An atrial septal defect (ASD) is a hole in the heart between the upper chambers (atria). The hole increases the amount of blood that flows through the lungs. The condition is present at birth (congenital heart defect).

Small atrial septal defects might be found by chance and never cause a concern. Others close during infancy or early childhood.

A large, long-term atrial septal defect can damage the heart and lungs. Surgery may be needed to repair an atrial septal defect and to prevent complications.


Types of atrial septal defects include:

  • Secundum. This is the most common type of ASD. It occurs in the middle of the wall between the upper heart chambers (atrial septum).
  • Primum. This type of ASD affects the lower part of the atrial septum and might occur with other congenital heart defects.
  • Sinus venosus. This rare type of ASD usually occurs in the upper part of the wall separating the heart chambers. It's also associated with other heart structure changes present at birth.
  • Coronary sinus. In this rare type of ASD, part of the wall between the coronary sinus — which is part of the vein system of the heart — and the left upper heart chamber (left atrium) is missing.


Many babies born with atrial septal defects have no signs or symptoms. Signs or symptoms can begin in adulthood.

Atrial septal defect signs and symptoms can include:

  • Shortness of breath, especially when exercising
  • Fatigue
  • Swelling of legs, feet or belly (abdomen)
  • Irregular heartbeats (arrhythmias)
  • Sensation of a rapid, pounding heartbeat (palpitations) or skipped beats
  • Whooshing sound that can be heard through a stethoscope (heart murmur)

When to see a doctor

Serious congenital heart defects, including large atrial septal defects, are often diagnosed before or soon after a child is born.

Contact your health care provider if you or your child has:

  • Shortness of breath
  • Easy tiring, especially after activity
  • Swelling of legs, feet or belly (abdomen)
  • Sensations of a rapid, pounding heartbeat (palpitations) or skipped beats


The cause of atrial septal defect is unclear. Atrial septal defect is a structure problem that occurs during heart development while a baby is still in the womb.

Genetics, certain medical conditions, use of certain medications, and environmental or lifestyle factors, such as smoking or alcohol misuse, may play a role.

How the heart works

To understand the cause of atrial septal defect, it may be helpful to know how the heart typically works.

The typical heart is made of four chambers — two upper chambers (atria) and two lower chambers (ventricles).

The right side of the heart moves blood to the lungs. In the lungs, blood picks up oxygen and then returns it to the heart's left side. The left side of the heart then pumps the blood through the body's main artery (aorta) and out to the rest of the body.

A large atrial septal defect can cause extra blood to overfill the lungs and overwork the right side of the heart. If not treated, the right side of the heart eventually grows larger and becomes weak. The blood pressure in the arteries in the lungs can also increase, leading to pulmonary hypertension.

Risk factors

Atrial septal defect (ASD) occurs as the baby's heart is developing during pregnancy. Certain health conditions or drug use during pregnancy may increase a baby's risk of atrial septal defect or other congenital heart defect. These things include:

  • German measles (rubella) infection during the first few months of pregnancy
  • Diabetes
  • Lupus
  • Alcohol or tobacco use
  • Illegal drug use, such as cocaine
  • Use of certain medications, including some anti-seizure medications and drugs to treat mood disorders

Some types of congenital heart defects occur in families (inherited). If you have or someone in your family has congenital heart disease, including ASD, screening by a genetic counselor can help determine the risk of certain heart defects in future children.


A small atrial septal defect might never cause any concern. Small atrial septal defects often close during infancy.

Larger atrial septal defects can cause serious complications, including:

  • Right-sided heart failure
  • Irregular heartbeats (arrhythmias)
  • Stroke
  • Early death
  • High blood pressure in the lung arteries (pulmonary hypertension)

Pulmonary hypertension can cause permanent lung damage. This complication, called Eisenmenger syndrome, usually develops over many years and occurs uncommonly in people with large atrial septal defects.

Treatment can prevent or help manage many of these complications.

Atrial septal defect and pregnancy

If you have an atrial septal defect and are pregnant or thinking about becoming pregnant, it's important to talk to your health care provider and to seek proper prenatal care. A health care provider may recommend ASD repair before conceiving. A large atrial septal defect or its complications can lead to a high-risk pregnancy.


Because the cause of atrial septal defect (ASD) is unclear, prevention may not be possible. But getting good prenatal care is important. If you have an ASD and are planning to become pregnant, schedule a visit with your health care provider. This visit should include:

  • Discussing current health conditions and medications. You'll need to monitor certain health conditions, such as diabetes or lupus, during pregnancy. Your health care provider might also recommend adjusting or stopping certain medications before pregnancy.
  • Reviewing your family medical history. If you have a family history of congenital heart defects or other genetic conditions, consider talking with a genetic counselor to determine your specific risks.
  • Getting tested for immunity to German measles (rubella). Rubella in the mother has been linked to some types of congenital heart defects in the baby. If you're not immune, ask your health care provider about getting vaccinated.

Atrial septal defect (ASD) care at Mayo Clinic

March 01, 2022
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