Atrial Septal Defect (ASD)

Atrial Septal Defect is an opening, or hole, between the heart's two upper chambers (the right and left atria). The opening is usually found in the mid-portion of the interatrial septum, or dividing wall between the two upper chambers of the heart.

The atrial septum helps separate the unoxygenated blood in the right atrium from the oxygen-rich blood in the left atrium. In case of an ASD, some of the oxygen-rich blood in the left atrium will go through the defect and mix with the unoxygenated blood at the right atrium.

Atrial Septal DefectAtrial septal defects occur in about 10% of children born with congenital heart defects. Girls have ASD twice as often as boys.

There are many different types of atrial septal defects. The most common type of ASD is called ostium secundum, an opening of the mid-portion of the interatrial septum. The less common type of atrial septal defects include:

Primum ASD
This type of ASD involves an opening in the lower portion of the interatrial septum. In the simple form it behaves just as any other ASD. However, it is usually associated with other congenital heart defects such as AV Canal and Mitral Regurgitation.
Sinus venosus
This is a rare form of ASD in which the opening is at the uppermost portion of the interatrial septum. It is usually associated with partial anomalous pulmonary venous drainage.
Coronary Sinus ASD
This is a very rare type of ASD involving an opening in the roof of the coronary sinus vein. This type of ASD may be isolated but it may also involve other types of congenital heart defects. Due to the awkward position of this opening it makes the oxygen-rich blood pumped out of the left heart less rich in oxygen.
Other rare types of ASD may be closely associated with the inferior vena cava.


Atrial septal defects occur during fetal life when the partitioning process (during the formation of the heart chambers) does not occur completely, leaving an opening in the interatrial septum.

Rarely, atrial septal defects may run in the family or may be the result of a chromosomal abnormality. Most atrial septal defects occur sporadically (by chance), with no clear reason for their development.


Most children have no symptoms and seem healthy. The mixing of blood through the ASD produces an overload of blood in the right heart. This is usually well tolerated. Some of the atrial septal defects, if small enough, may become smaller with time and even close spontaneously. Patients with small to moderate ASD are usually asymptomatic.

If the ASD is large or moderately large then it will allow a large amount of blood to pass through the opening into the right heart and the right ventricle and lungs will become overworked, and symptoms may be noted. Symptoms may include:

  • Delayed weight gain and poor growth
  • Child tires easily, especially when playing
  • Fatigue
  • Excessive sweating
  • Rapid breathing
  • Poor feeding
  • Shortness of breath
  • Frequent respiratory infections including pneumonia
  • Rarely, symptoms of congestive heart failure

The symptoms of an ASD may resemble other medical conditions. Always consult with your child's physician or Dr. Villafañe for a more definite diagnosis.


The Electrocardiogram may show certain abnormalities like incomplete right bundle branch block and/or right ventricular enlargement. In rare occasions, it may show abnormalities in the electrical conduction system of the heart including abnormal heart rhythm, slow or fast heartbeats. A chest x-ray is usually normal; however, in case of a moderate large ASD, the heart may be enlarged because the right heart has to handle larger amounts of blood than normal. Also, there may be changes that take place in the lungs due to extra blood flow that can be seen in the chest x-ray.

The Echocardiogram is the most useful test to detect an ASD. Some atrial septal defects may produce no murmur, yet they may be picked up by a color-Doppler echo. The echocardiogram will help determine the location and size of the ASD, as well as how much blood is passing through it. Follow-up echocardiograms may be helpful determining if the ASD is getting smaller or, in case of a moderate-large ASD, confirm if there is progressive right heart enlargement.

A cardiac catherization is usually not necessary. A decision making process of whether a child may need closure of an ASD is usually done with non-invasive tests.


Children with small and even small to moderate ASD may not require any interventional treatment or surgery but just clinical follow-up. It is unusually rare for a child to require closure of an ASD during the first few years of life. It depends on how symptomatic or how enlarged the heart may be. The specific treatment for an ASD will be determined by Dr. Villafañe based on several factors, which may include:

  • Your child?s age, symptoms and overall health
  • The size of the ASD and degree of right heart enlargement
  • Response to cardiac medications, if indicated
  • Chances of the ASD getting smaller with time
  • Significant symptoms or abnormal heartbeats associated with the ASD
  • Prognosis
  • Your opinion or preference

Usually a moderate-large ASD will be closed prior to your child starting school. Lung problems may develop from long-term exposure to extra blood volume.

Treatment may include

Cardiac medications
Most children have no symptoms and require no medications at all. However, some children may need to take medications such as a water pill.
cardiac catherization
An ASD may be closed by means of heart surgery or by using a transcatheter device. A secundum ASD may be closed by using a patch-shaped umbrella or discs. This device is inserted through the ASD by using a small flexible tube called a catheter. This method requires a rather small incision at the groin area, avoiding the need for heart surgery.
Heart surgery
Closure of an atrial septal defect is carried out through an incision in the right anterior chest or in the middle of the chest (chest bone). After the chest is opened an incision is performed in the right heart to visualize the ASD. The ASD may be closed with stitches if it is small to moderate. A patch may be used in case of a larger ASD. The right atrium is then closed and the heart is re-started as the heart-lung machine is withdrawn. The hospital stay is just a few days. Closure of an atrial septal defect is considered a very low-risk procedure. Complications may include clot formation, abnormal heartbeats, infection, embolization, pericardial effusion and even cardiac tamponade.


The majority of patients with an ASD will lead a healthy life. Patients with repaired ASD or small to moderate ASD rarely have any problems. About one-third of ASDs may close spontaneously. About one-third of ASDs will get smaller and one-third will require closure. Less than 20% will get larger. Between 12-18% of patients with ASD may develop abnormal heartbeats including slow heartbeats and/or fast heart beat, Atrial Fibrillation, Atrial Flutter, Sick Sinus Syndrome, Sinus Bradycardia and heart block. A small percentage of patients with ASD may end up requiring a cardiac pacemaker.

Long-term complications of patients with ASD are rare but include:

  • Paradoxical emboli in which a clot or air may go through the ASD into the left heart and brain
  • Stroke
  • Congestive heart failure
  • Pulmonary hypertension (high pressure in the lungs)
  • Abnormal heartbeats
  • Complications from deep-sea scuba diving and others.

Our Mission

Children's Heart Specialists, PSC is committed to provide comprehensive pediatric cardiac services to infants, children and young adults. We strive to insure the highest quality in non-invasive cardiovascular testing. Our medical staff is committed to being board certified in pediatric cardiology and adult congenital heart disease.

Our goal is to provide the highest quality of care with compassion and respect to our patients and their families.

Accredited in Echocardiography


We do not give any medical advice or recommendations about you or your child's health in this website. The medical information that appears on this website is to be used as a general guide about heart defects and symptoms. Medical advice is discussed at the time of your consultation with Dr. Villafañe.