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For more information, visit http://www.nhlbi.nih.gov/health/health-topics/topics/heartmurmur/


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. Sometimes they 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

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

Innocent heart murmurs aren't caused by heart problems. These murmurs are common in healthy children. Many children will have heart murmurs heard by their doctors at some point in their lives.

People who have abnormal heart murmurs may have signs or symptoms of heart problems. Most abnormal murmurs in children are caused by congenital (kon-JEN-ih-tal) heart defects. These defects are problems with the heart's structure that are present at birth.

In adults, abnormal heart murmurs most often are caused by acquired heart valve disease. This is heart valve disease that develops as the result of another condition. Infections, diseases, and aging can cause heart valve disease.

Outlook

A heart murmur isn't a disease, and most murmurs are harmless. Innocent murmurs don't cause symptoms. Having one doesn't require you to limit your physical activity or do anything else special. Although you may have an innocent murmur throughout your life, you won't need treatment for it.

The outlook and treatment for abnormal heart murmurs depend 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. The left side of the heart receives the oxygen-rich blood from the lungs and pumps it to the body.

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

A Healthy Heart Cross-Section

Figure 1 shows the location of the heart in the body. Figure B shows a cross-section of a healthy heart and its inside structures. The blue arrow shows the direction in which oxygen-poor blood flows through the heart to the lungs. The red arrow shows the direction in which oxygen-rich blood flows from the lungs into the heart and then out to the body.

Figure 1 shows the location of the heart in the body. Figure B shows a cross-section of a healthy heart and its inside structures. The blue arrow shows the direction in which oxygen-poor blood flows through the heart to the lungs. The red arrow shows the direction in which oxygen-rich blood flows from the lungs into the heart and then out to 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 flows 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. The artery carries blood from the heart 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. This artery carries blood from the heart 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. 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 the 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 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 from the left side of the heart 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 to the body.
  • The superior and inferior vena cavae are large veins that carry oxygen-poor blood from the body back to the heart.

For more information about how a healthy heart works, go to the Health Topics 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 a Heart Murmur

Innocent Heart Murmurs

  • Benign heart murmurs.
  • Flow murmurs.
  • Functional heart murmurs.
  • Mammary souffle (SOO-fl). (This type of heart murmur is heard in some pregnant women because of increased blood flow to the breasts.)
  • Normal heart murmurs.
  • Physiologic heart murmurs.
  • Still's murmurs.
  • Venous hums.

Abnormal Heart Murmurs

  • Pathologic heart murmurs.



What Causes Heart Murmurs?

Innocent Heart Murmurs

Why some people have innocent heart murmurs and others do not isn't known. Innocent murmurs are simply sounds made by blood flowing through the heart's chambers and valves, or through blood vessels near the heart.

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. This is because during pregnancy, women's bodies make extra blood. Most heart murmurs that occur in pregnant women are innocent.

Abnormal Heart Murmurs

Congenital heart defects or acquired heart valve disease often are the cause of abnormal heart murmurs.

Congenital Heart Defects

Congenital heart defects are the most common cause of abnormal heart murmurs in children. These defects are problems with the heart's structure that are present at birth. They change the normal flow of blood through the heart.

Congenital heart defects can involve the interior walls of the heart, the valves inside the heart, or the arteries and veins that carry blood to and from the heart. Some babies are born with more than one heart defect.

Heart valve problems, septal defects (also called holes in the heart), and diseases of the heart muscle such as hypertrophic cardiomyopathy are common heart defects that cause abnormal heart murmurs.

Examples of valve problems are 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. A hole in the septum between the heart's two lower chambers is called a ventricular septal defect.

Hypertrophic (hi-per-TROF-ik) cardiomyopathy (kar-de-o-mi-OP-ah-thee) (HCM) occurs if heart muscle cells enlarge and cause the walls of the ventricles (usually the left ventricle) to thicken. The thickening may block blood flow out of the ventricle. If a blockage occurs, the ventricle must work hard to pump blood to the body. HCM also can affect the heart’s mitral valve, causing blood to leak backward through the valve.

Heart Defects That Can Cause Abnormal Heart Murmurs

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

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

For more information, go to the Health Topics Congenital Heart Defects article.

Acquired Heart Valve Disease

Acquired heart valve disease often is the cause of abnormal heart murmurs in adults. This is heart valve disease that develops as the result of another condition.

Many conditions can cause heart valve disease. Examples include heart conditions and other disorders, age-related changes, rheumatic (ru-MAT-ik) fever, and infections.

Heart conditions and other disorders. Certain conditions can stretch and distort the heart valves, such as:

Damage and scar tissue from a heart attack or injury to the heart.

Advanced high blood pressure and heart failure. These conditions can enlarge the heart or its main arteries.

Age-related changes. As you get older, calcium deposits or other deposits may form on your heart valves. These deposits stiffen and thicken the valve flaps and limit blood flow. This stiffening and thickening of the valve is called sclerosis (skle-RO-sis).

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 you have an untreated or not fully treated streptococcal (strep) infection.

Rheumatic fever can damage and scar the heart valves. The symptoms of this heart valve damage often don't occur until many years after recovery from rheumatic fever.

Today, most people who have strep infections are treated with antibiotics before rheumatic fever develops. It's very important to take all of the antibiotics your doctor prescribes for strep throat, even if you feel better before the medicine is gone.

Infections. Common germs that enter the bloodstream and get carried to the heart can sometimes infect the inner surface of the heart, including the heart valves. This rare but sometimes life-threatening infection is called infective endocarditis (EN-do-kar-DI-tis), or IE.

IE is more likely to develop in people who already have abnormal blood flow through a heart valve because of heart valve disease. The abnormal blood flow causes blood clots to form on the surface of the valve. The blood clots make it easier for germs to attach to and infect the valve.

IE can worsen existing heart valve disease.

Other Causes

Some heart murmurs occur because of an illness outside of the heart. The heart is normal, but an illness or condition can cause blood flow that's faster than normal. Examples of this type of illness include fever, anemia (uh-NEE-me-eh), and hyperthyroidism.

Anemia is a condition in which the body has a lower than normal number of red blood cells. Hyperthyroidism is a condition in which the body has too much thyroid hormone.




What Are the Signs and Symptoms of a Heart Murmur?

People who have innocent (harmless) heart murmurs don't have any signs or symptoms other than the murmur itself. This is because innocent heart murmurs aren't caused by heart problems.

People who have abnormal heart murmurs may have signs or symptoms of the heart problems causing the murmurs. These signs and symptoms may include:

  • Poor eating and failure to grow normally (in infants)
  • Shortness of breath, which may occur only with physical exertion
  • Excessive sweating with minimal or no exertion
  • Chest pain
  • Dizziness or fainting
  • A bluish color on the skin, especially on the fingertips and lips
  • Chronic cough
  • Swelling or sudden weight gain
  • Enlarged liver
  • Enlarged neck veins

Signs and symptoms depend on the problem causing the heart murmur and its severity.




How Is a Heart Murmur Diagnosed?

Doctors use a stethoscope to listen to heart sounds and hear heart murmurs. They may detect heart murmurs during routine checkups or while checking for another condition.

If a congenital heart defect causes a murmur, it's often heard at birth or during infancy. Abnormal heart murmurs caused by other heart problems can be heard in patients of any age.

Specialists Involved

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

Cardiologists are doctors who specialize in diagnosing and treating heart problems in adults. Pediatric cardiologists specialize in diagnosing and treating heart problems in children.

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. 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. For example, your doctor may look for a bluish color on your skin. In infants, doctors may look for delayed growth and feeding problems.
  • Ask about your symptoms, such as chest pain, shortness of breath (especially with physical exertion), dizziness, or fainting.

Evaluating Heart Murmurs

When evaluating a heart murmur, your doctor will pay 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.
  • 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 a change in body position affects the sound.

Diagnostic Tests and Procedures

If your doctor thinks you or your child has an abnormal heart murmur, he or she may recommend 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, lungs, and blood vessels. 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 heart's electrical activity. An EKG shows how fast the heart is beating and its rhythm (steady or irregular). 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), or echo, is a painless test that uses sound waves to create pictures of your heart. The test shows the size and shape of your heart and how well your heart's chambers and valves are working.

Echo also can show areas of poor blood flow to the heart, areas of heart muscle that aren't contracting normally, and previous injury to the heart muscle caused by poor blood flow.

There are several types of echo, including a stress echo. This test is done both before and after a stress test. During this test, you exercise to make your heart work hard and beat fast. If you can’t exercise, you may be given medicine to make your heart work hard and beat fast. Echo is used to take pictures of your heart before you exercise and as soon as you finish.

Stress echo shows whether you have decreased blood flow to your heart (a sign of coronary heart disease).




How Is a Heart Murmur Treated?

A heart murmur isn't a disease. It's an extra or unusual sound heard during the heartbeat. Thus, murmurs themselves don't require treatment. However, if an underlying condition is causing a heart murmur, your doctor may recommend treatment for that condition.

Innocent (Harmless) Heart Murmurs

Healthy children who have innocent (harmless) heart murmurs don't need treatment. Their heart murmurs aren't caused by heart problems or other conditions.

Pregnant women who have innocent heart murmurs due to extra blood volume also don't need treatment. Their heart murmurs should go away after pregnancy.

Abnormal Heart Murmurs

If you or your child has an abnormal heart murmur, your doctor will recommend treatment for the disease or condition causing the murmur.

Some medical conditions, such as anemia or hyperthyroidism, can cause heart murmurs that aren't related to heart disease. Treating these conditions should make the heart murmur go away.

If a congenital heart defect is causing a heart murmur, treatment will depend on the type and severity of the defect. Treatment may include medicines or surgery. For more information about treatments for congenital heart defects, go to the Health Topics Congenital Heart Defects article.

If acquired heart valve disease is causing a heart murmur, treatment usually will depend on the type, amount, and severity of the disease.

Currently, no medicines can cure heart valve disease. However, lifestyle changes and medicines can treat symptoms and help delay complications. Eventually, though, you may need surgery to repair or replace a faulty heart valve.

For more information about treatments for heart valve disease, go to the Health Topics Heart Valve Disease article.




Clinical Trials

The National Heart, Lung, and Blood Institute (NHLBI) is strongly committed to supporting research aimed at preventing and treating heart, lung, and blood diseases and conditions and sleep disorders.

NHLBI-supported research has led to many advances in medical knowledge and care. Often, these advances depend on the willingness of volunteers to take part in clinical trials.

Clinical trials test new ways to prevent, diagnose, or treat various diseases and conditions. For example, new treatments for a disease or condition (such as medicines, medical devices, surgeries, or procedures) are tested in volunteers who have the illness. Testing shows whether a treatment is safe and effective in humans before it is made available for widespread use.

By taking part in a clinical trial, you can gain access to new treatments before they're widely available. You also will have the support of a team of health care providers, who will likely monitor your health closely. Even if you don't directly benefit from the results of a clinical trial, the information gathered can help others and add to scientific knowledge.

If you volunteer for a clinical trial, the research will be explained to you in detail. You'll learn about treatments and tests you may receive, and the benefits and risks they may pose. You'll also be given a chance to ask questions about the research. This process is called informed consent.

If you agree to take part in the trial, you'll be asked to sign an informed consent form. This form is not a contract. You have the right to withdraw from a study at any time, for any reason. Also, you have the right to learn about new risks or findings that emerge during the trial.

For more information about clinical trials related to heart murmurs or other heart diseases or conditions, talk with your doctor. You also can visit the following Web sites to learn more about clinical research and to search for clinical trials:

For more information about clinical trials for children, visit the NHLBI's Children and Clinical Studies Web page.




Links to Other Information About Heart Murmurs

NHLBI Resources

Non-NHLBI Resources

Clinical Trials

 
September 20, 2012 Last Updated Icon

The NHLBI updates Health Topics articles on a biennial cycle based on a thorough review of research findings and new literature. The articles also are updated as needed if important new research is published. The date on each Health Topics article reflects when the content was originally posted or last revised.