What is an atrial septal defect?
An atrial septal defect (ASD) 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 can be a congenital (present at birth) heart defect, or it can result from the failure of normal postnatal closure of a hole that is present in the heart of every fetus. 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.
Atrial septal defects occur in a small percentage of 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 usually 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 over two-thirds 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, in the area where the right 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 drain to the right atrium, rather than the left atrium.
- Coronary sinus atrial septal defect. This defect is located within the wall of the coronary sinus, where it passes behind the left atrium. The coronary sinus carries the blood flow from the heart’s own vein, into the right atrium. It is the rarest of all atrial septal defects.
Why is an atrial septal defect a concern?
Over time, this heart defect can 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 permanent changes in the lungs.
What are the symptoms of an atrial septal defect?
Most children have no symptoms and seem healthy. Some infants or small children with other lung problems become symptomatic due to the extra blood flow to the lungs. 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
- 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.
How is an atrial septal defect diagnosed?
Your child’s physician may have heard a heart murmur during a physical examination, and referred your child to a pediatric cardiologist for a diagnosis. In this case, the heart murmur is caused by the extra blood from the ASD flowing through the pulmonary valve.
A pediatric cardiologist specializes in the diagnosis and medical management of congenital heart defects, as well as heart problems that may develop later in childhood. The cardiologist will perform a physical examination, listening to the heart and lungs, and make other observations that help in the diagnosis. The location within the chest that the murmur is heard best, as well as the loudness and quality of the murmur (harsh, blowing, etc.) will give the cardiologist an initial idea of which heart problem your child may have. Diagnostic testing for congenital heart disease varies and is determined by the child’s age and clinical condition. Some tests that may be recommended include the following:
- Chest X-ray. A diagnostic test which uses invisible X-ray beams to produce images of internal tissues, bones and organs onto film. With an ASD, the heart may be enlarged because the right atrium and ventricle have to handle larger amounts of blood flow than normal. Also, there may be changes that take place in the lungs due to extra blood flow that can be seen on an X-ray. Learn more about X-ray.
- Electrocardiogram (ECG or EKG). A test that records the electrical activity of the heart, shows abnormal rhythms (arrhythmias or dysrhythmias), and detects heart muscle stress. Learn more about electrocardiogram.
- Echocardiogram (echo). A procedure that evaluates the structure and function of the heart by using sound waves recorded on an electronic sensor that produce a moving picture of the heart and heart valves. An echo can show the pattern of blood flow through the atrial septal opening, and determine how large the opening is, as well as how much blood is passing through it. Learn more about echocardiogram.
How is an atrial septal defect treated?
Specific treatment for ASD will be determined by your child’s physician based on:
- The child’s age, overall health and medical history
- Extent of the defect
- The child’s tolerance for specific medications, procedures, or therapies
- Expectations for the course of the defect
- The family’s opinion or preference.
Secundum atrial septal defects may close spontaneously as a child grows. Once an atrial septal defect is diagnosed, your child’s cardiologist will evaluate your child periodically to see whether it is closing on its own. Usually, an ASD will be repaired if it has not closed on its own by the time your child starts school—to prevent lung problems that will develop from long-time exposure to extra blood flow. The decision to close the ASD may also depend on the size of the defect. Individuals who have their atrial septal defects repaired in childhood can prevent problems later in life.
- Medical management. Many children have no symptoms, and require no medications. However, in rare circumstances, children may need to take medications to help their heart work better, since the right side is under strain from the extra blood passing through the ASD. Medications may be prescribed, such as diuretics. Diuretics help the kidneys remove excess fluid from the body. This may be necessary because the body’s water balance can be affected when the heart is not working as well as it could.
- Surgical repair. Some children may need their ASD repaired surgically at the Tidwell Procedure Center at CHOC. The repair is performed under general anesthesia and the defect may be closed with stitches or a special patch. Learn more about heart surgery.
- Device closure. Device closure is frequently performed for secundum ASD, depending on the size of the defect and the weight of the child and is performed in CHOC’s state-of-the-art catheterization lab. During this cardiac catheterization procedure, the child is sedated and a small, thin, flexible tube (catheter) is inserted into a blood vessel in the groin and guided to the inside of the heart. Once the catheter is in the heart, the cardiologist will pass a special device, called a septal occluder, into the open ASD, preventing blood from flowing through it. Learn more about cardiac catheterization.
What is the long-term outlook after ASD repair?
The majority of children who have had an atrial septal defect repair can live healthy lives. Your child’s cardiologist may recommend that your child take antibiotics to prevent bacterial endocarditis for a specific time period after discharge from the hospital.
Outcomes also depend on the type of ASD, as well as how early in life the ASD was diagnosed and whether or not it was repaired. With early diagnosis and repair of an ASD, the outcome is generally excellent, and minimal follow-up is necessary. When an ASD is diagnosed later in life, if complications occur after surgical closure, or the ASD is never repaired, the outlook may be worse than normal. There is a risk of developing pulmonary hypertension (high blood pressure in the blood vessels of the lungs). These individuals should receive follow-up care at a center that specializes in congenital heart disease.
Consult your child’s physician regarding the specific outlook for your child.