An atrial septal defect (ASD) is a hole in the “wall” (called the septum) that separates the heart’s two upper chambers (the atria). ASDs are the second most common type of congenital heart defect.
A hole in the atrial wall (patent foramen ovale, or PFO) is normal before and immediately after birth. In most babies, the hole closes within hours or months of birth. Smaller ASDs tend to more readily close by themselves. Larger ASDs often will persist into adulthood unless treated.
A hole in the septum allows blood to cross from the heart’s left atrium to the right atrium. When this happens, blood that has just returned to the left atrium from picking up oxygen in the lungs will cross to the right atrium. From there, it again returns to the lungs without first traveling through the body. The result is inefficient blood circulation and an increased amount of blood going to the right side of the heart and lungs.
If the ASD is small, blood flow into the right side of the heart and lungs may not be significantly increased. Larger holes, though, can allow much more blood to flow to the right heart and lungs, leading to enlargement of the right-sided heart chambers. This may result in the development of abnormal heart rhythms (arrhythmias), abnormal elevation in the blood pressure in the lung arteries (pulmonary hypertension), and in some cases symptoms of congestive heart failure.
Signs and symptoms of ASD may not occur until adulthood – often age 30 or older – after damage to the heart and lungs has occurred.
Patients with ASD may have some, all, or none of the following symptoms:
- Shortness of breath
- Swelling (legs, feet, abdomen)
- Palpitations or irregular beats of the heart
- Poor weight gain in children
ASD may be discovered by your doctor during a check-up. If your doctor hears a heart murmur through the stethoscope or finds other signs of a heart defect, he or she may suspect ASD and refer you for tests to determine if it is present.
Those tests may include:
- Echocardiogram, in which sound waves (ultrasound) produce a video image of the heart. An echocardiogram provides your doctor a window into the chambers of your heart to look for defects and allows evaluation of the heart’s pumping strength and examination of its valves.
- Electrocardiogram (ECG or EKG), a test that traces your heart’s rhythm and its electrical activity.
- Chest x-ray, which provides an x-ray image of your heart and lungs.
- Pulse oximetry, which involves placing a small, clip-on device on your finger to measure how much oxygen is in your blood – a possible indication that oxygen-rich red blood is mixing with poorly oxygenated blue blood.
- Angiogram, a test performed in a catheterization laboratory (“cath lab”) in a hospital that helps your doctor assess your heart’s pumping ability, the valves, and blood pressure in the lungs. During an angiogram, a catheter (thin tube) is placed in a vein in your groin or arm and guided to the heart, where images of your heart are then taken using x-ray contrast dye.
Progression and Possible Complications
If a large ASD is not repaired, the amount of blood flowing to the right side of the heart and lungs will increase. Increased blood flow to the lungs causes them to become congested. Congestion of the lungs interferes with their task of transferring oxygen from the air to the blood and transferring carbon dioxide from the blood to the air. Consequently, the lungs have to work harder to do their job. This causes shortness of breath, especially during exertion.
If a moderate or large ASD is not treated, it can lead to:
- Irreversible damage to the blood vessels of the lungs from long-term exposure to abnormally high blood pressure in the lungs (pulmonary hypertension). If allowed to progress, the damage will result in early death (typically in the fourth or fifth decade of life.)
- Possible stroke, which can occur if a blood clot passes to the left side of the heart which otherwise would be filtered out by the lungs.
- Abnormal heart rhythm (too fast and/or an irregular heartbeat) due to stretching of the wall of the right atrium because of enlargement, caused by increased blood flow through it.
Many small- to moderate-sized ASDs can close on their own over time. However, if an ASD has not closed by 5 years of age, most likely it will not close by itself. In this case, closure of the ASD by catheter-based devices or open-heart surgery may be necessary.
Closing the ASD with a Closure Device
Closing the ASD with an implanted closure device is a treatment that helps avoid open-heart surgery. Performed in the hospital’s cardiac catheterization laboratory (or “cath lab”), the procedure involves threading a small, thin tube called a catheter through a vein into the heart, then delivering the closure device through the catheter to the ASD, and closing the opening. Patients who undergo this procedure typically may go home the same day or soon thereafter.
Surgical Closure of the ASD
Open-heart surgery may be recommended if the ASD is too large for treatment with a catheter-based device. During surgery, the surgeon opens the heart and closes the defect by using a patch or sutures. The length of stay in the hospital after this surgery may be from three to five days.
If the ASD does not close on its own, the cardiologist may recommend anti-congestive heart failure medications. These medications do not treat the ASD itself and do not directly make the hole smaller, but they may help control symptoms resulting from the defect.
Anti-congestive heart failure medications include:
- Diuretics: These types of medicines act to cause you to pass more urine, resulting in a smaller blood volume – and a smaller burden on the heart to pump. The most commonly prescribed diuretics are furosemide (Lasix) and thiazides (Diuril and Hydrodiuril). Another commonly used diuretic is spiranolactone (Aldactone). It has a weak diuretic effect and is mainly used because it helps the kidneys retain potassium. Other diuretics tend to waste potassium excessively.
- Inotropes: These medications, which include digoxin, help the heart pump more efficiently (stronger while using less energy).
- Anticoagulants, such as warfarin and aspirin: Anticoagulants thin the blood and help reduce the risk of blood clots, which can cause stroke.
- Afterload-reducing agents: These medicines, which include captopril, are infrequently used in the treatment of ASD. However, when used, they act to reduce the resistance of blood flow to the body. This may lead to less blood crossing the ASD – and improvement in symptoms.
Following closure of an ASD, whether with surgery or with a closure device, patients need to follow-up with their cardiologist on a regular basis. The exact frequency of follow-up depends on several issues unique to each patient. In general, however, these patients will need follow-up of some sort for the rest of their lives, usually yearly early on and then every three to five years.
Consult with your cardiologist about safe levels of exercise or physical activity. Many people with ASD face no restrictions. However, for patients with complications resulting from ASD – heart failure or high blood pressure in the lungs, for example – a doctor may advise some restrictions.