What Is Atrial Septal Defect?

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What Is Atrial Septal Defect?

An Atrial Septal Defect (ASD) is a hole in the part of the septum that separates the atria (the upper chambers of the heart). This hole allows oxygen-rich blood from the left atrium to flow into the right atrium instead of flowing into the left ventricle as it should.

This means that oxygen-rich blood gets pumped back to the lungs, where it has just been, instead of going to the body.

An ASD can be small or large. Small ASDs allow only a little blood to flow from one atrium to the other. Small ASDs don't affect the way the heart works and don't need any special treatment. Many small ASDs close on their own as the heart grows during childhood.

Medium to large ASDs allow more blood to leak from one atrium to the other, and they are less likely to close on their own. Most children who have ASDs have no symptoms, even if they have large ASDs.

The three major types of ASDs are:

• Secundum- This defect is in the middle of the atrial septum. It's the most common form of ASD. About 8 out of every 10 babies born with ASDs have secundum defects. At least half of all secundum ASDs close on their own. However, this is less likely if the defect is large.
• Primum- This defect is in the lower part of the atrial septum. It often occurs along with problems in the heart valves that connect the upper and lower heart chambers. Primum defects aren't very common, and they don't close on their own.

• Sinus Venosus- This defect is in the upper part of the atrial septum, near where a large vein (the superior vena cava) brings oxygen-poor blood from the upper body to the right atrium. Sinus venosus defects are rare, and they don't close on their own.

What are the complications of Atrial Septal Defect?

Over time, if an ASD isn't repaired, the extra blood flow to the right side of the heart and lungs may cause heart problems. Usually, most of these problems don't show up until adulthood, often around age 30 or later. Complications are rare in infants and children.

Possible complications include:

• Right heart failure- An ASD causes the right side of the heart to work harder because it has to pump extra blood to the lungs. Over time, the heart may become tired from this extra work and not pump well.
• Arrhythmias (ah-RITH-me-ahs)- Extra blood flowing into the right atrium through an ASD can cause the atrium to stretch and enlarge. Over time, this can lead to arrhythmias (irregular heartbeats). Arrhythmia symptoms may include palpitations or a rapid heartbeat.
• Stroke- Usually, the lungs filter out small blood clots that can form on the right side of the heart. Sometimes a blood clot can pass from the right atrium to the left atrium through an ASD and be pumped out to the body. This type of clot can travel to an artery in the brain, block blood flow, and cause a stroke.
• Pulmonary hypertension (PH)- PH is increased pressure in the pulmonary arteries. These arteries carry blood from your heart to your lungs to pick up oxygen. Over time, PH can damage the arteries and small blood vessels in the lungs. They become thick and stiff, making it harder for blood to flow through them.

These problems develop over many years and don't occur in children. They also are rare in adults because most ASDs either close on their own or are repaired in early childhood.

Source: Information provided courtesy of the National Heart, Lung, and Blood Institute (NHLBI), a division of the National Institutes of Health (NIH).

National Heart, Lung, and Blood Institute (NHLBI) health-related material is provided for information purposes only and does not necessarily represent endorsement by or an official position of the National Heart, Lung, and Blood Institute or any other Federal agency. Advice on the treatment or care of an individual patient should be obtained through consultation with a physician who has examined that patient or is familiar with that patient's medical history.

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