Atrial Septal Defect (ASD)

What Is Atrial Septal Defect?

An atrial septal defect (ASD) is a hole in the wall (septum) that separates the two upper chambers (atria) of the heart. The defect allows blood to flow from one atrium to the other, usually from the left side to the right side. This causes extra blood flow:

• In the right atrium
• In the right ventricle
• To the lungs

In a normal heart, oxygen-poor (blue) blood returns from the body to the right atrium. From the right atrium, the blue blood flows to the right ventricle—one of the two lower chambers of the heart—and is pumped to the lungs to pick up oxygen. After travelling through the lungs, the blood is now oxygen-rich and red. The red blood returns from the lungs to the left atrium and goes to the left ventricle, where it is pumped to the body. The right and left sides of the heart are normally completely separated by the septum. The septum keeps the blue blood from mixing with the red blood.

ASD is the second most common congenital heart defect.

• More than 3,000 babies are born with ASD each year in the United States.
• ASD occurs twice as often in girls as in boys.

Effects of Atrial Septal Defect

Over time, the extra blood flow to the right side of the heart and the lungs can cause:

• Enlargement of the right atrium and the right ventricle.
• Right heart overload. The right side of the heart has to work harder to pump extra blood to the lungs, especially as resistance in the pulmonary (PULL-mun-ary) artery increases. Over time, the heart may become overworked, and function may become impaired. This is exceedingly rare with modern methods of diagnosis and treatment.
• Irregular heartbeats or rhythms (arrhythmias). Extra blood flowing into the right atrium through the ASD can cause the atrium to stretch and enlarge. When this occurs, a fast heartbeat can develop with symptoms such as dizziness, fainting, or chest discomfort.
• Stroke. Occasionally a blood clot in a vein or in the right side of the heart can pass through the ASD and enter the blood stream, where it can block an artery supplying the brain and cause a stroke.
• Pulmonary artery hypertension. This is when high blood pressure exists in the arteries that carry blood to the lungs. The extra blood being pumped to the lungs can increase the pressure in the pulmonary arteries. Over time, high pressure can damage the arteries and the small blood vessels in the lungs. They thicken and become stiff, making it harder for blood to flow through them (pulmonary vascular disease).

Usually, most of these effects don't show up until adulthood, often around age 30 or later. They are rare in infants and children.

Characteristics

An ASD is classified by its size and location.

Size

The size of an ASD can range from small to large.

• Most small defects close on their own as the heart grows during childhood. They usually allow only a small amount of blood to flow between the atria.
• Moderate to large defects are much less likely to close on their own. They allow two or more times the normal amount of blood to flow through the right side of the heart. Large holes sometimes cause symptoms during infancy or childhood.

Location

Three major types of ASD exist, based on the location of the defect on the septum:

• Secundum. This defect is in the middle of the septum. It is the most common form of ASD. About 7 out of every 10 babies born with ASD have this type. This type often closes on its own, unless it is large.
• Primum. This defect is in the lower part of the septum. It also involves an incomplete or partial atrioventricular septal defect, and the valves that separate the upper and lower heart chambers are not normal. About 2 out of every 10 babies born with ASD have primum defects. This type of defect does not close on its own.
• Sinus venosus. This defect is in the upper part of the septum near where a large vein (the superior vena cava) brings blue blood from the upper body to the right atrium. It is rare, accounting for only about 1 out of every 10 cases of ASD. Children with sinus venosus defects usually have an associated condition called partial anomalous pulmonary venous return, in which one or more of the veins carrying red blood from the lungs return to the wrong chamber of the heart. This type of defect does not close on its own.

Outlook

Half of all ASDs close without treatment. When treatment is necessary, it is usually successful. Once the defect has closed or has been repaired, most children:

• Don't need additional treatment or medicine
• Can live normal, healthy lives

How the Heart Works

Your child's heart is a muscle about the size of his or her fist. It works like a pump and beats about 100,000 times a day.

The heart has two sides. An inner wall, called the septum, separates each side. The right side of the heart pumps blood to the lungs to pick up oxygen. Then, oxygen-rich blood returns from the lungs to the left side of the heart, and the left side pumps the blood to the body.

The heart has four chambers and four valves and is connected to various blood vessels. Veins are the blood vessels that carry blood from the body to the heart. Arteries are the blood vessels that carry blood from the heart to the body.

Heart Chambers

The heart has four chambers or "rooms"—two on the left side of the heart and two on the right.

• The atria are the two upper chambers that collect blood as it comes into the heart.
• The ventricles (VEN-trih-kuls) are the two lower chambers that pump blood out of the heart to the lungs or other parts of the body.

Heart Valves

Four valves control the flow of blood from the atria to the ventricles and from the ventricles into the two large arteries connected to the heart.

• The tricuspid (tri-CUSS-pid) valve is in the right side of the heart, between the right atrium and the right ventricle.
• The pulmonary valve is in the right side of the heart, between the right ventricle and the entrance to the pulmonary artery, which carries blood to the lungs.
• The mitral valve is in the left side of the heart, between the left atrium and the left ventricle.
• The aortic (ay-OR-tik) valve is in the left side of the heart, between the left ventricle and the entrance to the aorta, which is the artery that carries blood to the body.

Valves are like doors that open and close. They open to allow blood to flow through to the next chamber or to one of the arteries, and then they shut to keep blood from flowing backward.

When your heart's valves open and close, they make the familiar "lub-DUB" or "lub-DUPP" sounds that your doctor can hear using a stethoscope.

• The first sound is made by the tricuspid and mitral valves closing at the beginning of systole (SIS-toe-lee). Systole is when the heart contracts, or squeezes, and pumps blood out of the heart.
• The second sound is made by the aortic and pulmonary valves closing at the beginning of diastole (di-AS-toe-lee). Diastole is when the heart relaxes and fills with blood.

Arteries

The arteries are major blood vessels connected to your heart.

• The pulmonary artery carries blood pumped from the right side of the heart to the lungs to pick up a fresh supply of oxygen.
• The aorta is the main artery that carries oxygen-rich blood pumped from the left side of the heart out to the body.
• The coronary arteries are the other important arteries attached to the heart. They carry oxygen-rich blood to the heart muscle, which must have its own blood supply to function.

Veins

The veins are major blood vessels connected to your heart.

• The pulmonary veins carry oxygen-rich blood from the lungs to the left side of the heart so it can be pumped out to the body.
• The vena cavae are two large veins that carry oxygen-poor blood from the body back to the heart.

What Causes Atrial Septal Defect?

There is no single, known cause of atrial septal defect (ASD).

Heredity (genetics) may play a role in ASD. In some cases, it may be due to a difference in one or more genes.

What Are the Signs and Symptoms of Atrial Septal Defect?

The major signs and symptoms of atrial septal defect (ASD) are:

• Heart murmur
• Change in heart sounds that represent valve closure

A heart murmur is the most common sign of ASD. Often, it is the only sign. Sometimes, the heart murmur is the sound from a delay in the closing of the pulmonary valve.

Most children with ASD don't have symptoms, even with a large ASD. However, some children and adults with ASD may develop symptoms which include:

• Fatigue or tiring easily
• Shortness of breath
• Fast breathing
• Sweating
• Slow growth

In most people with ASD who develop symptoms, the symptoms don't develop until adulthood.

How Is Atrial Septal Defect Diagnosed?

Atrial septal defect (ASD) is diagnosed using a medical history, a physical exam, and tests. ASD is usually found in infants or children during a routine physical exam. However, some people with ASD are not diagnosed until adulthood.

Medical and Family History

Your child's doctor will ask you about:

• Family history of congenital heart disease
• Your child's symptoms
• Your child's feeding and growth

Physical Examination

The doctor will listen to your child's heart with a stethoscope for a heart murmur. The doctor will also check for signs of increased blood flow to the lungs.

Tests

Your child's doctor may order one or more tests to diagnose ASD. These tests also help the doctor decide the type and size of the defect:

• Echocardiogram (ultrasound). An echocardiogram of the heart is the test most often used to diagnose ASD. It uses sound waves to take pictures of the heart and shows the movement of blood through the heart. An echocardiogram shows the location and exact size of the ASD. It also shows if the right side of the heart is enlarged and can show if there are other congenital heart defects.
• Chest x ray. A chest x ray takes a picture of the heart and lungs. It can show if the heart is enlarged or if there is fluid in the lungs.
• ECG (electrocardiogram). An ECG test measures the rate and regularity of your child's heartbeat. It provides an estimate of enlargement of the heart chambers and shows abnormal heart rhythms (arrhythmias).
• Cardiac catheterisation. In cardiac catheterisation, a thin flexible tube (catheter) is passed through a blood vessel (artery or vein) to the heart. With the assistance of x rays, the doctor can see the child's blood vessels and heart. During the procedure, the doctor can measure blood pressure in the heart and arteries connected to the heart and see how much blood is mixing between the two sides of the heart. Cardiac catheterisation is rarely used for diagnosis of ASD, unless the echocardiogram does not provide enough information or if other defects or problems are suspected.

How Is Atrial Septal Defect Treated?

The goals of treating atrial septal defect (ASD) include:

• Monitoring the defect to see if it closes by itself (secundum defects only)
• Closing or repairing the ASD to prevent pulmonary vascular disease and other complications
• Treating symptoms of heart failure, if present
• Preventing abnormal heart rhythms

Types of Treatment

Types of treatment include:

• Monitoring and observation (periodic checkups)
• Medicines
• Closure of the ASD through surgery or a procedure using a catheter

Your child's doctor will discuss treatment options with you and will consider your family's preferences when making treatment decisions.

Monitoring and observation

Periodic checkups are done to see if the defect closes on its own. About half of all ASDs close on their own, and many close within the first year of life. Your child's doctor will recommend how often your child should be checked, ranging from weekly checkups to checkups every 1 or 2 years.

Medicines

Children with no symptoms usually don't need any medicines. Children who develop symptoms usually are referred for closure of the defect. They may need medicines to control the symptoms until the defect can be closed. Medicines include:

• Digoxin to improve heart function and keep the heartbeat regular
• Diuretics to treat fluid buildup

Antibiotics may be given to prevent bacterial endocarditis, an infection of the inner lining and valves of the heart. The antibiotic is given in a single dose 1 hour before a dental visit or surgical procedure. This treatment is usually needed for only 6 months after ASD surgery or a catheter procedure. The antibiotics are used only to prevent infection and not to treat the ASD.

Closure of the atrial septal defect

Closure may be recommended for infants and children who develop symptoms such as fast breathing or slow growth. Closure is also commonly performed for children with moderate to large ASDs that remain at 3 to 5 years of age. Sometimes, doctors recommend closure of smaller defects found in older children and adults.

Surgery

• The surgeon makes an incision down the center of the chest to reach the ASD.
• The child is placed on a heart/lung bypass machine during surgery.
• The heart is stopped, and the heart/lung bypass machine takes over for the heart, pumping red blood throughout the body.
• The heart/lung machine also brings blue blood back to the machine, where it picks up oxygen.
• The surgeon uses a special patch or stitches to close the ASD.
• The surgeon puts the patch over the ASD and sews it into place.
• Once the repair is completed, the heart is restarted.
• The child is taken off the heart/lung bypass machine.
• The surgeon then closes the skin incision.

Complications, such as bleeding and infection, from ASD surgery are rare and short term. Some people may develop swelling of the outer lining of the heart, causing fluid to collect around the heart. This usually resolves with medicine.

Your child may need to take medicine temporarily to help with discomfort.

After surgery. After ASD surgery, your child will spend a few days in the intensive care unit or in a regular hospital room. Most children go home within 4 days after the surgery.

While in the hospital, your child will be given medicines to reduce pain or anxiety as needed. The doctors and nurses at the hospital will teach you how to care for your child at home. They will talk to you about:

• Avoiding blows to the chest incision as it heals
• Limiting activity for your child while he or she recovers
• Bathing
• Returning to school
• Scheduling followup appointments with your child's doctors
• Administering medicine to your child at home, if needed

Results. The outlook for children after surgery is usually excellent. Your child will most likely have little pain or discomfort from the incision. After recovering, your child should be able to take part in normal activities.

Procedures using catheters

A procedure that uses a catheter to close the ASD with a special closure device (septal occluder) is a recent but increasingly used option. Catheters are thin, flexible tubes used in cardiac catheterisation.

The advantages of such procedures are that they:

• Don't require the child's chest to be opened
• Usually require no more than an overnight stay in hospital
• Let the child recover quickly

Closure with a catheter can't be done for every type of ASD. A catheter can be used with secundum defects (that is, those located near the middle of the septum). It can't be used with defects so large that there is not enough surrounding tissue to anchor the device.

The catheter procedure is done under general anaesthesia, so your child will sleep through the procedure and not feel any discomfort. During the procedure, the doctor:

• Inserts a catheter into a blood vessel in the groin
• Threads the catheter to the heart
• Measures pressure and oxygen levels for all four heart chambers
• Injects dye and takes pictures (angiogram) of the heart
• Uses a balloon catheter (under ultrasound guidance) to estimate the size of the ASD
• Threads a special fabric-covered wire frame to the heart
• Positions half of the device on the left side of the atrial septum
• Positions the other half of the device on the right side of the atrial septum
• Wedges ASD between the two parts of the device

Within 6 to 8 weeks, normal tissue grows in and over the device. There is no need to replace the closure device as the child grows.

Results. The outlook for children having this procedure is excellent. Closures are successful in more than 9 out of 10 patients, with no significant leakage. Because the device is relatively new, what is not known is whether there are any long-term problems with the device compared to surgery.

Living With Atrial Septal Defect

Smaller atrial septal defects (ASDs) often close on their own, and children don't have any problems or need treatment. Children and adults with small ASDs that cause no symptoms may be healthy and feel well with no treatment. However, many others undergo closure procedures to prevent potential long-term complications. Most children recover well from closure procedures and live normal, healthy lives. Adults also usually do well after closure procedures.

Medical Needs

Arrhythmias. The risk of arrhythmias (irregular heartbeats) increases before and after surgery. Adults older than 40 years are especially likely to have arrhythmias. People who had arrhythmias before surgery are more likely to have them after surgery.

Followup care. Regular followup care is advised for those who had:

• ASD repaired as an adult
• Arrhythmias before and after surgery
• ASD repaired with a procedure using catheters instead of surgery
• High blood pressure in the pulmonary artery at the time of surgery

Special Needs for Children

Activity. Children with a repaired or closed ASD have no restrictions on their activity. Children who are being monitored and treated with medicines may have some restrictions. Consult your child's doctor for activity guidelines.

Growth and development. Children with ASD have very few growth and development problems. If your child has slow growth, he or she will catch up after the ASD has closed or been repaired.

Antibiotics before dental care. Children with just ASD don't need antibiotics for dental care. The doctor may recommend antibiotics for dental care for the first 6 months after a closure procedure. The antibiotic is given in a single dose 1 hour before the dental visit. The antibiotic is given to prevent bacteria from entering the bloodstream and causing an infection called endocarditis.

Regular health care. Your child should see his or her regular doctor for routine health care.

Special Needs for Adults

Some adults have their ASDs closed to prevent or minimize symptoms and complications. After ASD closure, full recovery takes longer for adults than for children. You may benefit from a cardiac rehabilitation programme as you recover from your ASD closure. Talk with your doctor about when it is all right for you to drive, return to work, resume exercising, and do other activities.

Key Points

• An atrial septal defect (ASD) is a hole in the wall (septum) that separates the two upper chambers (atria) of the heart. It is a type of congenital heart defect. The cause is not known.
• An ASD lets blood flow from one atrium to the other, usually from the left atrium to the right atrium. This causes some red blood to mix with the blue blood that is pumped to the lungs.
• An ASD can have several effects over time, including enlargement of the right atrium and the right ventricle, damage to the arteries and blood vessels in the lungs, and irregular heartbeats or rhythms (arrhythmias).
• ASDs can range from very small holes to large ones. They are classified based on location of the hole in the atrial septum.
• The most common type of ASD is a secundum defect, which affects the middle part of the septum. Other types are primum defects and sinus venosus defects.
• A heart murmur is often the only sign of an ASD. Some children and adults with an ASD develop other signs and symptoms.
• About half of all ASDs close on their own and don't require treatment.
• The main test used to diagnose ASD is the echocardiogram.
• ASDs that don't close on their own can often be closed through surgery or a catheter procedure. Closure is usually successful with excellent long-term results.
• Most children live normal, healthy lives after ASD closure.
• When ASD closure can't be done, medicines are used to treat symptoms.