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Atrial Septal Defect


What is an atrial septal defect?
An atrial septal defect (ASD) is an opening in the wall between the two top chambers of the heart: the right atrium and the left atrium. It is one of the most common types of congenital heart defects, comprising approximately 10%, and is more common in females than males.

When does it develop?
The atrial septum forms between the 4th and 5th week of life. At some point during this period of time there is a failure of portions of the wall to fully fuse together. The defect can vary in its location on the atrial septum, and this location is used to classify the ASD by type. The most common type is known as a secundum atrial septal defect, and is located in the middle of the atrial septum.

How does it affect the heart?
The atrial septal defect provides a communication between the right and the left atria. This allows blood to flow across the opening from the left atrium to the right atrium causing an increased volume of blood to be delivered to the right side of the heart, and subsequently to the lungs. Because it is receiving so much extra blood, the right side of the heart does more than its normal share of work. Over time, this extra blood volume can lead to enlargement of the right atrium and the right ventricle, decreased function of the right ventricle (due to volume overload), high pressures in the lungs (due to excess blood flow), and abnormalities of heart rhythm (due to the stretching and enlargement of the right atrium).

The effects on the heart and the development of symptoms are often directly related to the size of the ASD and the respective pressures in the heart. Some defects are very small and produce no symptoms. Larger sized defects can produce varying types of symptoms at all points across the life span.

What are the symptoms?
Atrial septal defects diagnosed in childhood are often fairly large and produce symptoms of breathlessness and exercise intolerance. The excess of blood crossing the ASD to the right side of the heart and lungs can lead to signs and symptoms of heart failure. The child generally requires surgical intervention before starting school.

Atrial septal defects are often not diagnosed until the second or third decade of life, and sometimes later. Symptoms can be subtle, and include fatigue, decreased exercise tolerance, breathlessness and palpitations. If untreated, heart failure symptoms and elevated pressure in the lungs can result. Often the diagnosis is made by the patient's primary care physician, or sometimes by an obstetrician when a cardiac murmur is noted during the routine pregnancy exam. More rarely, the diagnosis can be made following a stroke in which a small clot in the legs travels across the hole and lodges in the brain.


How is an ASD diagnosed?
If a physician suspects an atrial septal defect (for example, on the basis of a cardiac murmur or abnormal ECG), many diagnostic tests are available for further evaluation. The most common diagnostic test is the echocardiogram, or an ultrasound of the heart. It is painless, non invasive, and highly accurate for detecting and evaluating ASDs. Other methods include special xrays such as cardiac MRI or cardiac CT. Finally, an invasive procedure known as a cardiac catheterization is done in a hospital and permits direct measurement of the ASD size as well as the pressures and oxygen content inside the heart chambers.


What types of treatment are available for ASDs?
Many adults with small ASDs require no treatment other than routine cardiology follow up, with echocardiograms every few years to reevaluate the heart size and function.  A daily aspirin is sometimes recommended in order to reduce the risk of blood clot formation in the veins. Patients are advised to practice good leg care by avoiding prolonged crossing of the legs, standing and stretching the legs on long trips or long workdays, and walking regularly for exercise.

Symptoms produced by larger ASDs, such as palpitations or breathlessness may need to be treated with medications, and ultimately with a method to close the communication and eliminate the extra blood volume load to the right side of the heart and lungs. 

Surgical intervention is the preferred method for atrial septal defects that are not located in the middle of the atrial septum (e.g. the secundum type). These other types are known as primum ASDs if located near the bottom of the septum, and sinus venosus ASDs if located near the top of the septum. The sinus venosus ASD is often associated with abnormal location of one or more pulmonary veins (blood vessels that return blood with oxygen to the left side of the heart).  Very large secundum ASDs may also need to be surgically repaired.  Open heart surgery and cardiopulmonary bypass are utilized, followed by a short hospital stay.
Secundum ASDs that are of an appropriate size and location may now be closed via catheter methods using various devices, the most common of which is the Amplatzer septal occluder device. The device consists of a wire mesh made of nickel and titanium (Nitinol). The wire mesh is filled with polyester fabric to help close the defect. In the catheterization lab with the patient under anesthesia, the doctor carefully measures the size of the ASD. The appropriate sized device is then attached to a cable, inserted into a special catheter and threaded up into the heart via a vein in the groin. It is then pushed out the catheter until one of the device discs is on the left side of the hole and the other disc is on the right side of the hole. When the doctor is satisfied with the device position, the clamp is released and the device sits securely in place. Eventually, the body's own tissue will grow over the device, incorporating it into the atrial septum.  The patient is usually able to go home the following day, and can return to his or her usual activities within a few days after that.

What are the short and long term issues associated with repair of an ASD?
Short term issues for surgically repaired ASDs include a follow up visit with the cardiac surgeon approximately  one week after the procedure to make sure that the healing process is satisfactory. Patients after cardiac surgery are usually able to resume work duties after about 6-8 weeks. You should follow up with your cardiologist one month after the surgery for a physical examination, review of medications and possibly an echocardiogram.

Short term issues for catheter repaired ASDs include an echocardiogram the day following the procedure and at one month post procedure. Some type of blood thinner will be required, and this is usually aspirin and/or Plavix. Our institution recommends no heavy lifting or strenuous exercise for one month. We also recommend deferring any elective dental procedures for 6 months following the Amplatzer procedure.

Long term issues for successfully repaired ASDs, either surgically or via catheter, involve regular visits to your ACHD cardiologist for physical examination and annual echocardiogram for the first few years after closure. In general, enlarged heart chambers will decrease in size, though they may not completely normalize in all cases. Cardiac function, if decreased, should improve, but this must be followed closely by your doctor. Medications may be able to be weaned or discontinued, but this is individualized and may not apply to every patient; some may still require drugs to treat decreased pump function or abnormal heart rhythms.

Is pregnancy possible after ASD repair?
Women with small unrepaired ASDs as well as women who have undergone successful ASD closures are usually able to tolerate a pregnancy very well, and at low risk. However, family planning should be discussed with your Adult Congenital Heart team in advance of becoming pregnant so that any individual issues such as decreased heart function or abnormal heart rhythms can be incorporated into the overall risk profile. This will allow for a management strategy to enable the pregnancy to proceed safely and successfully.

What forms of exercise are safe?
exercise are considered safe and desirable for patients with atrial septal defects, including surgically or catheter repaired, or small unrepaired defects. This includes walking, jogging, swimming, cycling and elliptical training. Yoga is acceptable, as is light weight training.  Heavy weight lifting should be avoided. Warming up and cooling down before and after exercise, staying well hydrated, and proceeding at a comfortable pace with gradual buildup of activity are all very important, particularly if you have not been exercising regularly for some time.

Will I need to take antibiotics before seeing the dentist?
Following ASD repair, antibiotics are not usually required prior to dental procedures or exams. However, you should check with your doctor to make sure that there are no additional heart problems or concerns apart from your ASD that would warrant antibiotic prophylaxis prior to seeing the dentist.