The atrial septal defect is a hole in the wall that separates the two upper chambers of the heart. This condition is congenital. The defect allows oxygen-rich blood to leak into the oxygen-poor blood chambers in the heart. Small atrial septal defects may close on their own during infancy or early childhood, but large and long standing ones can cause damage to the lungs and heart. Small defects do not generally cause a problem, but adults who have had undetected atrial septal defect may suffer heart failure or high blood pressure. 


It is common that babies born with atrial septal defects do not have associated symptoms. In adults, however, signs and symptoms tend to begin by the age of 30, or not occur until much later. The symptoms may include:

  • Shortness of breath, especially when exercising,
  • Tiredness,
  • Swelling of legs, feet or abdomen,
  • Heart palpitations or skipped beats,
  • Frequent lung infections,
  • Stroke,
  • Heart murmur, a whooshing sound that can be heard through a stethoscope.


There's often no clear cause of atrial septal defects although medical professionals know that heart defects present at birth (congenital) arise from errors early in the heart's development. Genetics and environmental factors may also play a role.

An atrial septal defect (ASD) allows freshly oxygenated blood to flow from the left upper chamber of the heart (left atrium) into the right upper chamber of the heart (right atrium). There, it mixes with deoxygenated blood and is pumped to the lungs, even though it is already refreshed with oxygen.

Risk Factors

Researchers have not exactly discovered why atrial septal defects occur, but congenital heart defects appear to run in families and sometimes occur with other genetic problems, such as the Down syndrome.

Some conditions during pregnancy may increase the  risk of having a baby with a heart defect, including:

  • Rubella infection.
  • Drug, tobacco or alcohol use, or exposure to certain substances.
  • Diabetes or lupus.
  • Obesity.
  • Phenylketonuria (PKU).


A small atrial septal defect, which often closes during infancy may never cause any problems.

However, larger defects can cause mild to life-threatening problems, including:

  • Heart failure on  the right side
  • Heart rhythm abnormalities (arrhythmias)
  • Increased risk of a stroke

The risk of congenital heart disease is higher for children of parents with congenital heart disease. People with a congenital heart defect, repaired or not, who want to have a child should  discuss it beforehand with a doctor.


In most cases, atrial septal defects cannot be prevented. Planning to become pregnant may require a preconception visit with the doctor.