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Atrial septal defect (ASD) is a congenital heart defect in which the wall that separates the upper heart chambers (atria) does not close completely. Congenital means the defect is present at birth.

ASD

In fetal circulation, there is normally an opening between the two atria (the upper chambers of the heart) to allow blood to bypass the lungs. This opening usually closes around the time the baby is born.

If the ASD is persistent, blood continues to flow from the left to the right atria. This is called a shunt. If too much blood moves to the right side of the heart, pressures in the lungs build up. The shunt can be reversed so that blood flows from right to left. Many problems can occur if the shunt is large, but small atrial septal defects often cause very few problems and may be found much later in life.

ASD is not very common. When the person has no other congenital defect, symptoms may be absent, particularly in children. Symptoms may begin any time after birth through childhood. Individuals with ASD are at an increased risk for developing a number of complications including:

• Atrial fibrillation (in adults)
• Heart failure
• Pulmonary overcirculation
• Pulmonary hypertension
• Stroke

Small-to-moderate-sized defects may produce no symptoms, or not until middle age or later. Symptoms that may occur can include:

• Difficulty breathing (dyspnea)
• Frequent respiratory infections in children
• Sensation of feeling the heart beat (palpitations) in adults
• Shortness of breath with activity

The doctor may heart abnormal heart sounds when listening to the chest with a stethoscope. A murmur may be heard only in certain body positions, and sometimes a murmur may not be heard at all. The physical exam may also reveal signs of heart failure in some adults.

If the shunt is large, increased blood flow across the tricuspid valve may create an additional murmur when the heart relaxes between beats.

Tests that may done include:

• Cardiac catheterization
• Chest x-ray
• Coronary angiography (for patients over 35 years old)
• Doppler study of the heart
• ECG
• Echocardiography
• Heart MRI
• Transesophageal echocardiography (TEE)

With a small-to-moderate atrial septal defect, a person may live a normal life span without symptoms. Larger defects may cause disability by middle age because of increased blood flow and shunting of blood back into the pulmonary circulation.

• Arrhythmias, particularly atrial fibrillation
• Heart failure
• Pulmonary hypertension
• Stroke

Call your health care provider if symptoms indicating an atrial septal defect develop.

There is no known way to prevent the defect, but some of the complications can be prevented with early detection.

Webb GD, Smallhorn JF, Therrien J, et al. Congenital heart disease. Zipes DP, Libby P, Bonow RO, Braunwald E, eds. Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine. 8th ed. St. Louis, Mo: WB Saunders; 2007: chap 61.