Atrial Septal Defect

An atrial septal defect (ASD) is a hole in the atrial septum, which is the wall that separates your heart’s two upper chambers (atria). An ASD is a congenital heart defect (something you’re born with) that happens when the septum doesn’t form properly. It’s also called a “hole in the heart.”

An ASD allows an abnormal shunt, meaning an abnormal passageway for blood that shouldn’t be happening. Normally, oxygen-rich blood flows from your left upper chamber (atrium) down to your left lower chamber (ventricle), and then out to supply oxygen to your body. An ASD causes some blood from your left atrium to flow in the wrong direction, into your right atrium. Your right atrium contains oxygen-poor blood that needs to cycle through your lungs. So, your right atrium now has extra blood that ultimately goes to the lungs.

This wrong-way leak might be minor and not cause any problems. In those cases, the ASD can be left alone without treatment. Other times, it can lead to problems with your heart or lungs. The bigger the ASD, the more likely it is to cause symptoms and need treatment.

What are the different types of atrial septal defects?

There are four main types of atrial septal defects. They’re defined by their location in the atrial septum.

• Secundum ASDs are in the middle of your atrial septum. This is the most common type of ASD, (80% of all ASDs).
• Primum ASDs are in the lower part of your atrial septum. Babies with primum ASDs may also have other heart defects. These include endocardial cushion defect, atrioventricular septal defect, tricuspid valve defects and mitral valve defects. Primum ASDs are commonly linked with Down syndrome.
• Sinus venosus ASDs are in the upper or lower back part of your atrial septum. This type is linked with defects in the right pulmonary vein or large veins in the heart called superior or inferior vena cava.
• Unroofed coronary sinus is the rarest type of ASD (less than 1% of all ASDs). It involves a missing or incomplete wall between your coronary sinus (a group of veins connected to your heart) and your left atrium. It’s more often linked with another complex congenital heart disease.

How common are atrial septal defects?

An atrial septal defect is one of the most common types of congenital heart defects in children. It occurs in approximately 1 to 2 out of 1,000 live births. About 1 in 1,859 babies are born with an atrial septal defect in the U.S. This adds up to about 2,118 babies born with ASD each year.

What conditions are associated with atrial septal defects?

Some babies born with an atrial septal defect also have other heart defects or genetic disorders. Some associated heart defects include:

• Mitral valve disease.
• Pulmonary stenosis.
• Ventricular septal defect (VSD).

Associated genetic disorders include:

• Holt-Oram syndrome.
• Down syndrome.
• Thrombocytopenia-absent radii (TAR) syndrome.

What is the difference between an atrial septal defect and a patent foramen ovale?

An atrial septal defect (ASD) and a patent foramen ovale (PFO) are both openings in the atrial septum. But ASD is a congenital heart defect, meaning it’s a problem that occurred while a fetus was still in the uterus. Septal tissue should’ve formed in that part of the atrial septum, but didn’t. So a baby is born with a hole in their heart.

A patent foramen ovale isn’t a congenital heart defect. Tissue isn’t missing from the atrial septum. Instead, a PFO happens when a normal flap-like opening in a baby’s heart (foramen ovale) doesn’t seal shut after birth. The foramen ovale is normal, and we all have one when we’re born. This is a normal pathway to allow oxygen-rich blood from the placenta to circulate to the fetus’ brain while in the uterus.

When we’re born, we no longer need the foramen ovale since our lungs start working. So it usually closes on its own soon after birth and completely seals off in a couple of days or weeks after. When it doesn’t close on its own, it’s called a patent foramen ovale. “Patent” means open or failing to close.

A PFO is usually smaller than an ASD. That’s why it doesn’t usually cause any problems or symptoms. The risk of symptoms and problems goes up when an opening in the septum is bigger.

PFOs are much more common than ASDs. Estimates show that about 1 in 4 adults have a PFO. Most people never know they have this small opening in their hearts. It’s usually harmless, but people who have a PFO along with heart problems such as atrial fibrillation may face a higher risk of a stroke.

How does an atrial septal defect affect a person’s body?

A small ASD doesn’t affect your body much. But larger ASDs can strain the right side of your heart. That’s because the right side of your heart now has extra blood it must pump out to your lungs. Plus, this extra blood flow can slowly damage the blood vessels in your lungs.

Problems with large ASD include:

• Right heart enlargement, which can lead to heart failure if left uncorrected for a very long period of time.
• Abnormal heart rhythm (arrhythmia), including atrial fibrillation or atrial flutter. At least half of adults over age 40 with an ASD have an arrhythmia.
• Stroke.
• Pulmonary hypertension. This is high blood pressure in the arteries that supply blood to your lungs.
• Eisenmenger syndrome. This condition can happen in people who have an ASD along with severe pulmonary hypertension.