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Children's Health

heart murmur in 4 month old



is it possible to not have detected a heart murmur until a child is 4 months old? could moving to denver have any affect on just finding the murmur?


Heart murmurs are sounds that the blood flowing through the heart make.  Smooth flow is very quiet, while more turbulent (rough) flow is louder, the common example of this is a river - when the water is flowing slowly it is very quiet but rapids are louder.

In a newborn, the heart rate is very fast 140-160 beats per minute and then slows down.  Heart murmurs are heard between the heart beats so it can be more difficult to hear in a new born than a 4 month old.  It is also more difficult for some newborns to lie still which has typically improved by four months of age, also improving the physical exam ability.  Newborns also have many more cells (red blood cells) in their blood, which they needed in the uterus but no longer need once they are born, as this happens (normally and naturally) the heart has to work a little bit harder to get oxygen to the body.  When a heart beats harder the blood flows faster and more turbulently so a murmur can be heard.  Denver, the mile high city, is at an elevation (meaning slightly less oxygen in the air) which again, can make the heart work a little bit harder but we all adapt to altitude within a very short period of time.  Sometimes murmurs are a sign of other things going on within the heart, but those murmurs are typically heard at birth, are typically louder and tend to cause other physical problems like poor weight gain.

The issue to discuss with your child's primary care provider is what is necessary to do about the murmur.  Since you are asking the question without discussing other tests, it is very likely your child's primary care provider has determined this murmur to be an "innocent murmur" and as such is not considered to interfere with your child's health and should not cause you additional worry.  As I did not examine the child, I cannot provide that diagnosis as a medical fact, so please discuss the issue further with your child's primary care provider.

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Response by:

Michael Spigarelli, MD, PhD
Formerly, Associate Professor of Pediatrics and Internal Medicine
College of Medicine
University of Cincinnati