An atrial septal defect is a congenital heart issue. According to the Centers for Disease Control and Prevention (CDC), it develops in about 1 in 1,859 babies in the United States.

An atrial septal defect is a hole in the wall inside the heart known as the septum, which divides the left and right atrium. According to 2018 research, this condition is the third most common type of heart irregularity seen in newborns.

Small holes often repair themselves. But doctors usually recommend surgically closing medium or large defects even if they aren’t causing symptoms. This can help prevent problems or complications later in life.

To understand what an atrial septal defect is, it helps to know how the heart works.

an illustration of an unaffected heart vs a heart with an atrial septal defectShare on Pinterest
Illustration by Sophia Smith

Your heart is made up of four chambers. The top two chambers are your left and right atrium and the bottom chambers are your left and right ventricle. Blood moves through these chambers in a set order:

  1. Oxygen-poor blood flows from your body into your right atrium.
  2. It then flows from your right atrium into your right ventricle, which pumps it to your lungs.
  3. Oxygen-rich blood then returns from your lungs into your left atrium.
  4. It flows from your left atrium to your left ventricle, which pumps it to the rest of your body.

This article will take a closer look at the different types of atrial septal defects, how they’re diagnosed and treated, and what the outlook is for this type of heart condition.

Doctors divide atrial septal defects into four primary categories, depending on where the hole is:

  • Ostium secundum defect. This is when the hole develops in the middle part of your septum. This is the most common type. According to a 2015 review, it makes up about 75 percent of cases.
  • Ostium primum defect. In this instance, the hole develops in the lower part of your septum. This type of atrial septal defect makes up about 15 to 20 percent of cases.
  • Sinus venosus defect. With this type, the hole develops in the upper part of your septum. A 2019 case study suggests sinus venosus has a lower rate of spontaneous closure than other types.
  • Coronary sinus defect. This is when the hole develops in the wall that separates your left atrium from your coronary sinus. Coronary sinus defects are the rarest type.

An atrial septal defect is a congenital defect, meaning that it’s present from birth. According to the CDC, the cause of most atrial septal defects isn’t known.

Every baby is born with an opening between the upper chambers of the heart. This hole keeps blood away from the lungs while a baby is in the womb. The opening is no longer needed once a baby is born and closes within several weeks to months, according to the American Heart Association (AHA). If the hole is larger than usual it may not close after birth.

Mutations in genes may play a role in the development of some heart defects. A combination of genetic factors and exposure to certain chemicals in the womb may also contribute to these changes.

Ostium primum defects commonly occur in people with Down syndrome or Ellis-van Creveld syndrome.

The symptoms of an atrial septal defect are often mild and usually aren’t noticeable in infancy. The CDC says some babies with severe defects may have symptoms such as:

  • frequent infections
  • fatigue when feeding
  • stroke

The most common sign in childhood, and often the only sign, is a heart murmur. Children with severe defects, particularly with ostium primum defects, may experience symptoms such as:

A 2011 study found that up to 33.8 percent of adults with unrepaired atrial septal defects have heart palpations.

Early diagnosis and screening is important and usually leads to favorable outcomes, according to 2020 research. Older studies have found that 90 percent of people with untreated large atrial septal defects don’t live to their 60th birthdays.

An atrial septal defect is often not diagnosed until late childhood or adulthood. Small defects might not cause any noticeable symptoms.

Atrial septal defects are most often diagnosed when a doctor listens to your heart through a stethoscope and detects a murmur.

If a doctor hears a murmur, they may order a special ultrasound of your heart called an echocardiogram. This type of diagnostic test uses sound waves to produce live images of your heart. This allows your doctor to see the inside of your heart, how well it’s working, and how blood is flowing through it.

Another diagnostic tool your doctor may order is a transesophageal echocardiogram. With this procedure, a thin probe will be passed down your throat into your esophagus, which is close to the upper chambers of your heart. The probe will then use high frequency sound waves to produce detailed images of the structures inside your heart.

The seriousness of an atrial septal defect depends on:

  • the size of the hole
  • how much blood is going across
  • which direction the blood is moving in

The left side of your heart usually pumps blood to your body, while the right side pumps blood to your lungs. A hole between your atria can cause oxygenated blood to flow back into the right side of your heart.

This buildup of blood can increase the pressure in the blood vessels that supply your lungs. Over many years, this pressure can damage your heart and lungs.

Small holes less than 5 millimeters (about 0.2 inches) can heal by themselves within 1 year after birth. Defects over 1 centimeter (about 0.4 inches) are most likely to require treatment to avoid complications later in life.

About half of septal defects resolve by themselves without treatment, according to 2017 research. The other half require treatment either with a procedure called cardiac catheterization and percutaneous closure or with open heart surgery.

Watchful waiting

When an atrial septal defect is diagnosed in a young child, doctors often recommend watchful waiting to see if the hole will close on its own. The doctor may prescribe medications to treat symptoms during this time.

Cardiac catheterization

Doctors can use a procedure called cardiac catheterization to treat heart defects without opening your chest. During this procedure, your cardiologist inserts a thin, flexible tube through a blood vessel in your leg or neck. Then, they thread it to your heart and deploy a closure device to plug the hole.

This procedure has a lower risk of complications than open heart surgery but can only be used for ostium secundum defects.

Open heart surgery

Open heart surgery is usually performed early in childhood. Surgery may be needed if the hole is large or is not an ostium secundum defect.

The AHA says small unrepaired holes rarely cause problems later in life. They typically don’t require you to limit physical activity or change your lifestyle.

People with larger defects are more likely to need treatment. Your cardiologist may recommend some lifestyle changes until you can get treatment, and while you are recovering from your treatment.

You can usually return to your usual activities once you’re fully recovered and have had a post-treatment checkup with your doctor. Once the hole is closed, follow-up surgery is rarely needed, and you can live an active life.

An atrial septal defect is one of the most common congenital heart irregularities. It occurs when there’s a hole between the upper two chambers in the heart. If the hole is small, it can heal by itself. Larger holes may need treatment to prevent complications later in life.

Many people don’t know they have an atrial septal defect until late childhood or adulthood. If you receive an atrial septal defect diagnosis, your doctor can provide more information about the type of defect it is and the treatment that’s right for you.