Health Encyclopedia

Atrial septal defect

Definition

Atrial septal defect is an abnormality of the upper chambers of the heart (atria) where the wall between the right and left atria does not close completely. This defect is present at birth (congenital).

Alternative Names

ASD

Causes, incidence, and risk factors

Atrial septal defect (ASD) is a congenital heart defect. 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. Sometimes, blood flows from the right atrium to the left atrium (a right to left shunt).

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:

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

Symptoms

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

Note: People with small-to-moderate-sized defects may show no symptoms, or not until middle age or later.

Signs and tests

Rarely, there may be a palpable pulsation of the pulmonary artery in the chest. Examination with a stethoscope (auscultation) of the heart usually reveals abnormal heart sounds. There may be a murmur caused by the increased blood flow across the pulmonic valve, and the second heart sound is widely split and fixed. Signs of heart failure can occur in adults.

If the shunt is large, increased blood flow across the tricuspid valve (between the right atrium and ventricle) may be responsible for an additional murmur when the heart relaxes between beats.

Tests that may be performed in the diagnosis of ASD include:

Chest x-ray
Echocardiography (ultrasound of the heart)
Doppler study of the heart
Transesophageal echocardiography (TEE)
Cardiac catheterization
Coronary angiography (for patients over 35 years old)
MRI of heart
ECG - may show atrial fibrillation in adults, right atrial and ventricular enlargement, or a pattern of delayed electrical conduction in the heart.

Treatment

ASD may not require treatment if there are few or no symptoms, or if the defect is small. Surgical closure of the defect is recommended if the atrial septal defect is large, the heart is enlarged, or symptoms occur.

A relatively new procedure has been developed to close the defect without surgery. The procedure involves the introduction of an ASD closure device (such as the Amplatzer device) into the heart through catheters. A tiny incision is made in the groin to introduce the catheters. They are then advanced into the heart, where the closure devise is placed across the ASD and the defect is closed.

All atrial septal defect patients may not be eligible for this procedure. Prophylactic (preventive) antibiotics should be given prior to dental procedures to reduce the risk of developing infective endocarditis immediately after surgery for the ASD, but they are not required later on.

Expectations (prognosis)

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.

Complications

Pulmonary hypertension
Arrhythmias, particularly atrial fibrillation
Heart failure

Calling your health care provider

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

Prevention

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

References

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. http://www.mdconsult.com/about/book/83821525-2/instruct.html?DOCID=1549. Accessed December 11, 2007.

Review Date:12/11/2007
Reviewed By:David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.; and Mark A Fogel, MD, FACC, FAAP, Associate Professor of Pediatrics and Radiology, Director of Cardiac MR, The Children's Hospital of Philadelphia.

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