An atrioventricular septal defect (AVSD) is a condition in which there is a hole between the chambers of the left and right sides of the heart. Additionally, the valves between the chambers may not have formed properly.

An AVSD is a congenital condition, meaning a person is born with it. They will require surgery to repair the hole or holes. The age at which a person has surgery will depend on the severity of their AVSD and how healthy they are.

There is no cure for an AVSD, and it usually requires lifelong management. Doctors may also refer to an AVSD as an endocardial cushion defect or an atrioventricular canal defect.

This article explores the symptoms, causes, diagnosis, and treatment of an AVSD. It also explains the outlook for people with this condition.

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According to estimates from the Centers for Disease Control and Prevention (CDC), approximately 1 in 1,859 infants are born with an AVSD in the United States every year.

When a person has an AVSD, there is a hole between the chambers of the left and right sides of their heart.

The heart has four chambers. The top two chambers are the atria, and the bottom two are the ventricles. In a person with an AVSD, a hole may connect two or more chambers. The more chambers this hole connects, the more severe the AVSD is.

There are two types: a complete AVSD and a partial — or incomplete — AVSD.

Complete AVSD

This is the most severe type of AVSD.

The hole occurs in the center of the heart, where the septa — the walls separating the top two chambers from the bottom two — usually meet.

There is also one common valve in the middle of the heart instead of two separate valves. In contrast, a typical heart has a valve on either side — the tricuspid valve on the right and the mitral valve on the left.

This means that the hole in the heart of a person with a complete AVSD connects all four chambers.

Partial AVSD

With a partial AVSD, the hole may sit slightly off-center and only affect two of the heart’s chambers.

For example, if the hole is closer to the top of the heart, it only affects the atria, causing an atrial septal defect. Alternatively, if the hole is near the bottom of the heart, doctors call this a ventricular septal defect.

Unlike a complete AVSD, a person with a partial AVSD usually has a tricuspid valve and a mitral valve. However, the mitral valve may not close completely, meaning blood flows backward. When this happens, the heart has to work harder to push blood in the right direction.

Signs and symptoms of a complete AVSD are usually noticeable soon after an infant is born, and include:

If an infant has a partial AVSD, these symptoms may not present as quickly. Several years may pass before they receive a diagnosis.

Signs of worsening AVSD may include:

The causes of AVSDs are unknown.

However, the CDC notes that certain genetic changes may increase the risk of developing an AVSD. For example, it states that AVSDs are common in babies with Down syndrome.

A 2021 study found that babies with Down syndrome also tended to experience severe complications of AVSDs, such as pulmonary hypertension. The researchers note that early diagnosis and treatment were important factors for a better outlook.

In addition to genetic changes, environmental factors that a parent experiences exposure to during pregnancy can also increase the risk of congenital heart defects, such as AVSDs.

Factors that contribute to the likelihood of a congenital heart defect may include:

Some pharmacological treatments may also increase the risk of a heart defect.

If a person is concerned about taking medications during pregnancy, they should speak with a doctor. If they are following a treatment plan, it is important that they do not stop without talking with a healthcare professional first.

Healthcare professionals may diagnose an AVSD during pregnancy or after birth.

During pregnancy

Several tests can check for developmental conditions before birth. An ultrasound scan may be able to detect an AVSD, depending on the type and the size of the hole in the heart.

If a doctor suspects AVSD, they will likely request a fetal echocardiogram to confirm the diagnosis.

After birth

A doctor may hear a murmur when using a stethoscope to listen to an infant’s heart.

To eliminate other conditions, they will likely also request:

An AVSD will often require surgery.

During the procedure, surgeons close the holes in the heart with patches. If the mitral valve is beyond repair, they will replace it.

In cases of a complete AVSD, surgeons separate the common valve so that both the left and right sides of the heart have individual valves.

However, surgery is not a cure for an AVSD. People will likely need lifelong monitoring and additional treatment, especially since a leaky mitral valve is a common complication.

If surgery is too big of a risk for an infant, doctors will give them medication to prevent further complications from developing. They may also increase the baby’s caloric intake using a feeding tube to physically prepare them for surgery.

Learn more about leaky heart valves.

The outlook among infants who receive surgery is often good. However, if they do not, AVSD can be fatal.

A 2018 study cites research that suggests around 86—89% of children who receive surgery for an AVSD can live for 15 years. About 10% of these children need a second surgery within this time.

Some people with an incomplete AVSD do not experience any symptoms, although this is exceptionally rare. For example, a 2021 case study describes a 34-year-old receiving a diagnosis of an incomplete AVSD during a health exam before an operation.

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An AVSD is a hole between the chambers of the left and right sides of the heart. It occurs due to atypical fetal development and is present from birth. In people with AVSD, the valves between the chambers may also not have formed properly.

The severity of an AVSD depends on the size of the hole and how many chambers it affects. A hole in the center of the heart that connects all four chambers is the most severe form.

Doctors treat an AVSD with surgery. However, they often have to wait for an infant to grow and develop enough strength for surgery before operating.