What is an Atrial Septal Defect (ASD)?

What is an Atrial Septal Defect (ASD)?

An atrial septal defect (ASD) is a hole in the wall, or septum, between the heart’s two upper chambers. When this occurs, some oxygen-rich blood that normally gets pumped through the body from the heart’s left upper chamber flows into the right upper chamber instead and then into the lungs. This creates extra stress on the right side of the heart and the lungs. 

Atrial septal defects are present from birth, although patients may not experience symptoms until adulthood. 

Types of Atrial Septal Defect


There are four primary types of atrial septal defect, each characterized by their location in the septum. 

  • Secundum atrial septal defects - the most common diagnosed type of ASD. These defects are found in the middle of the atrial septum.
  • Primum ASDs - form in the lower part of the septum. Patients with this type of ASD often have abnormalities of the heart valves. Primum ASDs sometimes occur with Down Syndrome. 
  • Sinus venosus ASDs - occur in the back of the atrial septum, most often at the top of the wall, but occasionally at the bottom. Individuals with this rare form of ASD also typically have abnormal connections of the veins returning from the lungs (pulmonary veins).  
  • Coronary sinus AS - also referred to as unroofed coronary sinus, is an extremely rare birth defect of the heart wall. Patients with this defect have a defect in the wall between the left atrium and the coronary sinus (a large vein that brings oxygen-poor blood back from the heart muscles).

Signs and Symptoms of Atrial Septal Defects


Signs and symptoms of atrial septal defects vary widely depending on the age of the patient and the size and type of defect present. 

In most children, atrial septal defects do not produce any symptoms. Instead, a healthcare provider may diagnose the problem when they detect an unusual sound listening to the heart with a stethoscope (a heart murmur).  

When atrial septal defect symptoms do occur in children, they are non-specific and most often include:

  • Frequent respiratory infections
  • Delayed growth
  • Poor appetite and low body weight
  • Tiring easily with exercise

Rarely, children with an ASD may also experience:

  • Difficulty breathing
  • Feeling of a pounding heartbeat

Young patients who experience symptoms are more likely to require early treatment.

Adults are far more likely than children to have symptoms related to an atrial septal defect. For that reason, an atrial septal defect is considered the most commonly missed congenital heart defect in children.

Symptoms usually occur by age 40 and may include:

  • Shortness of breath during exercise
  • Tiredness
  • Rapid or pounding heartbeat
  • Swelling in the arms and legs

Individuals who experience these symptoms should seek medical attention from a cardiologist to explore treatment options.

What Causes Atrial Septal Defects?


The causes of atrial septal defect are not well understood.They occur very early in the growing fetus when the developing walls that separate the right side of the heart from the left do not connect properly.In some cases, this abnormality is linked with genetic mutations. 

Other factors that may increase a woman’s risk of giving birth to a child with ASD include:

  • Certain medical conditions and medications
  • Smoking
  • Consuming alcohol

Risk Factors

Risk Factors

A woman’s health and behavior can increase their risk of having a baby with an atrial septal defect. In addition to smoking and alcohol consumption individual factors may include:

  • Lupus 
  • Diabetes
  • Rubella (German Measles)
  • Illegal drug use
  • Some medications used in the treatment of seizures and mood disorders



While some atrial septal defects are quite small and never produce any symptoms, patients with larger defects typically have a subtle onset of complications, including:

  • Exercise intolerance and fatigue. Young adults may begin to notice that they can no longer exert themselves as they could previously.
  • Heart palpitations. A skipping or fluttering of the heartbeat which can sometimes be mistaken for a panic attack.

Infrequently, patients with larger atrial septal defects will have more severe complications, including:

  • Swelling of the legs. If the right side of the heart is working too hard, the blood can back up in the veins, and water can leak out of the blood vessels, particularly in the feet and ankles.
  • Blueness of the lips and fingernails. If the blood pressure in the lungs is too high (pulmonary hypertension) from years of excessive blood flow to the lungs through the atrial septal defect, the blood flowing across the defect can reverse directions. This allows the low-oxygen blood from the right side of the heart to cross to the left side and dilute the normally high oxygen levels on that side.
  • Atrial fibrillation. A heart rhythm problem associated with atrial septal defect in older adults. These patients can have persistent, rapid heart rates, light-headedness, fainting and shortness of breath.
  • Stroke. Blood clots that normally occur in the right side of the heart can cross the defect to the left side and be pumped to the brain.

Pregnancy with an Atrial Septal Defect

Women diagnosed with an atrial septal defect and wishing to have children need to take special precautions. In nearly all cases, the cardiologist will recommend repairing the defect before the woman becomes pregnant.  

Because repairing an atrial septal defect is safe in most cases, your doctor may recommend repair the defect to avoid any complications. After the repair, pregnancy can proceed normally. Very small ASDs do not significantly affect a pregnancy.   



In some cases, it may not be possible to prevent an ASD. Because ASD occurs in the developing fetus, certain lifestyle factors may impact a woman’s health before and during pregnancy. In order to prevent ASD from developing in expecting mothers and women trying to conceive, it is suggested to avoid: 

  • Alcohol and illegal drugs, especially cocaine
  • Smoking or use of any tobacco products
  • Exposure to second-hand smoke

Other factors may include: 

  • Preexisting medical conditions or any medications you are taking may pose an increased risk of pregnancy complications. Certain medications may need to be changed during pregnancy.
  • Rubella (German measles) vaccination, in advance of pregnancy, if the woman does not have immunity
  • Genetic conditions, such as the mother's congenital heart disease, which may increase risk. A genetic counselor can play an important role in this assessment.
Get Care

Trust NewYork-Presbyterian for Atrial Septal Defect Care

If you are seeking care for yourself or a child with an atrial septal defect, schedule an appointment at one of NewYork-Presbyterian’s multiple locations throughout New York City, Westchester or the Hudson Valley.

Our highly experienced cardiologists provide comprehensive evaluation and a full range of available treatment options for atrial septal defect care. Cardiovascular care services at NewYork-Presbyterian cover a full range of cardiac conditions, including congenital heart defects, general cardiology, cardiac surgery, and more.