Atrial Septal Defect (ASD)

Definition:

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

Causes, incidence, and risk factors

An 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 about the time the baby is born. If the ASD is persistent (remains open), blood continues to flow from the left to the right atria. The opening between the chambers is called a shunt.

ASD is present in 4 out of 100,000 people. When the person has no other congenital defect, symptoms may be absent, particularly in children. Symptoms usually have manifested by age 30. Individuals with ASD are at an increased risk for developing a number of complications including the following:

  • infective endocarditis (a bacterial infection of the heart)
  • heart failure
  • atrial fibrillation, which is an abnormally fast heart rhythm.

Symptoms

People with small-to moderate-sized defects may show no symptoms at all, or not until middle age or later. The typical symptoms of an ASD are the following:

  • frequent respiratory infections in children
  • difficulty breathing (dyspnea )
  • shortness of breathe with activity
  • sensation of feeling the heart beat (palpitations )

Signs and tests

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 signs of heart failure. 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.

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

  • A chest X-ray
  • An echocardiography (ultrasound of the heart) or a contrast echocardiography
  • A color Doppler/Echo study of the heart
  • Transesophageal echocardiography (TEE)
  • A cardiac catheterization
  • A coronary angiography (for patients over 35 years old)
  • An MRI of the chest (sometimes)

An ECG may show atrial fibrillation, right atrial 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 or if symptoms occur.

Recently, a new procedure, percutaneous ASD closure, has been developed to close the defect without open heart surgery. This involves the introduction of a closure device into the heart through wires or catheters.

A tiny incision is made in the groin to introduce the catheters. They are then advanced into the heart where the closure device is deployed across the ASD and the defect is closed.

This procedure is relatively new and may not be applicable to all patients. The size of the opening and its location, especially proximity to the valves of the heart, are prime determining factors for this procedure. Prophylactic (preventive) antibiotics should be given prior to dental procedures to reduce the risk of developing infective endocarditis.

Deployment of the Amplatzer Atrial Septal Defect Occluder

Figure 1
Figure 1 – With fluoroscopic and echocardiographic guidance, the cardiologist inserts the device through the hole in the septum. The device is then partially deployed. As it is deployed from the catheter, it expands like a tiny umbrella to a size that will cover the opening in the septum.

Figure 1
Figure 2 – The cardiologist gently pulls the device against the opening. The device is then further deployed from the catheter, creating a second cover for the opening on the other side of the septum.

Figure 1
Figure 3 – Once the cardiologist confirms a snug fit of the occluder against the septal wall, the device is released from the catheter. The deployed occluder seals closed the atrial septal defect.

Images used with permission of the AGA Medical Corporation.

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
  • Infective endocarditis

Prevention

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