Atrial septal defect (ASD) is a hole in the wall between the heart’s two upper chambers. ASD is a congenital heart defect, meaning it is present from birth.

In some cases of ASD, a small hole may only require monitoring and may close by itself. With larger holes, people may need surgery to repair the hole and prevent complications.

People may receive a diagnosis of ASD as an infant or child or during adulthood. Depending on the size of the hole, it may or may not cause symptoms.

This article explains ASD, its causes, diagnosis, treatment, and outlook.

The heart has four chambers which consist of two lower chambers, called the right and left ventricles, and two upper chambers, called the right and left atria. A wall called the septum divides the left and right sides.

These four chambers work as pumps to perform the cycle of oxygenating blood and supplying it to the body.

The right side of the heart pumps deoxygenated blood to the lungs to become oxygenated, while the left side of the heart pumps oxygenated blood to the rest of the body.

It is natural to have a hole between the upper chambers at birth. This opening allows blood to travel away from the lungs of a fetus before birth.

Fetal circulation differs from postnatal circulation as the blood does not need to go to the lungs. The placenta does the job that the lungs will do after birth.

After birth, the opening is not necessary and usually closes up several weeks or months following birth. ASD occurs if the hole is larger than usual and does not close up.

A small hole may not cause problems, but a larger hole may lead to complications.

ASD can cause blood to travel from the left to the right atrium and enter the lungs’ arteries. This may increase the workload of the heart and lungs and may damage the lung arteries.

Learn about the anatomy of the heart.

There are four different types of ASD, depending on the location of the hole:

  • Ostium secundum: A hole in the center of the atrial septum, which is the wall dividing the two upper chambers.
  • Ostium primum: A hole lower down in the atrial septum.
  • Sinus venosus: A hole toward the back of the atrial septum, near one of the large veins that empty into the right atrium. The large veins are the superior vena cava and the inferior vena cava.
  • Coronary sinus: A hole in the wall between the coronary sinus, a collection of veins in the heart, and the left upper chamber.

Babies born with ASD may not display symptoms. Symptoms may occur with a larger ASD, such as:

In some cases, people may not experience any symptoms until adulthood.

It is unclear what causes ASD, but it may be due to a combination of genetic mutations and risk factors. Certain factors during pregnancy may affect development and play a part in ASD.

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Risk factors for ASD may include:

Potential complications of ASD include:

  • atrial arrhythmias, such as atrial fibrillation and atrial flutter, when the upper heart chambers beat out of time with the lower heart chambers, causing an irregular heartbeat and affecting blood flow
  • pulmonary hypertension, which is high blood pressure in the arteries of the lungs and heart
  • right-sided heart failure, in which the right side of the heart is unable to properly pump blood
  • stroke or transient ischemic attack (TIA)
  • Eisenmenger syndrome — a life threatening condition in which there is an irregular flow of blood to the heart and lungs

A doctor may diagnose ASD at birth, or people may not receive a diagnosis until adulthood.

To diagnose ASD, a doctor will listen to the heart with a stethoscope. A murmur or whooshing sound may indicate ASD. A doctor will then confirm this with other tests, such as an echocardiogram.

An echocardiogram is an ultrasound that allows a doctor to examine the structure of the heart and how well it is functioning.

A doctor will place a device called a transducer on the chest to create sound waves that bounce off the heart. A computer then turns these sound waves into a moving image of the heart.

A doctor may also use CT and MRI scans to examine the structure of the heart. Although a chest X-ray cannot help diagnose ASD, it can show abnormalities such as an enlarged heart and blood vessels.

Learn more about an echocardiogram.

If an ASD is small, people may not require treatment, and doctors may monitor the hole with echocardiography to see if it closes by itself.

For a larger ASD, people may require surgery to close the hole to prevent complications. There are two types of surgery people may have to treat ASD:

  • Transcatheter closure: During transcatheter closure, a doctor will place a small, flexible tube called a catheter into a blood vessel, such as in the arm, neck, or groin, to reach the heart. A doctor will then insert an implant or mesh to close the hole.
  • Open heart surgery: For open heart surgery, a surgeon will make a cut into the chest to reach the heart. A surgeon will then be able to insert a mesh, patch, or sew the hole close.

Follow-up hospital visits are always necessary, but their frequency depends on person’s age and whether there is any residual shunt.

Following surgery, people may need to limit their physical activity for a short time.

People who have had ASD closure or have a small, untreated ASD will be able to carry out usual activities and exercise without any extra risk.

People with complications from ASD, such as pulmonary hypertension, may need to avoid high level sports.

The National Heart, Lung, and Blood Institute (NHLBI) advises the following lifestyle choices for people with congenital heart defects:

  • attend any scheduled health checkups and take any medications as a doctor prescribes
  • attend regular dental checkups and maintain good oral hygiene
  • eat a heart-healthy diet containing plenty of vegetables, fruit, and whole grains
  • maintain regular physical activity, and check with a doctor if unsure about safe activity levels
  • avoid smoking
  • achieve and maintain a moderate weight
  • manage stress and learn techniques to relax
  • seek professional help or support if ASD is affecting mental health
  • receive any routine vaccinations
  • make a doctor aware of ASD history if taking any new medications or receiving any surgery

Learn about the best foods for heart health.

People must contact a doctor if they notice any symptoms of ASD, complications from ASD, or complications following surgery.

If people notice any signs of a stroke or heart attack, call 911 or seek emergency medical attention.

If people have untreated ASD and are planning to become pregnant, they can discuss any risks with a doctor. With a repaired ASD, the risk in pregnancy is usually very low.

An ASD smaller than 8 millimeters (mm) may close up by itself within the first year after birth. An ASD larger than 8 mm usually requires surgery to close the hole.

In adults with small defects, regular monitoring every 2–3 years can help detect any issues with the structure or functioning of the heart.

The outlook is excellent for people with ASD who receive any necessary treatment. Without treatment, ASD may lead to complications such as arrhythmias, pulmonary hypertension, right heart failure, or stroke.

ASD is a hole in the wall between the upper right and left chambers of the heart. ASD is a congenital heart defect that occurs at birth, possibly due to genetics or risk factors during pregnancy.

In some cases, small holes may only require monitoring and may close by themselves. For larger holes, people may require surgery to close the hole and prevent complications.

With treatment, the outlook for ASD is excellent. People will require routine monitoring with a cardiologist.