Atrial Septal Defect (ASD)

Atrial Septal Defect (ASD) is an acyanotic heart defect caused by the Foramen Ovale not closing after birth.

Most children with ASD are asymptomatic.

• Babies are born with a hole between their left and right atrium called the Foramen Ovale.  This generally closes 1-2 days after birth.  ASD occurs when this hole does not close.
• The left atrium has a slightly higher pressure and lower pulmonary vascular resistance than the right.  This causes the blood to be shunted from left to right.  Blood flows where there is the least resistance.
• Chronic left to right shunting results in an increased pulmonary blood flow, which can cause an overload to the heart and the lungs.  This has the possibility to cause more severe problems if the hole is not repaired.
• Shunting can also cause volume overload to the right ventricle due to the additional blood being pumped through.  This can cause a delay in the pulmonary valve closing.
• Due to shunting, pulmonary blood flow can be 2 x the systematic blood flow, as a lot of blood is travelling back to the lungs through the hole.
• Due to the hole in the heart, this causes oxygenated blood to go back to the lungs, meaning less oxygenated blood is pumped around the body.

• Hypoxemia - Can cause low saturations as there is less oxygen in the blood due to less oxygenated blood being pumped around the body.
• Pulmonary Hypertension - Due to the increased amount of blood going to the lungs, this can cause increased blood pressure.  This causes the right ventricle to work harder, which could cause the muscle to become weak.

The type of repair depends on the size and area of the septum involved.  A transoesophageal echocardiogram is carried out to find out if the hole can be closed with a catheter.

• Cardiac Catheter Device Closure - A catheter is inserted into a vein in the groin and is passed up to the heart.  The device used to close the hole is inside a sheath which is then pushed up into the catheter and passed into the heart.  X-ray and transoesophageal echocardiogram are used to ensure that the device is in the correct position.  Once the device is in place, it opens either side of the hole to close it off and the catheter is removed.
• Open Heart Surgery - The surgeon will make an incision in the chest and depending on the size of the hole it will either be covered with a patch, or will be closed with stitches.