What Is an Atrial Septal Defect?

Atrial septal defect or ASD for short, is a heart condition that can affect kids. To understand an atrial septal defect, it helps to know how the heart works. The heart has four chambers. The lower chambers of the heart are called the ventricles. There are two ventricles: a left ventricle and a right ventricle. The upper chambers are the atria and there are two of them — a left atrium and a right atrium.

You may already know that your heart is a muscle that pumps blood throughout your body. In a person without a heart defect, blood that's low in oxygen flows first to the right atrium, then to the right ventricle, and is then pumped to the lungs to receive oxygen.

The red oxygen-rich blood then returns to the left atrium, flows from there into the left ventricle, and heads out to the body through the aorta, a large blood vessel that carries blood from the heart to the smaller blood vessels in the body.

Between the right and left atria is a wall called the septum. In a person with an atrial septal defect, there's an opening in that wall. This hole in the wall lets oxygen-rich blood from the left atrium mix with oxygen-poor blood on the other side.

Many kids with an atrial septal defect don't have any problems or symptoms because of it. Occasionally, a kid with a very large atrial septal defect might have a poor appetite, may tire easily, may grow slowly, can experience shortness of breath, or have lung problems, like pneumonia.

Atrial Septal Defect Is One of the More Common Heart Defects

About 1 in every 100 babies is born with some type of heart defect. Atrial septal defects are one of the more common types of these heart defects. A person could be diagnosed with an atrial septal defect in infancy, childhood, during their teen years, or even as an adult.

In some kids with small-siz​ed atrial septal defects (small-siz​e holes), the hole can close up on its own. Most kids with a medium-siz​ed or large-siz​ed atrial septal defect will need some kind of procedure to close the hole. If the hole is left open, later in life that person may develop other kinds of heart problems, such as an abnormal heartbeat. The person also could develop serious damage to the lung blood vessels. The risk of having a stroke, a problem where a clot or air bubble clogs up a blood vessel in the brain, is also increased in someone with an atrial septal defect. To prevent these problems, doctors often recommend closing the hole while the kid is still young.

What Causes an Atrial Septal Defect?

Atrial septal defects develop when a baby is still growing inside its mother. Before birth, the heart begins as a large tube that folds and divides into sections that will become the walls and chambers of the baby's heart. If a problem occurs during this process, a hole may develop in the wall between the left atrium and right atrium.

In some cases, the tendency to develop an atrial septal defect may be inherited, or genetic. In other cases, an atrial septal defect might happen if the pregnant woman was exposed to chemicals while the baby was growing in her uterus. For most kids with atrial septal defects, no one knows why they developed this problem.

What Do Doctors Do?

Kids who have atrial septal defects may first find out that they have a heart murmur when examined by their doctor. The next stop is usually to a pediatric cardiologist, a doctor who specializes in diagnosing and treating heart disease in kids and teens.

The pediatric cardiologist will ask about the kid's medical history (the mother's health during pregnancy and illnesses the kid has had). The cardiologist also will do an exam and listen to the kid's heart. If a doctor thinks a kid may have an atrial septal defect, some tests might be done.

In some kids, the doctor may recommend regular follow-up visits to see if a small defect will close on its own. A kid with a small atrial septal defect usually can participate in sports and regular activities.

What If The Hole Doesn't Close on Its Own?

If the hole needs to be closed, the doctor will decide whether the kid needs surgery or a cardiac catheterization. In surgery, the doctor repairs the hole with stitches or a patch made out of either surgical material or the body's own tissue. A kid may have to spend a few days in the hospital after surgery. Within about 6 months, the tissue of the heart heals over the patch or stitches.

Another way to fix the hole is cardiac catheterization. This method uses a thin, flexible tube called a catheter. The cardiologist inserts the catheter into a blood vessel in the leg that leads to the heart. The cardiologist then guides the tube into the heart and inserts a device that covers the hole. The device is made out of metal mesh and is springy and flexible. The kid usually will spend a night at the hospital after the procedure. Over time the heart's tissue will grow to completely cover the device.

Kids who have had surgery or cardiac catheterization will need to follow their doctors' instructions for a while. But after just a few weeks, kids can return to their normal activities. Kids with atrial septal defects rarely have any further heart problems.