What is a heart murmur?

A heart murmur is a sound made by the flow of blood through the heart.  Blood flow through large blood vessels may also make a sound that is called a "heart murmur"  when the sound is heard with a stethoscope over the chest area. 

What causes a heart murmur?

Nearly ALL newborns are born with a heart murmur.  This is due to normal transition from the fetal circulation to the newborn circulation.  As the newborn breathes for the first time, the lungs replace the placenta as the source of oxygen.  The connection between the upper heart chambers (the atria), the connection between the aorta and the pulmonary artery and the vessels that supply the placenta are no longer needed.  As these connections close, blood flow through the openings make noise.  These connections typically close completely within a few days (or sooner).

Most children with heart murmurs have normal hearts.  The major blood vessels and branches are narrower and have sharper turns in children when compared to adults.  Just as water through a garden hose makes a noise when it is bent, blood flow through a narrow or bending blood vessel can make a noise.

Heart murmurs are more noticeable when blood flows through the heart with more force.  This can occur when a child is sick, has a fever, or is anemic.

A "vibratory" or "musical" murmur is heard when blood causes the heart valve cords to vibrate.  This is the most common type of heart murmur in children and is completely harmless.

When is a heart murmur a sign of something bad?

Some heart murmurs are not normal.  Pediatricians are trained to determine when a heart murmur should be evaluated with other tests.  Some warning signs of an abnormal murmur include the following:

• Cyanosis (blue discoloration of the skin)
• Breathing difficulties
• Poor feeding
• Poor growth
• Loud, harsh heart murmurs
• Heart murmurs combined with other abnormalities or deformities
• Heart murmurs with syndromes (i.e., Down syndrome)
• Abnormal heart rate, blood pressure, or blood oxygen levels

How can a heart murmur be evaluated further?

Occasionally, your physician may decide to do further testing such as:

Chest x-ray - shows the size of the heart, the general shape of the heart (heart silohuette), and can be used to estimate the degree of blood flow through the lungs.

Electrocardiogram (a.k.a., EKG, EKG) - shows heart rhythm abnormalities and pattern of electrical flow through the heart.

Echocardiogram - an ultrasound of the heart that shows detailed images of the heart shape, heart chambers, heart walls, blood flow direction and speed.

Other imaging tests such as CT scans or MRI's are sometimes performed.

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