The heart has four chambers. The upper two chambers are the right and left atrium. They're divided by a wall of tissue, the atrial septum.

Your child was born with a heart problem called an atrial septal defect (ASD). In an ASD, there's an opening in the wall (septum), which means some blood flows in the wrong direction. If the ASD is large, this can make the heart and lungs work harder over time.

A small ASD may not need treatment. A larger ASD will need surgery or a procedure to close it. Your cardiologist (heart specialist) will help you get the right treatment for your child. With the right care and follow-up, most children with an ASD live active, healthy lives.

Follow your cardiologist's instructions for:

• Giving any medicines to your child
• Feeding your child (Babies with larger ASDs may need to have smaller, more frequent feedings or need extra calories to grow.)
• Scheduling all follow-up appointments

Support your child's overall well-being by helping them:

• Be physically active every day. Ask your cardiologist if there are any activities your child needs to avoid.
• Get all recommended vaccines (shots).
• Brush their teeth twice a day, floss every day, and go for routine dental appointments. Check with your care team if your child needs to take antibiotics before going to the dentist.

Your child has signs that extra blood is going through the ASD to the lungs, such as:

• Fast breathing
• Not gaining weight or growing as expected
• Tiring more easily than expected
• Not feeding well (for babies)
• Swelling of the legs, feet, or belly
• Dizziness or near fainting
• Frequent colds or coughs
• Irregular or “fluttering” heartbeat

Your child:

• Has blue lips or skin that sucks in between their ribs when they're breathing
• Isn't drinking at all or has signs of dehydration (not enough water in the body), such as a dry or sticky mouth, sunken eyes, less pee or darker pee than usual, little or no tears when crying, or unusual sleepiness
• Faints

Why does an ASD happen? An ASD is a condition your child is born with. It happens when the opening in the atrial septum does not fully close during early development before birth. There's not always a clear cause, but an ASD can be caused by certain gene changes (mutations).

How does a large ASD change blood flow in the heart? Blood flows through the ASD into the right atrium, then into the right ventricle (the lower chamber of the heart), and out to the lungs. This extra blood flowing into the lungs makes the heart and lungs work harder. Over time, it can lead to lung infections and damage, irregular heartbeats, poor feeding in a baby, and other problems.

What other problems can happen? An ASD can let a blood clot go to the brain instead of going to the lungs first (where the blood clot gets filtered out). If that happens, the blood clot can block blood flow in the brain and cause a stroke.

Will my child have a heart murmur? A heart murmur is an extra noise that blood makes when flowing through the heart. Healthcare providers can hear a heart murmur when listening to the heart with a stethoscope. People with an ASD usually have a heart murmur.

What tests or procedures might my child need for an ASD? Your child's cardiologist may order:

• Chest X-ray
• Electrocardiogram (EKG), a test that measures the heart's electrical activity to show how it's working
• Echocardiogram or “echo,” an ultrasound (medical imaging scan) to take pictures of the heart
• Heart catheterization, a procedure in which a catheter (a thin, soft plastic tube) is put into a blood vessel in the arm or leg, then threaded to the heart. The catheter takes measurements and pictures to help the cardiologist better understand what's going on in the heart.

How is an ASD treated? A small ASD may not need treatment. If needed, the ASD can be fixed with catheterization or surgery:

• For catheterization, the catheter is used to carry a small device to the heart to plug the hole. Over time, the heart tissue grows around the device, holding it in place.
• For surgery, the surgeon closes the hole (by sewing it or putting a patch on it).