the murmur to classify and describe the sound. This will help your doctor diagnose the cause of the murmur.

Your doctor also may:

• Ask about your medical and family histories.
• Do a complete physical exam. He or she will look for signs of illness or physical problems. These may include blue coloring of the skin and delayed growth and feeding problems (in infants).
• Ask about your symptoms, such as chest pain, shortness of breath (especially with physical activity), dizziness, or fainting.

Evaluating Heart Murmurs

When evaluating a heart murmur, your doctor pays attention to many things, such as:

• How faint or loud the sound is. Your doctor will grade the murmur on a scale of 1 to 6 (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 also can be heard in the neck or back.
• Whether the sound has a high, medium, or low pitch.
• How long the sound lasts.
• How breathing, physical activity, or change of body position affects the sound.

Classifying Heart Murmurs

Doctors classify murmurs as systolic, diastolic, or continuous.

A systolic murmur is heard when the heart is squeezing and pumping blood out of the heart.

A diastolic murmur is heard when the heart is relaxing and filling with blood. Diastolic murmurs often are a sign of a heart defect or heart disease, and further checking is likely needed.

A continuous murmur is heard during the entire heartbeat. These murmurs often are a sign of a heart defect or heart disease, and further checking is likely needed.

Diagnostic Tests and Procedures

If your doctor suspects you or your child has an abnormal heart murmur, he or she may order one or more of the following tests.

Chest X Ray

A chest x ray is a painless test that creates pictures of the structures inside your chest, such as your heart and lungs. This test is done to find the cause of symptoms, such as shortness of breath and chest pain.

EKG

An EKG (electrocardiogram) is a simple test that detects and records the electrical activity of the heart. An EKG shows how fast the heart is beating, the heart’s rhythm (steady or irregular), and where in the body the heartbeat is being recorded.

An EKG also records the strength and timing of electrical signals as they pass through each part of the heart.

This test is used to detect and locate the source of heart problems. The results from an EKG also may be used to rule out certain heart problems.

Echocardiography

Echocardiography (EK-o-kar-de-OG-ra-fee) is a painless test that uses sound waves to create pictures of your heart. The test gives information about the size and shape of your heart and how well your heart’s chambers and valves are working.

The test also can find areas of heart muscle that aren’t contracting normally due to poor blood flow or injury from a previous heart attack.

There are several different types of echocardiography, including stress echocardiography. This type is done both before and after a cardiac stress test. During this test, you exercise or take medicine (given by your doctor) to make your heart work hard and beat fast. Stress echocardiography shows whether you have decreased blood flow to your heart (a sign of coronary artery disease).

Cardiac Catheterization

If your doctor thinks that your or your child’s abnormal heart murmur is due to a heart problem, such as a congenital heart defect, he or she may want you to have a procedure called cardiac catheterization (KATH-e-ter-i-ZA-shun).

For this procedure, a long, thin, flexible tube called a catheter is put into a blood vessel in your arm, upper thigh (groin), or neck and threaded to your heart. Through the catheter, your doctor can perform diagnostic tests and treatments on your heart.

How Is a Heart Murmur Treated?

Innocent Heart Murmurs

Healthy children who have innocent heart murmurs don’t need treatment because they have normal hearts. If your child has an innocent murmur, alert his or her doctor during regular checkups.

Pregnant women who have innocent heart murmurs due to extra blood volume also don’t need treatment.

You may have an innocent heart 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 Heart Murmurs

Treatment for abnormal heart murmurs depends on the heart problems causing them. For example, treatment for a congenital heart defect depends on the type and severity of the defect. Treatment may include medicine or surgery. (For more information, see the Diseases and Conditions Index Congenital Heart Defects article.)

When an infection or disease causes a heart murmur, treatment depends on the type, amount, and severity of the heart damage. Treatments may include medicine or surgery.

Key Points

• A heart murmur is an extra or unusual sound heart during a heartbeat. Murmurs range from very faint to very loud. They sometimes sound like a whooshing or swishing noise.
• There are two types of heart murmurs: innocent (harmless) and abnormal. A person who has 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. A person who has an abnormal murmur may have other signs or symptoms of a heart problem.
• A heart murmur is not a disease, and most murmurs are harmless. However, a murmur may be a sign of a heart problem, especially if other signs or symptoms are present.
• Innocent heart murmurs are sounds heard when blood flows through a normal heart. This may happen if blood flows faster than normal through the heart or if there’s extra blood flow through the heart. Changes to the heart that result from heart surgery or aging also may cause some innocent heart murmurs.
• The most common cause of abnormal heart murmurs in children is congenital heart defects. These are problems with the heart’s structure that are present at birth. Infections or other conditions that damage the heart valves or other structures of the heart also may cause abnormal heart murmurs. Heart murmurs due to these problems are more common in adults.
• Some people who have heart murmurs have signs and symptoms of heart problems. These may include a blue coloring of the skin, poor eating and abnormal growth (in infants), shortness of breath, excessive sweating, chest pain, dizziness or fainting, and fatigue (feeling very tired).
• Doctors use a stethoscope to listen to heart sounds and hear heart murmurs. To diagnose a heart murmur, your doctor may do a physical exam, ask about your medical and family histories, and ask about your symptoms. If your doctor suspects that you or your child has an abnormal heart murmur, he or she may order diagnostic tests.
• Many people who have innocent heart murmurs don’t need treatment. In some cases, an innocent heart murmur may be due to an illness or condition. The murmur will go away once the illness or condition is treated. Treatment for abnormal heart murmurs depends on the heart problem causing them. Treatments may include medicine or surgery.
• Innocent heart murmurs don’t cause symptoms or require you to limit physical activity. Although an innocent murmur may be a lifelong condition, your heart is normal and you likely don’t need treatment.
• If you have an abnormal heart murmur, the amount and type of ongoing care and treatment you will need depends on how severe your condition is. Talk to your doctor about the type of care you need.

Links to Other Information About Heart Murmurs

NHLBI Resources

• Congenital Heart Defects (Diseases and Conditions Index)
• Heart Valve Disease (Diseases and Conditions Index)
• Holes in the Heart (Diseases and Conditions Index)

Non-NHLBI Resources

• Congenital Heart Defects (MedlinePlus)
• Heart Murmur (MedlinePlus)
• Heart Valve Diseases (MedlinePlus)

Clinical Trials

• Current Research (ClinicalTrials.gov)