Atrial Septal Defect (ASD) in Children
Basics of Atrial Septal Defect
The heart has two sides, separated by an inner wall called the septum. A hole in the septum between the heart’s two upper chambers (or “atria”) is called an atrial septal defect. This congenital (present at birth) heart defect occurs when normal heart development is disrupted during the first eight weeks of pregnancy.
An atrial septal defect allows blood to pass from the left side of the heart to the right side. Thus, oxygen-rich (red) blood mixes with oxygen-poor (blue) blood, and some oxygen-rich blood is pumped to the lungs instead of the body.
There are four major types of atrial septal defects:
- Ostium secundum atrial septal defect. The most common variety, it affects about 70 percent of children with the condition. It occurs when a part of the atrial septum fails to close completely while the heart is developing, causing 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 junction of the superior vena cava and right atrium, where the pulmonary veins enter the heart. As a result, the drainage of one or more of the pulmonary veins may be abnormal, with the pulmonary veins entering the right atrium versus the left atrium.
- Coronary sinus atrial septal defect. This defect is located within the coronary sinus, the structure in the right atrium where all of the heart's own veins drain into the right atrium. It is the rarest type of ASD.
Fast Facts of Atrial Septal Defects
- Atrial septal defects occur in 6 percent to 8 percent of all children born with congenital heart disease.
- For unknown reasons, girls have atrial septal defects twice as often as boys.
Causes of Atrial Septal Defects
The heart forms during the first eight weeks of pregnancy. The heart begins as a hollow tube. As the heart develops, it partitions, creating a wall (or “septum”) dividing the two sides of the heart. Atrial septal defects occur when this partitioning process does not complete, thus leaving a hole in the atrial septum.
Heredity may play a role in some congenital heart defects like ASD. Gene defects, chromosome abnormalities and environmental exposure can cause heart problems to occur more often in certain families. Most atrial septal defects occur by chance (or sporadically) with no clear cause. Scientists continue to search for the causes of congenital heart defects like ASD.
Symptoms of Atrial Septal Defects
Many babies born with ASDs have no signs or symptoms. However, as they grow, these children may be small for their age. If the ASD is large and permits a lot of extra blood flow to the right side of the heart, the right atrium, right ventricle and lungs will become overworked, and it may cause symptoms. While each child may experience symptoms of ASD differently, common signs include:
- Tiring easily when playing
- Rapid breathing
- Shortness of breath
- Poor growth
- Frequent respiratory infections
Because the symptoms of an atrial septal defect may resemble other medical conditions or heart problems, it is important to consult with a child's physician for a diagnosis.
Health Problems Associated with Atrial Septal Defect
If a large ASD is not repaired, it can damage the heart and lungs and possibly cause heart failure (which generally doesn’t occur until adulthood) and/or irreversible lung damage.
Tests, Procedures and Diagnosis of Atrial Septal Defect
When a child's physician hears a heart murmur during a physical examination, the physician may refer the child to a pediatric cardiologist, who specializes in the diagnosis and treatment of congenital heart defects and heart problems that may develop later in childhood. In making a diagnosis, the cardiologist performs a physical examination, listens to the heart and lungs and makes other observations. Heart murmurs are evaluated on the basis of pitch, loudness and duration, which give the cardiologist an initial idea of which heart problem a child may have. Diagnostic testing for congenital heart disease varies by a child's age and clinical condition and may include:
- Chest X-ray. This diagnostic test uses X-ray beams to produce images onto film of internal tissues, bones and organs. When a child has an ASD, the heart may be enlarged because the right atrium and ventricle must handle a larger than normal amount of blood flow. Also, changes in the lungs due to extra blood flow may be seen on an X-ray.
- Electrocardiogram (ECG or EKG). This test records the electrical activity of the heart, shows abnormal rhythms (arrhythmias or dysrhythmias) and detects heart muscle stress.
- Echocardiogram (or “echo”). This procedure uses sound waves recorded on an electronic sensor to produce a moving picture of the heart and its valves. An echo can show the pattern of blood flow through the atrial septal opening and determine the opening’s size as well as how much blood is passing through it.
- Cardiac catheterization. This invasive procedure gives very detailed information about the structures inside the heart. Under sedation, a small, thin, flexible tube (catheter) is inserted into a blood vessel in the groin, and gently guided to the inside of the heart. Blood pressure and oxygen measurements are taken in the four chambers of the heart, pulmonary artery and aorta. In addition, contrast dye is injected to more clearly visualize the structures inside the heart. Although an echocardiogram often provides enough diagnostic information, device closure of the ASD can be performed at the time of the catheterization.
Treatment for Atrial Septal Defects
A physician decides the best course of treatment for ASD based on:
- A child's age, overall health and medical history
- Severity of the disease
- A child's tolerance for specific medications, procedures or therapies
- Expectations for the course of the disease
- Parents’ opinions or preferences
Some ASDs spontaneously close as a child grows. Once a child is diagnosed with an atrial septal defect, the child’s cardiologist will evaluate the child periodically to see if it is closing on its own. If not, the cardiologist may recommend that the ASD be repaired by the time the child starts school to prevent lung problems that develop from long-term exposure to extra blood flow. The size of the defect also factors into the decision to close an ASD. Individuals whose atrial septal defects were repaired in childhood can prevent problems later in life.
Medical Management of Atrial Septal Defects
Many children have no symptoms and require no medications. However, some children may need medications to help the heart work better because the extra blood passing through the ASD places a strain on the heart’s right side. Medications that may be prescribed include:
- Digoxin. It helps strengthen the heart muscle, enabling it to pump more efficiently.
- Diuretics. The body's water balance can be affected when the heart is not working as well as it could. These medications help the kidneys remove excess fluid from the body.
Infection Control in Children with Atrial Septal Defects
Children with certain heart defects are at risk for developing an infection of the inner surfaces of the heart known as bacterial endocarditis. It is important that parents inform all medical personnel that their child has an ASD so it can be determined if antibiotics are necessary before a procedure.
Surgical Repair of Atrial Septal Defects
A child's ASD may be repaired during surgery while under general anesthesia. The defect may be closed with stitches or a special patch.
Atrial Septal Defects Device Closure
Device closure is frequently performed for secundum ASD, depending on the size of the defect and weight of the child. 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 gently guided to the inside of the heart. Once the catheter is in the heart, the cardiologist passes a special device (called a “septal occluder”) into the open ASD and prevents blood from flowing through it.