Hearing your baby’s doctor tell you that he detects a heart murmur likely sends immediate concerns through your mind. However, heart murmurs are quite common in babies, and many kids have one at some point. It’s not actually a disorder or illness, but a description of how the heart is operating. Usually it’s nothing to worry about, and it doesn’t affect the health of the child.
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The heart has four separate chambers, and four one-way valves attaching them. The two lower chambers pump, and they’re called ventricles. The two upper chambers accept incoming blood, and they’re called atria.
Blood that’s low in oxygen comes from the body into the right atrium, then goes through a valve into the right ventricle, and over to the lungs to get more oxygen. That oxygen-rich blood returns to the heart through the left atrium, then across a valve into the left ventricle. From there it’s pumped through the aorta, which is a large blood vessel, and on to smaller blood vessels throughout the body.
A heart murmur is the term used when an extra swishing sound is heard besides the normal heartbeat, which is the sound of the valves opening and closing. A doctor can hear these sounds with a stethoscope, but a child needs to sit very quietly for that to happen, because his heart is near his chest wall, and outside sounds can get picked up. You might be asked to hold your baby in your lap while the doctor listens, or calm him down; if he’s crying, it’s almost impossible to hear a murmur.
Although parents often fear the worse, not all heart murmurs are serious. They’re graded on scale from 1 to 6, where 1 is almost inaudible and 6 is quite loud. When your baby’s doctor hears it, he’ll note where in the heart it occurs, at what point in the heartbeat cycle, what type of sound it makes, and whether the noise changes when your child moves. If further evaluation is required, your child will be referred to a pediatric cardiologist.
Sometimes a heart murmur will be heard at one appointment, when it wasn’t noticed at the last one. This could be because heart murmurs are better heard when children are in certain positions or have a different heart rate. It could also mean it’s due to a heart problem that’s recently developed, or one that’s been there since birth but hasn't been severe enough to make a detectable murmur.
Innocent, or functional, heart murmurs are the most common kind, where the murmur isn’t associated with any health threat, and the heart is normal and healthy. If your baby has this type of murmur, it will come and go throughout his childhood, and will likely eventually go away on its own. There is no special treatment, diet or restrictions on activities.
Congenital Heart Defects
About 1 percent of babies are born with a congenital heart defect, and a heart murmur could be a sign of the problem. Your baby may or may not have any additional symptoms, and they could show up shortly after birth, or not until he’s older. If your baby’s doctor thinks the heart murmur is more than just an innocent murmur, your baby will be referred to a pediatric cardiologist for further tests. This might include a chest X-ray or echocardiogram (ECG), which is an ultrasound of the heart.
Other symptoms of heart disease in infants include blueness in the lips, rapid breathing, difficulties with feeding and failure to thrive.
Congenital heart defects can be inherited, linked to premature birth or disorders like Down syndrome, or caused by environmental factors such as exposure to industrial-strength chemicals. The mother’s health during pregnancy can also have an impact; pregnant women who get German measles, have poorly regulated diabetes or a body metabolism error called PKU have a higher chance of giving birth to a baby with a heart defect. A mother drinking alcohol during pregnancy, or a father using cocaine before conception, might also have an effect. However, congenital heart defects are often found in babies without any known risk factors.
Common Heart Defects
Structural defects, where holes are found in the heart and narrow valves, are the most common type of heart defect. Septal defects occur in the walls between the heart’s upper and lower chambers; a hole in the septum might allow blood to leak between chambers, meaning the heart has to work too hard and could get enlarged. Smaller holes repair themselves over time, but a larger hole might need surgery.
Valve abnormalities are common too, and occur when one of the heart’s valves is too narrow, too thick, too small, or blocked, so it doesn’t do its job of preventing the blood from flowing backwards. Balloon catheters can sometimes open the blocked valve without surgery; in other cases, an operation is required.
Heart muscle disorders, also called cardiomyopathy, can cause the heart muscle to be too thick or weak, and reduce the heart’s ability to pump blood normally.