Atrial Septal Defect (ASD)

An atrial septal defect (ASD) is a hole in the part of the septum that separates the atria. (The atria are the upper chambers of the heart.)

An ASD allows oxygen-rich blood to flow from the left atrium into the right atrium, instead of flowing into the left ventricle as it should. So, instead of going to the body, the oxygen-rich blood is pumped back to the lungs, where it has just been.

Cross-Section of a Normal Heart and a Heart With an Atrial Septal Defect

Atrial Septal Defect Anatomy

Figure shows the normal structure and blood flow in the interior of the heart. Figure B shows a heart with an atrial septal defect. The hole allows oxygen-rich blood from the left atrium to mix with oxygen-poor blood from the right atrium.

  • Your heart has two sides, separated by an inner wall called the septum. An atrial septal defect (ASD) is a hole in the upper part of the septum, which separates the atria.
  • Atrial septal defects allow blood to pass from the left side of the heart to the right side. This means that oxygen-rich blood can mix with oxygen-poor blood. As a result, some oxygen-rich blood is pumped to the lungs instead of out to the body.
  • Atrial septal defects can be small or large. Many small ASDs close on their own as the heart grows during childhood. Large holes in the septum are less likely to close on their own over time.
  • A heart murmur (an extra or unusual sound heard during a heartbeat) is the most common sign of both ASD. If an ASD causes heart failure, signs and symptoms may include fatigue (tiredness), tiring easily during physical activity, shortness of breath, a buildup of blood and fluid in the lungs, and a buildup of fluid in the feet, ankles, and legs.
  • Many babies who are born with atrial septal defects have no signs or symptoms.
  • Doctors usually diagnose holes in the heart based on results from a physical exam and tests and procedures. The exam findings for an ASD often aren't obvious, so the diagnosis sometimes isn't made until later in childhood or even adulthood.
  • Many holes in the heart don't need treatment, but some do. Most holes in the heart that need treatment are repaired in infancy or early childhood. Sometimes, adults are treated for holes in the heart if problems develop.
  • The treatment your child receives depends on the type, location, and size of the hole. Other factors include your child's age, size, and general health. Holes in the heart are treated with catheter procedures or surgery.
  • The outlook for children who have ASDs is excellent. Advances in treatment allow most children who have these heart defects to live normal, active, and productive lives with no decrease in lifespan.
  • Many children who have atrial septal defects need no special care or only occasional checkups with a cardiologist (heart specialist) as they go through life.

Types of Atrial Septal Defects

An atrial septal defect can be small or large. Small ASDs allow only a little blood to flow from one atrium to the other. Small ASDs don't affect the way the heart works and don't need any special treatment. Many small ASDs close on their own as the heart grows during childhood.

Medium to large ASDs allow more blood to leak from one atrium to the other, and they're less likely to close on their own. Most children who have ASDs have no symptoms, even if they have large ASDs.

The three major types of ASDs are:

  • Secundum. This defect is in the middle of the atrial septum. It's the most common form of ASD. About 8 out of every 10 babies born with ASDs have secundum defects. At least half of all secundum ASDs close on their own. However, this is less likely if the defect is large.
  • Primum. This defect is in the lower part of the atrial septum. It often occurs along with problems in the heart valves that connect the upper and lower heart chambers. Primum defects aren't very common, and they don't close on their own.
  • Sinus venosus. This defect is in the upper part of the atrial septum, near where a large vein (the superior vena cava) brings oxygen-poor blood from the upper body to the right atrium. Sinus venosus defects are rare, and they don't close on their own.

Atrial Septal Defect Complications

Over time, if an atrial septal defect isn't repaired, the extra blood flow to the right side of the heart and lungs may cause heart problems. Usually, most of these problems don't show up until adulthood, often around age 30 or later. Complications are rare in infants and children.

Possible complications include:

  • Right heart failure. An ASD causes the right side of the heart to work harder because it has to pump extra blood to the lungs. Over time, the heart may become tired from this extra work and not pump well.
  • Arrhythmias. Extra blood flowing into the right atrium through an ASD can cause the atrium to stretch and enlarge. Over time, this can lead to heart arrhythmias (irregular heartbeats). Arrhythmia symptoms may include palpitations or a rapid heartbeat.
  • Stroke. Usually, the lungs filter out small blood clots that can form on the right side of the heart. Sometimes a blood clot can pass from the right atrium to the left atrium through an ASD and be pumped out to the body. This type of clot can travel to an artery in the brain, block blood flow, and cause a stroke.
  • Pulmonary hypertension (PH). PH is increased pressure in the pulmonary arteries. These arteries carry blood from your heart to your lungs to pick up oxygen. Over time, PH can damage the arteries and small blood vessels in the lungs. They become thick and stiff, making it harder for blood to flow through them.

These problems develop over many years and don't occur in children. They also are rare in adults because most atrial septal defects either close on their own or are repaired in early childhood.

What Causes Atrial Septal Defects?

Mothers of children who are born with atrial septal defects (ASDs) or other types of heart defects often think that they did something wrong during the pregnancy to cause the problems. However, most of the time, doctors don't know why congenital heart defects develop.

Heredity may play a role in some heart defects. For example, a parent who has a congenital heart defect is slightly more likely than other people to have a child with the problem. Very rarely, more than one child in a family is born with a heart defect.

Children who have genetic disorders, such as Down syndrome, often have congenital heart defects. Half of all babies who have Down syndrome have congenital heart defects.

How Are Atrial Septal Defects Diagnosed?

Physical Exam

During a physical exam, your child's doctor will listen to your child's heart and lungs with a stethoscope. The doctor also will look for signs of a heart defect, such as a heart murmur or signs of heart failure.


Echocardiography (ECHO) is a painless test that uses sound waves to create a moving picture of the heart. ECHO allows the doctor to clearly see any problem with the way the heart is formed or the way it's working.

ECHO is an important test for both diagnosing a hole in the heart and following the problem over time. ECHO can show problems with the heart's structure and how the heart is reacting to the problems. ECHOwill help your child's cardiologist decide whether and when treatment is needed.

Electrocardiogram (ECG, EKG)

An electrocardiogram is a simple, painless test that records the heart's electrical activity. The test shows how fast the heart is beating and its rhythm (steady or irregular). It also records the strength and timing of electrical signals as they pass through each part of the heart.

An EKG can detect whether one of the heart's chambers is enlarged, which can help diagnose a heart problem.

Chest X Ray

A chest x ray is a painless test that creates pictures of the structures in the chest, such as the heart and lungs. This test can show whether the heart is enlarged or whether the lungs have extra blood flow or extra fluid, a sign of heart failure.

Pulse Oximetry

Pulse oximetry shows how much oxygen is in the blood. For this test, a small sensor is attached to a finger or toe (like an adhesive bandage). The sensor gives an estimate of how much oxygen is in the blood.

Cardiac Catheterization

During cardiac catheterization, a thin, flexible tube called a catheter is put into a vein in the arm, groin (upper thigh), or neck and threaded to the heart.

Special dye is injected through the catheter into a blood vessel or a chamber of the heart. The dye allows the doctor to see the flow of blood through the heart and blood vessels on an x-ray image.

The doctor also can use cardiac catheterization to measure the pressure inside the heart chambers and blood vessels. This can help the doctor determine whether blood is mixing between the two sides of the heart.

Cardiac catheterization also is used to repair some heart defects.

How Are Atrial Septal Defects Treated?

Periodic checkups are done to see whether an atrial septal defect closes on its own. About half of all ASDs close on their own over time, and about 20 percent close within the first year of life.

When treatment of an ASD is required, it involves catheter or surgical procedures to close the hole. Doctors often decide to close an ASD in children who still have medium to large holes by the time they're 2 to 5 years old.

Catheter Procedure to Treat Atrial Septal Defects

Until the early 1990s, surgery was the usual method for closing all atrial septal defects. Now, thanks to medical advances, doctors can use catheter procedures to close secundum ASDs, the most common type of ASD. For this procedure, your child is given medicine so he or she will sleep through it and not feel any pain.

During the procedure, the doctor inserts a catheter (a thin, flexible tube) into a vein in the groin (upper thigh) and threads it to the heart's septum. The catheter has a tiny umbrella-like device folded up inside it.

When the catheter reaches the septum, the device is pushed out of the catheter and positioned so that it plugs the hole between the atria. The device is secured in place and the catheter is withdrawn from the body.

Within 6 months, normal tissue grows in and over the device. There is no need to replace the closure device as the child grows.

Doctors often use echocardiography (echo) or transesophageal echo (TEE) as well as angiography to guide them in threading the catheter to the heart and closing the defect.

Catheter procedures are much easier on patients than surgery because they involve only a needle puncture in the skin where the catheter is inserted. This means that recovery is faster and easier.

The outlook for children having this procedure is excellent. Closures are successful in more than 9 out of 10 patients, with no significant leakage. Rarely, a defect is too large for catheter closure and surgery is needed.

Surgery for Atrial Septal Defects

Open-heart surgery generally is done to repair primum or sinus venosus ASDs. Your child is given medicine so that he or she will sleep through the surgery and not feel any pain.

During the surgery, the cardiac surgeon makes an incision (cut) in the chest to reach the ASD. He or she then repairs the defect with a special patch that covers the hole. Your child is placed on a heart-lung bypass machine so that the heart can be opened to do the surgery.

The outlook for children after ASD surgery is excellent. On average, children spend 3 to 4 days in the hospital before going home. Complications, such as bleeding and infection, from ASD surgery are very rare.

Some children may develop inflammation of the outer lining of the heart, a condition called pericarditis. This causes fluid to collect around the heart in the weeks after surgery. This complication of heart surgery usually resolves with medicine.

While in the hospital, your child will be given medicines as needed to reduce pain or anxiety. The doctors and nurses at the hospital will teach you how to care for your child at home.

They will talk about preventing blows to the chest as the incision heals, limiting activity while your child recovers, bathing, scheduling followup medical appointments, and determining when your child can go back to his or her regular activities.

Living With Atrial Septal Defects

Small ASDs often close on their own and don't cause complications or require treatment. Children and adults who have small ASDs that don't close and don't cause symptoms are healthy and don't need treatment.

Many others who have ASDs that don't close have catheter procedures or surgery to close the holes and prevent possible long-term complications. Children recover well from these procedures and lead normal, healthy lives. Adults also do well after closure procedures.

Ongoing Care

Arrhythmias. The risk of arrhythmias (irregular heartbeats) increases before and after surgery. Adults who have ASDs and are older than 40 are especially likely to have arrhythmias. People who had arrhythmias before surgery are more likely to have them after surgery.

Followup care. Regular followup care into adult life is advised for people who have had:

  • An ASD repaired as an adult
  • Arrhythmias before and after surgery
  • An ASD repaired with a catheter procedure
  • Pulmonary hypertension (increased pressure in the pulmonary arteries) at the time of surgery


Children who have severe heart defects may be at slightly increased risk for infective endocarditis (IE). IE is a serious infection of the inner lining of your heart chambers and valves.

ASDs aren't associated with a risk of IE, except in the 6 months after repair (for both catheter procedures and surgery).

In a few situations, your child's doctor or dentist may give your child antibiotics before medical or dental procedures (such as surgery or dental cleanings) that could allow bacteria into the bloodstream. Your child's doctor will tell you whether your child needs to take antibiotics before such procedures.

To reduce the risk of IE, gently brush your young child's teeth every day as soon as they begin to come in. As your child gets older, make sure he or she brushes every day and sees a dentist regularly. Talk with your child's doctor and dentist about how to keep your child's mouth and teeth healthy.

Special Considerations for Children and Teens with Atrial Septal Defects

  • Activity. Children who have a repaired or closed ASD have no restrictions on their activity.
  • Growth and development. Children who have ASDs don't have growth or development problems.
  • Regular health care. Your child should see his or her regular doctor for routine health care.
  • Additional surgery or procedures. When a child has an ASD, but no other heart defects, additional surgery isn't needed.

Special Considerations for Adults with Atrial Septal Defects

When an adult has an ASD repaired, his or her cardiologist or surgeon will explain what to expect during the recovery period and when to return to driving, working, exercising, and other activities.

Reference: The National Heart, Blood, and Lung Institute

Last updated April 27, 2017

This information is for general educational uses only. It may not apply to you and your personal medical needs. This information should not be used in place of a visit, call, consultation with or the advice of your physician or health care professional.

Communicate promptly with your physician or other health care professional with any health-related questions or concerns.

Be sure to follow specific instructions given to you by your physician or health care professional.

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