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Atrial Septal Defect (ASD)

The atrial septum is the wall of tissue and muscle between the upper two chambers (atria) of the heart. An ASD is a hole in this wall. A hole or defect such as this allows both upper chambers of the heart (atria) to communicate and permits an abnormal flow of blood from one chamber to the other. This means that the oxygen-rich and the oxygen-poor blood, instead of being kept separate, are allowed to mix and flow from the heart to the body and lungs.

This type of heart problem can occur on its own, but may also occur together with other forms of congenital heart disease.


What are the signs and symptoms of atrial septal defect?

Children with an atrial septal defect (or PFO) may only show mild symptoms of having a heart condition, or may not have any symptoms at all.

Frequent chest infections can be a sign that the oxygenation process is not working efficiently due to extra blood flow to the lungs.

Large defects can cause extra strain on the heart causing the right-hand side of the heart to dilate (stretch). Babies with large defects may be breathless and struggle to feed and gain weight. Older children may show a reduced tolerance for exercise.

The extra flow of blood to the lungs usually produces heart murmurs in children (an abnormal heart sound) that can be detected on routine health checks. This is a common reason for referral.


How is atrial septal defect diagnosed?

Your child will have an echocardiogram, a non-invasive, high frequency ultrasound scan of the heart. It allows doctors to the see the structure of the atrial valve and assess any abnormal blood flow through the heart, as well as the overall performance of the heart and circulatory system.

They may also have an electrocardiogram (ECG). This measures electrical activity in the heart to see how well it is working. Doctors will look to see whether the right side of the heart has thickened and whether it is working harder than it should be.


How is atrial septal defect treated?

The treatment your child needs will depend on the severity of the defect.

Small, central atrial defects can close spontaneously after a few years, and your child may only require regular supervision in an outpatient clinic.

If the defect is slightly larger, and surrounded by good margins of heart tissue, a key hole procedure known as cardiac catheterisation can be used to close the hole. This is usually undertaken as a day-case procedure.

Large central defects or other types of ASD may require open-heart surgery for repair. The type of operation depends upon the position of the defect and any associated tissue damage (lesions).


Further reading

Download the BHF atrioventricular septal defect factsheet (PDF)

Read about atrial septal defect on the Children's Heart Federation website