Artial Septal Defect (ASD)


What is an atrial septal defect?

The normal heart has two sides, which are separated by a muscular wall called the septum. Each side of the heart also has two parts – the upper chamber called an atrium, and the lower chamber called a ventricle.

An atrial septal defect (ASD) is an opening in the wall (the atrial septum)
between the heart’s two upper chambers (the right and left atria). An ASD is one of the defects referred to as “a hole in the heart.”

Normally, the right side of the heart carries deoxygenated blood back into the heart and the left side carries oxygenated blood back out to the body.

An ASD allows the oxygenated blood to pass from the left atrium, through the opening in the septum, into the right atrium causing the two to mix. This leads to increased blood flow through the right side of the heart and lungs. Over time, this “extra” blood volume stresses the heart and causes the right atrium, ventricle and pulmonary arteries to dilate (become wider). This can eventually lead to heart failure, pulmonary hypertension, or heart rhythm abnormalities.

What are the symptoms of atrial septal defect?

Unless the hole is large, an ASD often won’t cause symptoms in infants until they are over 1 year of age. Symptoms of atrial septal defect may include:

  • Heart murmur – the heart sounds abnormal when a doctor listens with a stethoscope
  • Fatigue
  • Racing heartbeat

Atrial septal defects occur in 6 to 8 percent of all children born with congenital heart disease. For unknown reasons, girls have atrial septal defects twice as often as boys.