The atrial septum is the wall between the two upper chambers of the heart (right and left atria). An atrial septal defect (ASD) is an abnormal hole in this wall. ASD is a heart problem that is present at birth (congenital). ASDs are common and account for about 10% to 15% of congenital heart disease. The clinical significance is typically related to the location and size of the ASD.

ASDs can happen on their own. Or they can happen in children born with other congenital heart defects.

ASDs are classified by their different location and development:

• Secundum ASD. This occurs in the middle part of the atrial septum.
• Primum ASD. This occurs in the lower part of the atrial septum close to the tricuspid and mitral valves.
• Sinus venosus. This occurs in the upper part of the atrial septum near the veins that drain into the right and left atrium.
• Coronary sinus ASD. This occurs when there is a defect in the wall between the coronary sinus and the left atrium.

Patent foramen ovale (PFO) is an opening between the right and left atria that is normally present in fetal circulation. It typically closes shortly after birth. But a PFO is not considered an ASD because no septal tissue is missing.

The heart forms during the first eight weeks of pregnancy. It starts as a hollow tube and divides into four chambers. These chambers are separated by walls (septa). It's normal for the walls to have openings as the fetus grows. The openings usually close shortly before or just after birth. If they don't all close, the atrial septum will have a hole in it. This is called an ASD. ASDs are often associated with other congenital heart defects. Often the associated defect causes more problems than the ASD itself.

Some congenital heart defects may be passed down in certain families. Most atrial septal defects occur by chance. There is no clear reason why they happen.

Many children have no symptoms and seem healthy. If the ASD is large, your child may have symptoms. Your child may:

• Tire easily
• Have fast breathing
• Have shortness of breath
• Grow slowly
• Have respiratory infections often
• Have abnormal heart rhythm (arrhythmias)

Older children and adults with ASDs may have migraine headaches. But it's not clear if the ASD is the cause. A small blood clot that forms in the bloodstream that may cause a stroke can be linked to ASD in older children and adults. But it does not seem that closing the defect or taking blood thinners (anticoagulants) decreases risk.

The symptoms of ASD can seem like other health conditions. Have your child see their doctor for a diagnosis.

Your child's doctor may have heard a heart murmur when listening to your child's heart with a stethoscope. The heart murmur is from the abnormal flow of blood through the heart.

Your child may need to see a pediatric cardiologist for a diagnosis. This is a doctor with special training in treating heart problems in children. This doctor will examine your child and listen to your child's heart and lungs. They will find out where the murmur is best heard and how loud it is. Your child may have some tests, such as:

• Chest X-ray. This test may show an enlarged heart. Or it may show changes in your child's lungs because of the blood flow changes caused by an ASD.
• Electrocardiogram (ECG). This test records the electrical activity of the heart. It shows abnormal rhythms (arrhythmias) that may be caused by an ASD. It can also find heart muscle stress caused by an ASD.
• Echocardiogram (echo). This test uses sound waves to make a moving picture of the heart and heart valves. An echo can show the blood flow through the atrial septal opening and find out how big the opening is.
• Cardiac catheterization. This test uses a thin, flexible tube (catheter) put near the heart. Contrast dye is used to get even clearer pictures. In some children, this procedure may be used to close the ASD.

Treatment will depend on your child's symptoms, age, and general health. It will also depend on how severe the condition is. The most common type of ASD may close on its own as your child grows.

Once an ASD is diagnosed, your child's cardiologist will check your child to see if the defect is closing on its own. An ASD will often be fixed if it hasn't closed by the time a child starts school. The decision to close the ASD may also depend on the size of the defect or the symptoms caused by the defect.

Treatment may include:

• Medicine. Many children have no symptoms and don't need medicine. But medicine can help some children's hearts work better. For example, water pills (diuretics) help the kidneys get rid of extra fluid from the body.
• Surgery. Your child's ASD may be repaired by surgery. The surgery is done under general anesthesia. The defect may be closed with stitches or a special patch.
• Device closure. Some children may have their ASDs closed with this procedure. The doctor uses cardiac catheterization to put a special device (septal occluder) in the open ASD. The device stops blood from flowing through the ASD. The ASD must meet certain requirements to be able to be closed in this way.

Large ASDs may cause lung problems, such as high blood pressure in the lungs, over time if not treated. This is because the extra blood passing through the defect and then into the lungs may harm the vessels in the lungs.

All children with an ASD need to be cared for by a pediatric cardiologist. Most children who have had an ASD repair will live healthy lives. After the repair, your child's doctor may want your child to take antibiotics. This will prevent an infection of the heart lining (bacterial endocarditis).

With early diagnosis and repair of an ASD, children usually do very well. They don't need much follow-up care. Children are more likely to have problems if an ASD is diagnosed later in life and never repaired. Or they may have problems if complications occur after closing the defect.

Some children develop high blood pressure in the lungs (pulmonary hypertension). These children should have follow-up care at a center that specializes in congenital heart disease.

Talk with your child's doctor about the outlook for your child.

Contact your child's doctor if your child has new symptoms or symptoms get worse. Symptoms may include:

• Tiredness that gets worse
• Troubled breathing
• Fast breathing
• Racing or fluttering heartbeat (palpitations)
• Poor feeding

• An ASD is an opening in the wall dividing the two upper chambers of the heart.
• Symptoms include tiring easily, fast breathing, shortness of breath, poor growth, arrhythmias, and frequent respiratory infections.
• ASDs range from small to large.
• Small ASDs may close on their own. ASDs that are large or cause symptoms can be repaired.
• Most children who have had an ASD repair will live healthy lives.

Tips to help you get the most from a visit to your child's doctor:

• Know the reason for the visit and what you want to happen.
• Before your visit, write down questions you want answered.
• At the visit, write down the name of a new diagnosis, and any new medicines, treatments, or tests. Also write down any new instructions your doctor gives you for your child.
• Know why a new medicine or treatment is prescribed and how it will help your child. Also know what the side effects are.
• Ask if your child's condition can be treated in other ways.
• Know why a test or procedure is recommended and what the results could mean.
• Know what to expect if your child does not take the medicine or have the test or procedure.
• If your child has a follow-up appointment, write down the date, time, and purpose for that visit.
• Know how you can contact your child's doctor after office hours and on weekends and holidays. This is important if your child becomes ill and you have questions or need advice.