Complete and Partial Atrioventricular Septal Defects

What is a congenital heart condition? 

Congenital heart defects (CHD) are conditions that are present at birth and they affect the structure of the heart and how it works. They can affect how the blood flows through the heart and to the rest of the body. 

CHDs can range in severity from small holes in the heart to large missing or poorly formed areas of the heart. It is estimated that 1 in 4 babies born with a heart defect will have a critical CHD and need surgery. 

About complete atrioventricular septal defects

A complete atrioventricular septal defect (AVSD) consists of a complicated hole between the right and left side of the heart. The hole is in the centre of the heart, essentially creating two holes; one between the atria and the other between the ventricles. 

A complete atrioventricular septal defect arises during pregnancy when the common valve fails to separate into two distinct valves, and the walls that split the upper and lower chambers of the heart do not grow all the way to meet in the centre of the heart. 

About partial atrioventricular septal defects

A partial atrioventricular septal defect is very similar to a complete one, except there are no holes between the ventricles and there is usually a hole in the atrial wall near the centre of the heart. 

A partial atrioventricular septal defect usually has both valves, but one of the valves may not close fully, allowing the blood to leak backwards from the ventricle into the left atrium. 

Risks of complete atrioventricular septal defects

There are possible risks and complications that can come with complete atrioventricular septal defects, including:

• Enlargement of the heart – Increased blood flow through the heart causes it to work harder than normal, causing it to become larger.
  

• High blood pressure in the lungs – Also known as pulmonary hypertension, the hole in the heart allows oxygen rich blood to mix with oxygen poor blood. This causes the lungs to get too much blood and pressure builds.
  

• Respiratory tract infections – A hole in the heart can lead to repeat lung infections.
  
• Heart failure – If the atrioventricular septal defect is not treated correctly, the heart cannot pump enough blood to meet the needs of the body. 

An atrioventricular septal defect is also common in babies with Down syndrome, also known as trisomy 21. This is because a change in genes or chromosomes can cause heart defects. 

Risks of partial atrioventricular septal defects

While babies born with partial atrioventricular septal defects may not experience the same risks as those with complete ones, there are some risks and complications that may occur, such as arrhythmia – this is an abnormal heart rhythm. Arrhythmia causes the heart to beat too fast, too slow or erratically. When the heart doesn’t beat properly, it can’t pump blood effectively.