What is an enlarged heart? This is a question that comes up fairly often. Not infrequently a child is referred because a chest x-ray demonstrates an "enlarged heart". Likewise, I often hear from parents who tell me that they had a relative who was diagnosed with an enlarged heart. So what exactly does this mean?
The first point to note is that lay people frequently use the term “enlarged
heart” to refer to different things. Some of them use it to describe a
situation in which the heart muscle is thicker than normal. Others might use
it to describe a heart muscle which is dilated, in other words, the volume of
the heart is larger than normal. Finally, occasionally a situation in which
one of the arteries leaving the heart (eg the aorta) is enlarged may end up
being inaccurately labeled as an “enlarged heart”.
In cardiology the term enlarged heart typically describes a heart which is larger than normal in terms of volume or mass. The important questions to address are: 1) is the heart enlarged because of an increased volume, increased mass, or both? 2) which chamber or chambers are enlarged? and 3) what is the cause of the enlarged heart? Causes of an enlarged heart may range from normal variants all the way to life-threatening problems.
In some instances the heart may be thought to be enlarged but really isn't. This is occasionally seen in children referred for an enlarged heart on x-ray. The x-ray creates an image of the heart and lungs almost like creating a shadow on a wall. Sometimes variation in the position of the child or the depth of inspiration when the chest ray is taken can affect the appearance of the heart. In this situation, an echocardiogram can accurately determine the exact size of the heart. In some cases a child referred for an enlarged heart on x-ray actually ends up having a perfectly normal heart size when we look at it with an echocardiogram.
Likewise, sometimes an enlarged heart can be a normal variant. Athletic training causes an increase in heart volume and mass due to exercise. Just as athletic training builds other muscles in the body, it can also build the heart muscle. In this circumstance, a slightly enlarged heart may be a good thing! No one would consider a mildly enlarged heart from athletic training to be a problem!
Unfortunately, sometimes an enlarged heart is truly abnormal. The heart can enlarge from a number of different causes. In children, the most common reason is some form of congenital heart defect. For example, a hole in the heart (or some other abnormality) may allow blood to shunt or recirculate back to the lungs. Examples of shunts include a ventricular septal defect, atrial septal defect, and patent ductus arteriosus. In all of these examples, a communication exists which allows blood to recirculate to the lungs. This ends up sending more blood than normal to the lungs; subsequently more blood returns to back to the heart. The heart subsequently enlarges because of the extra volume delivered to it.
Some cases of enlarged hearts in children are caused by valve problems. Valves that don't open properly, or valves that leak can create an extra stress on the heart, resulting in enlargement. For example, many children with significant aortic valve regurgitation caused by a bicuspid aortic valve may develop enlargement of the left ventricle over time. This can be an indication for replacement of the valve.
Hypertrophic cardiomyopathy is a genetic heart muscle disorder which causes severe thickening of the heart muscle and subsequent enlargement do to excessive mass. Unfortunately this may often be clinically silent and therefore go undetected. Hypertrophic cardiomyopathy is the most common cause of sudden cardiac death in young athletes.
A final cause of an enlarged heart is any problem with the heart muscle in terms of its contractility or squeezing function. This is usually the cause of an enlarged heart in adults. It can also be seen in children but is less common. Example of an enlarged heart in this situation would include a cardiomyopathy, or heart muscle disease. In this setting, the heart muscle doesn't squeeze well and enlarges as a compensatory mechanism.
In summary, there are many causes of an enlarged heart in children, some of them potentially normal. Certainly if there is any suggestion of an enlarged heart in your child, make sure to check it out!
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