Heart Murmurs in Children

Physicians rate heart murmurs on a scale of 1 to 6, based on their audibility.

Doctors classify heart murmurs into two categories:  innocent and abnormal.  Heart murmurs are extra sounds, such as whooshing or swishing, heard during a person’s heartbeat cycle.  Turbulent blood in and around the heart causes the extra sounds known as a heart murmur.  Over 50 percent of all children will have a heart murmur, most of which are harmless, at some time during their lives.

The Normal Heartbeat Cycle

To understand what the pediatrician hears when a heart murmur is present, you must first understand how the heart works.  The heart is made up of four chambers and four valves.  The two upper chambers are the atria (singular – atrium) and the two lower chambers are called ventricles.  During a heartbeat cycle, blood fills the atrium on the right with low-oxygen blood.  From here, the blood passes through the tricuspid valve to the right ventricle.  This ventricle pumps the blood through the pulmonary valve to the lungs for oxygenation.  The newly oxygenated blood returns from the lungs to the left upper chamber, called the left atrium where it passes across the mitral valve to the left ventricle.  The left ventricle pumps it across the aortic valve where the aorta pumps it to all parts of the body.

The Sound of a Murmur

The heart valves closing as the heart pumps the blood to the various places results in the familiar lub-DUB sound commonly associated with a normal heartbeat.  Any extra sound the pediatrician hears, such as lub-da-DUB or other sound constitutes a heart murmur.

Diagnosing a Heart Murmur

Physicians rate heart murmurs on a scale of 1 to 6 based on their audibility.  A heart murmur rated at 1 is barely audible and a murmur rated at 6 is loud and easily heard.  The pediatrician will listen to several areas of your child’s chest and note where he hears the murmur best.  He will also record other characteristics, such as whether the murmur is a soft whooshing or a harsh, high frequency sound and where he hears it in the heartbeat cycle.  Depending on this assessment, the pediatrician will decide whether to refer your child to a pediatric cardiologist for further evaluation.  Many parents mistakenly believe that all heart murmurs are serious.  To avoid overreaction and unnecessary anguish, you should know the type of murmur your child has and whether it is cause for concern.

Innocent Murmurs

Innocent or functional murmurs are the most common type heard in children.  Those with innocent murmurs have normal hearts with no defects.  Newborns and young children commonly have innocent heart murmurs.  Blood flowing through the heart more rapidly than normal can produce the sounds associated with this type of murmur. With this diagnosis, your child will not need to limit physical activity or restrict normal activities because of the murmur.  Innocent murmurs usually disappear, as the child grows older, and rarely pose a health threat.

Abnormal Murmurs

Some murmurs can indicate a structural heart problem, such as a congenital heart defect.  If the doctor believes your child may have an abnormal heart murmur, he will refer you to a pediatric cardiologist.  The cardiologist may order chest X-rays, an electrocardiogram (EKG), or an echocardiogram.  An echocardiogram produces ultrasound images of the heart structures and can record the blood motion, speed, and direction as it flows through the heart structures.  Symptoms of a congenital heart problem in infants include cyanosis (blue color in lips), rapid breathing, feeding issues, and general failure to thrive.  For older children or adolescents symptoms may include chest pain, difficulty participating in physical activity, and chronic fatigue.

Common Types of Structural Defects

Septal Defects

These defects involve the septa, or walls, between the upper or lower chambers.  With this disorder, the septum contains a hole, allowing blood to leak between the chambers and causing a murmur.  A tiny hole may close on its own.  Larger holes will need closure by surgery.

Valve Defects

Defective valves may be too narrow, too small, or have some other type of structural problem.  These structural issues may allow blood back flow or inhibit the smooth flow of blood, causing turbulent flow across the valve among other issues.  Valve defects can often be corrected through surgery.


Cardiomyopathy refers to defects of the heart muscle itself.  Patients with cardiomyopathy have heart muscle that is too thick or weak to effectively pump blood to all parts of the body.

A Heart Murmur Is Not a Disease

When the pediatric physician diagnoses your child with a heart murmur, it is not a disease.  Your child may have an innocent murmur, meaning that his heart is healthy and working properly.  If your child has an abnormal murmur, the pediatric cardiologist will discuss the best options available to correct the problem.


Photo credit: livestrong dot com

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  1. #1 by Rodney Hindle on February 8, 2011 - 6:19 PM

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