Atrial septal defect (ASD) is a congenital birth defect. It is an abnormality in the atria (the upper chambers of the heart). In ASD, the wall between the left and right chambers is not completely closed.

In a developing fetus, there is an opening between the left and right atrium. This opening allows the blood to bypass the lungs. When the baby is born, that opening is normally closed, and blood will flow to the lungs.

In babies born with ASD, blood passes from the left atrium to the right atrium. This eventually can cause problems in the lungs.

ASD occurs in about four out of every 100,000 babies. Those with minor-to-moderate defects may not suffer any complications or symptoms. Very small ASDs close on their own about 90% of the time. Those with more severe defects may have disabilities later in life.

Heart Chambers and Valves

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ASD is a congenital defect. This means that it occurs during fetal development and is present at birth. Some cases may be caused by a genetic defect or abnormality inherited from a parent. Others can be caused by illnesses suffered by the mother during pregnancy.

Most of the time, the cause is unknown.

Risk Factors

Because the cause is largely unknown, there are no known risk factors for this condition.


Symptoms include:

  • Fatigue and tiring easily during activity
  • Sweating
  • Rapid breathing, difficulty breathing, or shortness of breath
  • Persistent respiratory infections
  • Poor growth
  • Heart palpitations
  • Poor appetite
  • Heart murmur

People with minor-to-moderate defects may show no symptoms. Or, they may not begin to show symptoms until later in life.


Your doctor will ask about your symptoms and medical history. You will also be examined. Tests may include the following:

  • Chest x-ray —a test that uses radiation to take a picture of structures inside the body, especially bones
  • Echocardiogram —a test that uses high-frequency sound waves (ultrasound) to examine the size, shape, and motion of the heart
  • Doppler image of the heart
  • Cardiac catheterization —a tube-like instrument inserted into the heart through a vein or artery (usually in the arm or leg) to detect problems with the heart and its blood supply
  • Coronary angiography (patients over age 35 only)—x-rays taken after a dye is injected into the arteries, allows the doctor to look for abnormalities in the arteries
  • MRI of the chest —a test that uses magnetic waves to make pictures of structures inside the chest
  • Electrocardiogram (ECG, EKG) —a test that records the heart’s activity by measuring electrical currents through the heart muscle


Small defects that produce few or no symptoms may not require treatment. Also, many defects may close on their own without treatment. Talk with your doctor about the best treatment plan for you. Treatment options include:


For patients with large defects and who experience significant symptoms, surgery may be needed.

A new procedure may also be performed, which closes the opening without surgery. A closure device is inserted through a heart catheter, which is inserted in the groin.


After open heart surgery, antibiotics are prescribed prior to dental work or other procedures. This is to reduce the risk of developing bacterial endocarditis .

Bacterial Endocarditis

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Since the condition is a congenital defect with unknown causes, there are preventive measures. Early diagnosis and early treatment can help prevent complications