Atrial Septal Defect In Children

What is an atrial septal defect?

Anatomy of the heart, normal

An atrial septal defect is an opening in the atrial septum, or dividing wall between the two upper chambers of the heart known as the right and left atria. ASD is a congenital (present at birth) heart defect. As the fetus is growing, something occurs to affect heart development during the first eight weeks of pregnancy, resulting in an ASD.

Normally, oxygen-poor (blue) blood returns to the right atrium from the body, travels to the right ventricle, then is pumped into the lungs where it receives oxygen. Oxygen-rich (red) blood returns to the left atrium from the lungs, passes into the left ventricle, and then is pumped out to the body through the aorta.

An atrial septal defect allows oxygen-rich (red) blood to pass from the left atrium, through the opening in the septum, and then mix with oxygen-poor (blue) blood in the right atrium.

Illustration of the anatomy of a heart with an atrial septal defect

Atrial septal defects occur in 6 to 8 percent of all children born with congenital heart disease. For unknown reasons, girls have atrial septal defects twice as often as boys.

What causes an atrial septal defect?

The heart is forming during the first eight weeks of fetal development. It begins as a hollow tube, then partitions within the tube develop that eventually become the septa (or walls) dividing the right side of the heart from the left. Atrial septal defects occur when the partitioning process does not occur completely, leaving an opening in the atrial septum.

Some congenital heart defects may have a genetic link, either occurring due to a defect in a gene, a chromosome abnormality, or environmental exposure, causing heart problems to occur more often in certain families. Most atrial septal defects occur sporadically (by chance), with no clear reason for their development.

What are the types of atrial septal defects?

There are four major types of atrial septal defects:

Ostium secundum atrial septal defect. This is the most common atrial septal defect, affecting 70 percent of people with atrial septal defects. It is caused when a part of the atrial septum fails to close completely while the heart is developing. This causes an opening to develop in the center of the wall separating the two atria.

Ostium primum atrial septal defect. This defect is part of atrioventricular canal defects, and is associated with a split (cleft) in one of the leaflets of the mitral valve.

Sinus venosus atrial septal defect. This defect occurs at the superior vena cava and right atrium junction. This defect is located in the area where the pulmonary veins enter the heart. As a result, the drainage of one or more of the pulmonary veins may be abnormal in that the pulmonary veins enter the right atrium rather than the left atrium.

Coronary sinus atrial septal defect. This defect is located within the coronary sinus, which is the structure in the right atrium where all the heart's own veins drain into the right atrium. It is the rarest of all atrial septal defects.

Why is an atrial septal defect a concern?

This heart defect can over time cause lung problems if not repaired. When blood passes through the ASD from the left atrium to the right atrium, a larger volume of blood than normal must be handled by the right side of the heart. This extra blood passes through the pulmonary artery into the lungs, causing higher amounts of blood flow than normal in the vessels in the lungs.

A small opening in the atrial septum allows a small amount of blood to pass through from the left atrium to the right atrium. A large opening allows more blood to pass through and mix with the normal blood flow in the right heart.

The lungs are able to cope with this extra blood flow for a long period of time. In some patients, the extra blood flow eventually raises the blood pressure in the lungs, usually after several decades. This then hardens the blood vessels in the lungs, causing them to be diseased, resulting in irreversible changes in the lungs.

What are the symptoms of an atrial septal defect?

Many children have no symptoms and seem healthy. However, if the ASD is large, permitting a large amount of blood to pass through to the right side of the heart, the right atrium, right ventricle, and lungs will become overworked, and symptoms may be noted. The following are the most common symptoms of atrial septal defect. However, each child may experience symptoms differently. Symptoms may include:

• Child tires easily when playing

• Fatigue

• Sweating

• Rapid breathing

• Shortness of breath

• Poor growth

• Frequent respiratory infections

The symptoms of an atrial septal defect may resemble other medical conditions or heart problems. Always consult your child's physician for a diagnosis.