An atrioventricular septal defect (AVSD) is a congenital (present at birth) heart condition. People with this condition have an abnormal hole in the wall (or septum) that separates the two upper chambers (atria) of the heart. This is called a primum atrial septal defect. They also have an abnormal hole in the septum that separates the two lower chambers (ventricles) of the heart. This is known as a ventricular septal defect. Atrioventricular septal defects also affect the atrioventricular valves which control blood flow from the atria to the ventricles. In people with an atrioventricular septal defect, these valves are not formed properly, which can lead to an abnormal leakage of blood.

In people with atrioventricular septal defects, blood does not move through the heart correctly. More blood than normal flows to the lungs, causing the heart and lungs to work harder than normal, which can lead to congestive heart failure.

In the United States, about 2,100 babies are born with atrioventricular septal defects each year. The diagnosis accounts for about 3% of all congenital heart conditions. The condition is slightly more common among females than males. It’s also more common among babies with Trisomy 21.

The good news is that atrioventricular septal defects can be surgically corrected. Many patients who receive treatment live well into adulthood.

An atrioventricular septal defect is a birth defect that occurs when a patient’s heart does not develop in the uterus. Patients with the condition have holes in the heart where there should be walls separating different heart chambers. They also have abnormal heart valves that leak.

There are three main types of atrioventricular septal defect:

• Complete. The patient has a large hole in the wall that separates the heart’s two upper chambers (atria), as well as the wall that separates the heart’s two lower chambers (ventricles). The heart also has one valve between its upper and lower chambers, when two are usually present.
• Transitional. The patient has a hole in the wall that separates the atria and a small hole in the wall separating the ventricles.
• Partial (or incomplete). The patient has a hole in the wall that separates either the atria or the ventricles, but not both. (The upper chambers are usually affected.) Additionally, the valves between the atria and the ventricles are fused rather than being two separate valves. If the hole in the heart wall is small, this condition may not be diagnosed at birth, and a patient may live for years without realizing that they have it.

In a healthy person, the heart has four chambers and four valves. Oxygen-poor blood from the body enters the right atrium of the heart (upper right chamber) and passes through the tricuspid valve to the right ventricle (lower right chamber). From there, it passes through the pulmonary valve to the pulmonary artery so the blood can travel to the lungs to become oxygenated. The oxygen-rich blood then enters the heart’s left atrium, passing through the mitral valve to the left ventricle. Finally, it passes through the aortic valve to the aorta, a large artery that delivers oxygen-rich blood to the rest of the body.

When a baby is born with an atrioventricular septal defect, blood doesn’t flow through the heart properly. In people with the condition, extra blood can flow to the lungs resulting in pulmonary over-circulation (excessive blood flow to the lungs) and symptoms of congestive heart failure. There is an imbalance between blood flow to the lungs and blood flow to the rest of the body, which often results in heart enlargement. The increase in blood flow to the lungs stresses them and can cause babies with an atrioventricular septal defect to breath faster than normal or have difficulty feeding.

Doctors aren’t sure why some babies are born with an atrioventricular septal defect. In some cases, genetic or chromosomal abnormalities can cause the condition. An atrioventricular septal defect is common among babies who are born with Trisomy 21, as well as other syndromes. It may also run in some families.

Babies with a complete atrioventricular septal defect typically do not have symptoms until around a month or two after birth. Symptoms of a complete atrioventricular septal defect may include:

• Rapid breathing
• Shortness of breath while eating
• Poor weight gain
• Sweating
• Poor growth
• Rapid heart rate

Some babies with a partial atrioventricular septal defect may not exhibit symptoms as infants, although they may develop symptoms during adolescence or as young adults, including:

• Difficulty breathing while exercising
• Fatigue
• Heart palpitations

People with transitional atrioventricular septal defects may not experience any symptoms in childhood. They may develop symptoms of heart failure if the hole in the wall separating the ventricles is large enough. Heart failure symptoms include shortness of breath, fatigue, and the buildup of fluid in the legs, among others.

When a complete or partial atrioventricular septal defect worsens, a person with the condition may develop:

• Abnormal heart rhythms (arrhythmias)
• Congestive heart failure
• Pulmonary hypertension

These factors may increase the risk of a baby being born with atrioventricular septal defect:

• Trisomy 21 (a type of Down syndrome)
• CHARGE syndrome
• VATER association
• Ellis-van-Creveld syndrome
• Smith-Lemli-Opitz syndrome
• Holt-Oram syndrome
• 3p deletion syndrome
• Noonan syndrome
• Gestational diabetes in the mother during pregnancy
• Maternal obesity during pregnancy
• A family history of atrioventricular septal defect

Often, an atrioventricular septal defect is diagnosed during pregnancy. The condition may be discovered during an ultrasound exam during pregnancy, if it is significant enough to be detected. (An ultrasound uses sound waves to create images of a fetus within the mother’s uterus.) When doctors believe that they see an atrioventricular septal defect on a pregnancy ultrasound, they can confirm it with a fetal echocardiogram, a more detailed ultrasound exam that uses sound waves to create images of a fetus’s heart. It can identify structural abnormalities within the heart, as well as abnormalities relating to blood flow through the heart.

In other cases, atrioventricular septal defects are diagnosed after birth. When a baby is born with a complete atrioventricular septal defect, it is typically diagnosed within the first few weeks of life. Other atrioventricular septal defects may not be diagnosed for years.

Doctors can diagnose an atrioventricular septal defect by learning about a patient’s medical history, performing a physical exam, and offering diagnostic tests.

Doctors will want to learn about the patient’s medical history, including whether they have been diagnosed with a genetic or chromosomal abnormality, including Down syndrome. All babies diagnosed with Down syndrome should be assessed for atrioventricular septal defect.

During a physical exam, the doctor should look for signs of heart failure, including rapid breathing and a rapid heart rate. (They may also look for signs of Trisomy 21 if there was not a previous diagnosis.) The doctor should listen with a stethoscope for a heart murmur or other sounds that could indicate abnormalities in blood flow through the heart or heart rhythm.

Different diagnostic tests may be used to confirm the presence of an atrioventricular septal defect, including:

• Echocardiogram. This ultrasound test shows images of the heart and can identify abnormalities in its structure and blood passage through the heart. During the test, a sonographer (the medical professional who conducts ultrasound exams) places a transducer (a wand) over the patient’s chest and torso, and sound waves that the transducer receives create images of the heart. This test can show the presence of holes in the walls between heart chambers or the presence of one valve in the middle of the heart where two valves (tricuspid and mitral valves) should be.
• Electrocardiogram (ECG or EKG). This test records the heart’s electrical activity and can detect abnormalities related to heart functioning. Doctors adhere sensors, which are connected to an electrocardiogram machine, to the patient’s chest and torso. When a patient has an atrioventricular septal defect, an electrocardiogram may identify patterns of heart rhythm abnormalities and, sometimes, an enlargement of one of the heart’s chambers.
• Chest X-ray. An image of the chest cavity may show that a patient has an enlarged heart and abnormalities in the blood flow to the lungs, which are possible signs of an atrioventricular septal defect.

In some cases, doctors may use magnetic resonance imaging (MRI) or cardiac catheterization before surgery to get more precise information about the patient’s heart. (Cardiac catheterization is a procedure in which doctors insert a thin tube with a camera on its end into an artery in the groin, then thread it through blood vessels until it reaches the heart, where it can provide images from within.)

Surgery is used to correct a complete atrioventricular septal defect, but a baby who is diagnosed during the first weeks of life isn’t ready for surgery until they are 3 to 6 months old, when they are larger and heavier. However, doctors want to surgically repair the condition as soon as possible, because an atrioventricular septal defect may cause permanent lung damage if treatment is delayed for too long.

Doctors use medication to manage the condition until a baby is eligible for surgery. They may prescribe the following:

• Beta-blockers or ACE inhibitors, which may help to reduce the volume of blood that travels between the left and right chambers of the heart.
• Digoxin, a drug that helps the heart to contract or squeeze more forcefully, thereby improving circulation.
• Diuretics, which remove excess fluid from the body, making it less taxing for the heart to pump blood.

During open-heart surgery, doctors close the holes in the baby’s heart with patches to prevent blood from moving between the left and right chambers. The patches may be made of synthetic material or from the baby’s own heart lining. Doctors also repair the baby’s valves during the surgery. The single valve is separated into two valves that function independently without leaking blood.

If doctors diagnose an asymptomatic (symptom-free) baby with a partial or transitional atrioventricular septal defect, they may recommend surgery during the toddler years (ages 1 to 3 years) to patch holes and repair valve leakages. If a partial or transitional atrioventricular septal defect is not discovered until adulthood, doctors may recommend patching holes and repairing valves after diagnosis.

About 97% of patients with atrioventricular septal defects who undergo corrective surgery survive the procedure. Roughly 90% of patients who undergo surgery survive 15 years or longer. About 10% of patients who have had surgery for an atrioventricular septal defect may need additional surgery years later. Many patients live into adulthood.

Cardiologists typically monitor patients with atrioventricular septal defects for their entire lives in case complications arise. Some patients may need to restrict their physical activity.

This article was medically reviewed by Jeremy Steele, MD, a Yale Medicine pediatric cardiologist.