What is atrial septal defect (ASD)?

An atrial septal defect (ASD) is a hole in the wall that separates the atria (the smaller upper chambers) of the heart. The wall that separates the chambers is called the septum. The hole can make the right side of the heart work harder than usual.

What causes an ASD?

In most cases, there is no clear cause of an ASD. ASDs often happen at random. It is not anyone’s fault.

How can an ASD affect my child’s health?

The ASD allows for extra blood flow to the lungs. In most cases, there may be no symptoms. But the extra blood flow can damage the lungs and make the heart grow larger than usual.

If left untreated, lung damage can become permanent and life-threatening. Some children can also develop pneumonia (build-up of fluid in the lungs) or have asthma-like breathing problems.

Are All ASDs the Same?

There are 4 types of ASD. Some of these defects can involve other heart structures:

  • Ostium secundum ASD is the most common type. This is when the septum does not close completely while the heart is developing.
  • Ostium primum ASD is a defect in the lower part of the atrial septum. It is accompanied by a defect in one of the valves (openings that lets blood in and out).
  • Sinus venosus ASD is a hole between the atria and involves an abnormal drainage of a vein to the right atrium.
  • Coronary sinus ASD is very rare. It is when there is a hole in the coronary sinus (a part of the heart that carries blood from the heart’s main vein into the right side of the heart).

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