Atrial septal defects (ASDs) are a group of rare disorders of the heart that are present at birth (congenital) and involve a hole in the wall (septum) that separates the two upper-chambers (atria) of the heart. Small atrial septal defects may close on their own during infancy or early childhood.
Normally the heart has four chambers: two upper chambers known as atria that are separated from each other by a fibrous partition known as the atrial septum and two lower chambers known as ventricles that are separated from each other by the ventricular septum. Valves connect the atria (left and right) to their respective ventricles. A small opening between the two atria (foramen ovale) is present at birth. Shortly after birth, the atrial septum gradually grows and seals this opening. In infants with atrial septal defects, the atrial septum may not close properly or may be malformed during fetal development. In these disorders, the opening (called patent foramen ovale) between the atria persists long after it should be closed, resulting in an increase in the workload on the right side of the heart and excessive blood flow to the lungs.
Initially, the symptoms associated with atrial septal defects may be absent or so mild that they may go unnoticed. Frequently this disorder is not recognized until school age or even adulthood. In adults with undetected atrial septal defects, various respiratory problems and/or heart failure may develop. An adult who has had an undetected atrial septal defect for decades may have a shortened life span from heart failure or high blood pressure that affects the arteries in the lungs (pulmonary hypertension). Surgery may be necessary to repair atrial septal defects to prevent complications.
Several forms of atrial septal defects are recognized. They are classified according to their location in the septum. The term primum refers to defects that are in the lower part of the septum. The term secundum refers to defects that are located in the middle of the septum, and the term sinus venosus refers to defects in the upper part of the septum.
Subdivisions of Atrial Septal Defects:
- Ostium Primum Defect (endocardial cushion defects included)
- Ostium Secundum Defect
- Sinus Venosus
- Coronary sinus
Ostium Primum Defect:
Ostium primum atrial septal defect is less common. The lower part of the atrial septum fails to develop normally, leaving an opening between the atria. Frequently, the valves that separate the atria from their respective ventricles (tricuspid and mitral) are also malformed, and the septum that divides the ventricles may also be deficient or malformed (atrioventricular septal defect). Another defect may have occurred during embryonic development in the tissue that forms the septum that divides the heart into atria and ventricles (endocardial cushion defect).
Ostium Secundum Defect:
Ostium secundum atrial septal defect is the most common form of this group of heart defects. The middle portion of the atrial septum in the region of the foramen ovale fails to close during fetal development. The size of the opening may vary, along with the severity of the symptoms.
Sinus venosus, the least common form of atrial septal defect, occurs when there is an opening on the upper portion of the atrial septum. This defect is often associated with malformations of the vein that leads from the lungs into the heart (right pulmonary vein). One of the major veins of the body that returns blood to the heart (superior vena cava) may also be malformed.
In this rare defect, part of the wall between the coronary sinus — which is part of the vein system of the heart — and the left atrium is missing.
Most children with atrial septal defects have no symptoms. A few affected individuals may be abnormally thin and experience mild growth delays as well as an increased susceptibility to respiratory infections. Other very severely affected children, especially those with ostium primum defects, may experience breathlessness, easy fatigability with exercise, and/or irregular heartbeats (arrhythmias).
A heart murmur is the most common sign and usually the only sign of ASD in children. There may also be a change in heart sounds that represents the closing of the valves of the heart.
Around the age of 40 years, people with atrial septal defects may experience symptoms related to an increase in pressure in the blood vessels of the lungs (pulmonary hypertension). Increased pressure in these vessels causes the blood to be propelled or "shunted" through the abnormal opening in the heart. Symptoms may include a bluish discoloration of the skin (cyanosis), clubbing of the fingertips, exercise intolerance, and/or an abnormal increase in the number of circulating red blood cells (polycythemia). Abscesses may also develop in the brain. Other symptoms may include swelling of the arms and legs and/or difficulty breathing.
Severe cases of atrial septal defects may lead to life-threatening complications such as chest pain, irregular heartbeats (arrhythmias), abnormal enlargement of the heart, a "fluttering" of the heart (atrial fibrillation), and/or heart failure. Females with atrial septal defects who become pregnant may be at risk for episodes of blood clot formation. These clots may detach from the walls of the blood vessels and travel through the systemic circulation (embolism).
Most cases of atrial septal defects occur on their own for no apparent reason (sporadically). The exact nature of the developmental defect or defects that may occur during embryonic development (embryogenesis) remain unclear. Genetics and environmental factors may play a role.
Some cases of ASD appear to run in families. In such rare cases, the two forms, ostium primum and ostium secundum defects seem to be inherited as autosomal dominant genetic traits. To complicate matters further, genetic analysis suggests that there are at least two different genetic disorders involving ASD that are linked to mutations in a gene called NKX2-5.
It's not known why atrial septal defects occur, but congenital heart defects appear to run in families and sometimes occur with other genetic problems, such as Down syndrome. If you have a heart defect, or you have a child with a heart defect, a genetic counselor can estimate the odds that any future children will have one.
Some conditions that you have or that occur during pregnancy may increase your risk of having a baby with a heart defect, including:
- Rubella infection. Becoming infected with rubella (German measles) during the first few months of your pregnancy can increase the risk of fetal heart defects.
- Drug, tobacco or alcohol use, or exposure to certain substances. Use of certain medications, tobacco, alcohol or drugs, such as cocaine, during pregnancy can harm the developing fetus.
- Diabetes or lupus. If you have diabetes or lupus, you may be more likely to have a baby with a heart defect.
- Obesity. Being extremely overweight (obese) may play a role in increasing the risk of having a baby with a birth defect.
- Phenylketonuria (PKU). If you have PKU and aren't following your PKU meal plan, you may be more likely to have a baby with a heart defect.
Echocardiogram: This is the most commonly used test to diagnose an atrial septal defect. Some atrial septal defects are found during an echocardiogram done for another reason.
In echocardiography, sound waves are used to produce a video image of the heart. It allows your doctor to see your heart's chambers and measure their pumping strength. This test also checks heart valves and looks for any signs of heart defects. Doctors may use this test to evaluate your condition and determine your treatment plan.
Chest X-ray: An X-ray image helps your doctor to see the condition of your heart and lungs. An X-ray may identify conditions other than a heart defect that may explain your signs or symptoms.
Electrocardiogram (ECG): This test records the electrical activity of your heart and helps identify heart rhythm problems.
Cardiac catheterization: In this test, a thin, flexible tube (catheter) is inserted into a blood vessel at the groin or arm and guided to your heart. Through catheterization, doctors can diagnose congenital heart defects, test how well your heart is pumping and check the function of your heart valves. Using catheterization, the blood pressure in your lungs also can be measured.
However, this test usually isn't needed to diagnose atrial septal defect. Doctors may also use catheterization techniques to repair heart defects.
Magnetic resonance imaging (MRI): MRI is a technique that uses a magnetic field and radio waves to create 3-D images of your heart and other organs and tissues within your body. Your doctor may request an MRI if echocardiography can't definitively diagnose an atrial septal defect.
Computerized tomography (CT) scan: A CT scan uses a series of X-rays to create detailed images of your heart. A CT scan may be used to diagnose an atrial septal defect if echocardiography hasn't definitely diagnosed an atrial septal defect.
Many atrial septal defects close on their own during childhood. For those that don't close, some small atrial septal defects don't cause any problems and may not require any treatment. But many persistent atrial septal defects eventually require surgery to be corrected.
If your child has an atrial septal defect, your child's cardiologist may recommend monitoring it for a period of time to see if it closes on its own. Your child's doctor will decide when your child needs treatment, depending on your child's condition and whether your child has any other congenital heart defects.
Medications won't repair the hole, but they may be used to reduce some of the signs and symptoms that can accompany an atrial septal defect. Drugs may also be used to reduce the risk of complications after surgery. Medications may include those to keep the heartbeat regular (beta blockers) or to reduce the risk of blood clots (anticoagulants).
Many doctors recommend repairing an atrial septal defect diagnosed during childhood to prevent complications as an adult. Doctors may recommend surgery to repair medium- to large-sized atrial septal defects. However, surgery isn't recommended if you have severe pulmonary hypertension.
For adults and children, surgery involves plugging or patching the abnormal opening between the atria. Doctors will evaluate your condition and determine which procedure is most appropriate. Atrial septal defects can be repaired using two methods:
Cardiac catheterization. In this procedure, doctors insert a thin tube (catheter) into a blood vessel in the groin and guide it to the heart using imaging techniques. Through the catheter, doctors set a mesh patch or plug into place to close the hole. The heart tissue grows around the mesh, permanently sealing the hole.
This type of procedure may be performed to repair secundum atrial septal defects. Some large secundum atrial septal defects may not be able to be repaired through cardiac catheterization, and may require open-heart surgery.
Open-heart surgery. This type of surgery is done under general anesthesia and requires the use of a heart-lung machine. Through an incision in the chest, surgeons use patches to close the hole. This procedure is the preferred treatment for certain types of atrial septal defects (primum, sinus venosus and coronary sinus), and these types of atrial defects can only be repaired through open-heart surgery.
This procedure may also be conducted using small incisions (minimally invasive surgery) for some types of atrial septal defects.
Doctors use imaging techniques after the defect has been repaired to check the repaired area.
Follow-up care depends on the type of defect and whether other defects are present. For simple atrial septal defects closed during childhood, only occasional follow-up care is needed.Adults who've had atrial septal defect repair need to have regular follow-up appointments to check for complications, such as pulmonary hypertension, arrhythmias, heart failure or valve problems.
- Mayo Clinics