Atrioventricular Septal Defect (AVSD)

What is Atrioventricular Septal Defect?

(© Competence Network for Congenital Heart Defects)

Atrioventricular means ‘of the atria and the ventricles’ – the four chambers of the heart.
Septal means ‘of the septum’ – the wall between the left and right sides of the heart.
Defect means hole. So Atrioventricular Septal Defect (AVSD) means there is a hole between the atria, atrial component, which continues down between the ventricles, ventricular component.  

Instead of a two separate valves (the mitral and tricuspid valve), there is just a single common valve. This means that there is a large hole in the middle of the heart.

Because pressure is higher on the left side of the heart, blood flows from the left atrium into the right, and from the left ventricle into the right. This means that too much blood is moving at high pressure into the pulmonary artery and the lungs, and the heart is doing extra work. Often the common valve leaks either into the left or right sided atrium or both. And this also increases the work the heart has to do.

AVSD can be ‘partial’ and ‘intermediate’ as well as the complete AVSD shown above. In intermediate AVSD there is a small ventricular component. In partial AVSD there is only an atrial component and the common valve is divided into two separate valves. The left sided ‘mitral’ valve is often leaky.


AVSD can be diagnosed during pregnancy: the cross at the centre of the heart, formed by the valves and septum, which can be seen on an ultrasound scan of the baby’s heart, is missing.

If your child has Down’s Syndrome, his or her heart may have been examined to check for AVSD which occurs in nearly a quarter of children with this syndrome.

After birth your baby may be blue and may gradually become breathless, have problems feeding, and be slow to put on weight. They may have frequent chest infections.

If your baby has the partial or intermediate form of AVSD there may not be any symptoms early in life, other than a heart murmur.

The sound of extra blood being pushed towards the lungs and leaking through the valve can be heard as a heart murmur.

When a heart murmur is heard the tests used can be:

  • An ultrasound scan (echocardiogram) to see the hole and how the blood moves through the heart
  • An oxygen saturation monitor to see how much oxygen is getting into the blood
  • A chest x-ray to see the size and position of the heart
  • An ECG (electrocardiogram) to check the electrical activity
  • Checks for chemical balance in blood and urine
  • Pulse, blood pressure, temperature, and number of breaths a baby takes a minute
  • Listening with a stethoscope for changes in the heart sounds.

If your child’s heart condition is very complex AVSD may be just one of a number of defects.


Early treatment with medicine may be necessary if your child’s heart is not coping and they are in ‘heart failure’. This can mean that the lungs have become heavy or ‘wet’ with fluid and you may notice your child is working harder to breathe. A careful check will be kept on their breathing and weight as an increase can be due to fluid retention. He or she may need medicines to get rid of the extra fluid – diuretics.

If your baby has a complete AVSD, the blood pressure in the lungs will be high (pulmonary hypertension), and an operation will be needed before irreparable damage is caused to the lungs.

This is open heart surgery – the heart will need to be stopped and opened to repair it. This means that a machine will have to take over the job that the heart normally does – the heart bypass machine.  

The aim of the operation is to make the circulation of blood through the heart and lungs normal, so a patch is put over the holes between the atria and ventricles, and the valve is divided, so that there are two effective valves.

If your child has other heart defects, the kind of surgery needed will depend on how the heart can best be modified to cope with all the problems he or she has.

For most children this surgery is low risk, but it can depend on how well your child is otherwise. The doctors will discuss risks with you in detail before asking you to consent to the operation.

The length of time in hospital will usually be only 10 to 12 days, of which one or two will be spent in the intensive care and high dependency unit. Of course this depends on how well your child is before and after the surgery, and whether any complications arise.

After surgery

If the surgery is straightforward, and your child does not have other health problems, they should be completely well shortly after surgery. There will be a scar down the middle of the chest, and there may be small scars where drain tubes were used.  These fade very rapidly in most children, but they will not go altogether. Smaller scars on the hands and neck usually fade away to nothing.

Some of the following problems can occur after surgery or later in life:

  • It is common for the valves to leak a little, but if this becomes severe, they may need further repair or even replacement with an artificial valve. If the valve is replaced, this will need to be monitored to make sure the replacement is working effectively, and an artificial valve may need to be replaced as the child grows. Children with artificial valves will need to take anticoagulants for the rest of their lives, which can have a number of implications for their health and lifestyle.
  • The electrical system of the heart is sometimes damaged after surgery, causing a very fast heart beat (called tachycardia), which may need medication to keep it stable.
  • Some people go on to develop sub-aortic stenosis, a blockage below the aortic valve, which may need open heart surgery.

These problems may not become serious until the teen years or adulthood.

Author(s): Children’s Heart Federation
Last updated: 2008-12-18