Heart and Blood Conditions

Atrioventricular Septal Defect

What is atrioventricular septal defect?

Atrioventricular (pronounced A-tree-oh-ven-TRIK-yu-lar) septal defect (AV septal defect) is a condition in which the center of the heart is not fully formed at birth. It is also known as atrioventricular canal defect or endocardial cushion defect.

The normal heart has a total of four chambers. There are two upper chambers, called the right atrium and left atrium. There are also two lower chambers, called the right ventricle and left ventricle. There are also two heart valves that divide the atria from the ventricles (atrioventricular valves). The valve on the right side is the tricuspid valve. The valve on the left side is the mitral valve.

In AV septal defect, there is a hole in the wall (septum) between the right and left atria (atrial septal defect, ASD). There is also a hole in the septum between the right and left ventricles (ventricular septal defect, VSD).

In addition, the two atrioventricular valves are not formed correctly. A baby with AV septal defect may have just one larger valve opening in the middle, instead of one on each side of the heart.

Together, these problems may create a hole in the center of the baby's heart. As a result, blood does not flow the way it should between the chambers. So the heart has to work harder to pump blood to the lungs and the rest of the body.

Atrioventricular Septal Defect at Seattle Children’s

Our heart team has treated many children with AV septal defect. We have extensive experience with the treatment these patients may require, including surgery to close the holes in the septa, to repair the valves and to replace the valves (which some children need later in life). We also have a pediatric cardiac anesthesia team and a cardiac intensive care unit ready to care for children who undergo heart surgery.

When you come to Seattle Children’s, a team of people will take care of your child. Along with your child’s heart doctor (cardiologist), you are connected with newborn specialists (neonatologists), cardiac intensivists, lung doctors (pulmonologists), nurses, child life specialists, social workers and others, if their expertise is needed. We work together to meet all of your child’s health needs and help your family through this experience.

Seattle Children’s has been treating children since 1907. Our team members are trained in their fields and in meeting the unique needs of children. For example, the doctors who give your child anesthesia (sedation) are board certified in pediatric anesthesiology. This means they have extra years of training in how to take care of kids. Our child life specialists know how to help children understand their illnesses and treatments in ways that make sense for their age.

The Adult Congenital Heart Disease Program shared by Children’s and the University of Washington can help with care throughout your child’s life.

Atrioventricular Septal Defect in Children

It is normal for babies to have holes between the atria and the ventricles while the heart is developing in the womb. The holes should close by the time the heart is fully developed, which occurs around the seventh week of pregnancy.

In some babies, the holes in the septum do not close all the way and the atrioventricular valves do not fully form.

About 2 in every 10,000 babies are born with AV septal defect. Most of the time, it is not clear why this happened. In some cases, it may be related to a genetic condition such as Down syndrome, where up to 50% of people may have congenital heart disease.

Contact Us

Contact the Heart Center at 206-987-2015 for a cardiac referral, a second opinion or more information.