Pediatric Atrial Septal Defect (ASD)

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?

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.

How are arrhythmias diagnosed?

In addition to a complete medical history and physical examination of your child, there are several different types of procedures that may be used to diagnose arrhythmias. Some of these procedures include the following:

• Electrocardiogram (ECG or EKG). An electrocardiogram is a measurement of the electrical activity of the heart. By placing electrodes at specific locations on the body (chest, arms, and legs), a picture, or tracing, of the electrical activity can be obtained as the electrical activity is received and interpreted by an ECG machine. An ECG can indicate the presence of arrhythmias or other types of heart conditions. There are several variations of the ECG test, including the following:
  
  • Resting ECG. For this procedure, the clothing on the upper body is removed and small, sticky patches called electrodes are attached to the chest, arms, and legs. These electrodes are connected to the ECG machine by wires. The ECG machine is then started and records the heart's electrical activity for a minute or so. The child is lying down during this ECG.
  • Exercise ECG, or stress test. The child is attached to the ECG machine as described above. However, rather than lying down, the child exercises by walking on a treadmill or pedaling a stationary bicycle while the ECG is recorded. This test is done to assess changes in the ECG during stress such as exercise.
• Holter monitor. An ECG recording done over a period of 24 or more hours. Three electrodes are attached to the child's chest and connected to a small, portable ECG recorder by lead wires. The child goes about his or her usual daily activities (except for activities such as taking a shower, swimming, or any activity causing an excessive amount of sweating which would cause the electrodes to become loose or fall off) during this procedure. There are two types of Holter monitoring, including the following:
  
  • Continuous recording
  • The ECG is recorded continuously during the entire testing period.
  • Event monitor, or loop recording
  • The ECG is recorded only when the patient starts the recording when symptoms are felt or when an abnormal rhythm is detected.
• Holter monitoring may be done when an arrhythmia is suspected but not seen on a resting ECG. Arrhythmias may be short-lived in nature and not seen during the shorter recording times of the resting ECG.
• Electrophysiologic study (EPS). An invasive test in which a small, thin tube (catheter) is inserted in a large blood vessel in the leg or arm and advanced to the heart. This gives the doctor the capability of finding the site of the arrhythmia's origin within the heart tissue, thus determining how to best treat it. Another procedure called an esophageal electrophysiologic study may be ordered where a soft, thin flexible plastic tube is inserted in the nostril and placed in the esophagus (close to the atria) to provide a more precise ECG recording.
• Tilt table test. A test recommended for children who have frequent fainting (syncope) episodes. The test displays how the heart rate and blood pressure respond to a change in position--lying down to standing up. During this test, medication may be given intravenously to help prevent a fainting episode once the cause has been identified by the doctor.

Treatment for atrial septal defect

Specific treatment for ASD will be determined by your child's physician based on:

• Your child's age, overall health, and medical history

• Extent of the disease

• Your child's tolerance for specific medications, procedures, or therapies

• Expectations for the course of the disease

• Your 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.

Treatment may include:

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

Your child's ASD may be repaired surgically in the operating room. The surgical repair is performed under general anesthesia. The defect may be closed with stitches or a special patch.

Device closure

Device closure is frequently performed for secundum ASD, depending on the size of the defect and the weight of the child. During the 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.

Post-procedure care

Device closure procedure

When the procedure is complete, the catheter(s) will be withdrawn. Several gauze pads and a large piece of medical tape will be placed on the site where the catheter was inserted to prevent bleeding. In some cases, a small, flat weight or sandbag may be used to help keep pressure on the catheterization site and decrease the chance of bleeding. If blood vessels in the leg were used, your child will be told to keep the leg straight for a few hours after the procedure to minimize the chance of bleeding at the catheterization site.

Your child will be taken to a unit in the hospital where he or she will be monitored by nursing staff for several hours after the test. The length of time it takes for your child to wake up after the procedure will depend on the type of medicine given to your child for relaxation prior to the test, and also on your child's reaction to the medication.

After the procedure, your child's nurse will monitor the pulses and skin temperature in the leg or arm that was used for the procedure.

Your child may be able to go home after a specified period of time, providing he or she does not need further treatment or monitoring. You will receive written instructions regarding care of the catheterization site, bathing, activity restrictions, and any new medications your child may need to take at home.

Surgical repair

In most cases, children will spend time in the intensive care unit (ICU) for several hours, or overnight, after an ASD repair. During the first several hours after surgery, your child will most likely be drowsy from the anesthesia that was used during the operation, and from medications given to relax him or her and to help with pain. As time goes by, your child will become more alert.
While your child is in the ICU, special equipment will be used to help him or her recover, and may include the following:

• Ventilator. A machine that helps your child breathe while he or she is under anesthesia during the operation. A small, plastic tube is guided into the windpipe and attached to the ventilator, which breathes for your child while he or she is too sleepy to breathe effectively on his or her own. Many children have the ventilator tube removed right after surgery, but some other children will benefit from remaining on the ventilator for a few hours afterwards, or overnight, so they can rest.

• Intravenous (IV) catheters. Small, plastic tubes inserted through the skin into blood vessels to provide IV fluids and important medications that help your child recover from the operation.

• Arterial line. A specialized IV placed in the wrist, or other area of the body where a pulse can be felt, that measures blood pressure continuously during surgery and while your child is in the ICU.

• Nasogastric (NG) tube. A small, flexible tube that keeps the stomach drained of acid and gas bubbles that may build up during surgery.

• Urinary catheter. A small, flexible tube that allows urine to drain out of the bladder and accurately measures how much urine the body makes, which helps determine how well the heart is functioning. After surgery, the heart will be a little weaker than it was before; the body may start to hold onto fluid, causing swelling and puffiness. Diuretics may be given to help the kidneys remove excess fluids from the body.

• Chest tube. A drainage tube may be inserted to keep the chest free of blood that would otherwise accumulate after the incision is closed. Bleeding may occur for several hours, or even a few days after surgery.

• Heart monitor. A machine that constantly displays a picture of your child's heart rhythm, and monitors heart rate, arterial blood pressure, and other values.

Your child may need other equipment, not mentioned here, to provide support while in the ICU, or afterwards. The hospital staff will explain all of the necessary equipment to you.

Your child will be kept as comfortable as possible with several different medications; some of which relieve pain and some of which relieve anxiety. The staff may also ask for your input as to how best to soothe and comfort your child.

After discharge from the ICU, your child will recuperate on another hospital unit for a few days before going home. You will learn how to care for your child at home before your child is discharged. Your child may need to take medications for a while and these will be explained to you. The staff will provide instructions regarding medications, activity limitations, and follow-up appointments before your child is discharged.

Care for your child at home following ASD repair

Most children feel comfortable when they go home, and have a fair tolerance for activity. Your child may become tired quicker than before the repair, but usually will be allowed to play with supervision, while avoiding blows to the chest that might cause injury to the incision or breastbone. Within a few weeks, your child should be fully recovered and able to participate in normal activity.

Pain medications, such as acetaminophen or ibuprofen, may be recommended to keep your child comfortable at home. Your child's physician will discuss pain control before your child is discharged from the hospital.

Long-term outlook after ASD repair

The majority of children who have had an atrial septal defect repair will 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) or Eisenmenger's syndrome. 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.