Atrial / Ventricular Septal Defect

A defect in the septum of the heart is often called a hole in the heart. It is the most common heart problem that babies are born with. Many defects in the septum close themselves and cause no problems. Otherwise, medicines or surgery can help. Most babies born with a defect in the septum survive well into adult life.

The heart is complex but (looking at the diagram below), you can see there are basically four chambers inside it. The left and right atria are roughly on top and the bigger stronger ventricles are on the bottom.

heart with septum

The left and right sides of the heart are divided by a wall - this is called the septum. When it is between the atria, it is called the atrial septum. When it is between the ventricles it is called the ventricular septum. The septum keeps blood from the right and left sides of the heart from mixing. This is important because the blood in the left ventricle is loaded with oxygen for the rest of the body to use. The blood in the right ventricle has already given all its oxygen to the body and needs to be loaded with oxygen again by the lungs. If they mix, the blood sent out to the body will have less oxygen for the body to use.

For full explanation of the structure and function of the heart see separate leaflet called 'Heart and Blood Vessels'.

The heart starts out as a simple tube. It needs to change a lot as your baby develops within the womb. By the time you are eight weeks pregnant your baby should have four chambers in their heart. The septum develops parts made of muscle and other parts made of membrane. If the septal wall has not developed properly by this time, the baby may be born with either an atrial or ventricular septal defect. This means there is a gap in the septum. This is sometimes called a hole in the heart. There may be more than one hole. The size and position of the hole can also vary. Small holes create fewer problems for the baby and may go unnoticed.

Sometimes the septal problem occurs on its own. Other times it may occur with other heart problems or as part of an inherited condition. Most often the problem is not associated with any other medical condition.

In about 20 cases out of 100 the septal defect may be caused by a different problem such as diabetes in the mother. It is also sometimes due to when a mother has used cannabis in pregnancy or continued to drink alcohol heavily throughout the pregnancy.

Holes can also develop in the septum after a heart attack (myocardial infarction) in adults. These are slightly different. They tend to affect the muscle part of the septum. Babies tend to have gaps in the membrane part of the septum.

Septal defects are the most common heart problem that babies are born with. About four babies in every 1,000 born will have a problem with their heart or major blood vessels. Of those four babies, about two will have problems with their ventricular septum. Ventricular defects are much more common than atrial defects. Baby girls are slightly more likely to have the problem than boys.

The problems depend on the size of the hole (defect). Small holes cause few or no symptoms. However, when your baby has their checks at the doctors, the doctor may notice a murmur. This is caused by the unusual blood flow in the heart.

With slightly bigger holes, early symptoms may include sweating and becoming out of breath and tired quickly when feeding. Feeding is exercise for a baby and the extra effort needed brings out the symptoms. Not putting on weight is another warning sign and these babies also tend to have more chest infections than usual. These things usually start to happen between 4 and 6 weeks of age.

When the holes are large the things that happen are similar but more severe.

Babies who only have holes in their heart do not tend to go blue. Babies who go blue when they are stressed tend to have more complex heart or lung problems.

Your doctor may hear a murmur, or you have concerns that your baby is not putting on weight or is finding feeding difficult. Then your doctor may ask a children's specialist (paediatrician) to see your baby. They may ask for a chest X-ray or a special ultrasound scan of the baby's heart. This is called an echocardiogram and will show the structure of their heart. It will also show where the hole is and how big it is. It will check that there are no other heart problems present. These are important when deciding how to help the problem.

If the echocardiogram could not see all the problems, or the problems were very complex, it may be necessary to do cardiac catheterisation. In this test, dye that can be seen by X-rays is put into the blood vessels. X-rays are then taken as the blood passes through the heart. This allows the doctors to see exactly where the problems are in the heart.

Small holes quite commonly close on their own in the first year of life. If they haven't closed by the time the child is two years old, they are very unlikely to close on their own. Most small holes do not require any treatment.

Medicines can be used to help the symptoms that can occur if the hole is larger. These may include medicines to relieve the pressure on the heart and lungs, and also to help the heart pump effectively. Giving very high-calorie feeds less often, will reduce the effort your baby needs to feed.

Surgery can be used to block the hole. There are various different ways to close the hole. The most common way is to open the ribcage and operate directly on the heart, whilst a machine does the heart's job - a by-pass machine.

More recently techniques have been developed where a small blocking device (called an occluder) is placed into the heart. This is inserted through a blood vessel so that there is no need for open heart surgery. The occluder is then moved into place with guide wires to block the hole. This procedure may only be available in specialist hospitals.

Sometimes abnormalities of the heart rhythm can happen during or after surgery. These can usually be treated.

Small residual holes are often found after surgery. If they become problematic, it may be necessary to re-operate.

If the hole is found, most children do very well, although they will need to be seen by a heart specialist for the rest of their lives. Testing (after treatment) will allow doctors to advise on what amount of exercise is safe for the child.

As adults, further problems may develop. These are usually with the heart valves. These control the normal flow of blood around the heart. Children born with a hole in the heart should be advised how to take good care of their teeth. This is to minimise the risks of developing serious infections (endocarditis) which can damage the heart valves.

Women who have had holes in the heart may need specialist advice when they are planning to become pregnant. They will need to be seen regularly throughout their pregnancy.

British Heart Foundation

Greater London House, 180 Hampstead Road, London, NW1 7AW
Tel (Heart Help Line): 0300 330 3311 Web:

Children's Heart Federation

Level One, 2-4 Great Eastern Street, London, EC2A 3NW
Tel (free info line): 0808 808 5000 Web:

Original Author:
Dr Tim Kenny
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Peer Reviewer:
Dr Tim Kenny
Document ID:
13795 (v1)
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