Atrial Septal Aneurysm: Causes, Treatment, and Outlook

Medically Reviewed By Angela Ryan Lee, MD, FACC

An atrial septal aneurysm (ASA) is a bulge in the wall that separates the heart‘s top two chambers. Many ASAs do not cause symptoms but can be linked to complications that cause irregular heart rates and breathing difficulty. Some clinicians consider ASAs to be benign — mild or small ASAs may be manageable with monitoring and treatment to reduce the risk of more serious complications. However, some people may need more treatment.

This article explains ASA, its types, symptoms, and causes. It also discusses when to contact a doctor, the diagnosis, treatment, and outlook.

What is an atrial septal aneurysm?

A clinician listens to someone's heart with a stethoscope.
Photography by Inti St Clair/Getty Images

An ASA is a difference in the structure of the heart.

The heart has four chambers that pump blood and oxygen throughout the body. Two chambers, called the atria Trusted Source PubMed Central Highly respected database from the National Institutes of Health Go to source , pump blood into the chambers, the ventricles.

Between the two atria is a thin layer of tissue, the interatrial septum. The tissue prevents oxygenated blood from mixing with deoxygenated blood. ASA can also be known as an interatrial septal aneurysm.

An ASA is a bulge in the structure of the interatrial septum. Doctors can also define ASA as an area of excessive movement in the interatrial septum, protruding at least 10 millimeters (mm) from the rest of the wall. The American Society of Echocardiography defines an ASA as a movement of at least 15 mm.

Below is an example imaging scan of an ASA.

A medical image showing an imaging scan of an atrial septal aneurysm.

The arrow highlights an ASA protruding from the left atrium (LA) into the right atrium (RA) of the heart.

Purvis JA, Morgan DR, Hughes SM – The Ulster medical journal (2011)

Atrial septal aneurysm symptoms

Some people with an ASA will experience noticeable symptoms. A doctor may notice signs during a checkup.

ASAs commonly occur with other heart conditions. For example, nearly 75% of people with an ASA also have a hole in the septal wall, known as a patent foramen ovale (PFO).

Other conditions linked to ASA include:

  • atrial septal defect, a hole in the septum
  • atrial arrhythmias, irregular heart rhythms
  • arterial embolism, whereby blood clots move from another part of the body and interrupt blood flow, possibly causing stroke
  • valve conditions, such as mitral regurgitation, a leak in a valve known as the mitral valve

Symptoms linked to these related conditions may include:

Learn more about stroke symptoms and when to seek help.

When to see a doctor

Contact your doctor immediately if you experience ASA symptoms or have questions about your heart and breathing. This includes symptoms that are mild or that go away and come back.

Some ASA symptoms are similar to those of other conditions, which can be medical emergencies, such as a heart attack. PFO with ASA may also increase the risk of stroke.

Seek emergency care or call 911 for any of the following symptoms:

Causes of atrial septal aneurysm

Clinicians believe ASA may be a congenital condition, or present since birth. Genetic or structural differences may cause a congenital condition when a fetus grows.

Some researchers say ASA may develop less often throughout life because of conditions that alter the pressure in the atria. Conditions that may affect atrial pressure include:

More research is needed to confirm and understand the factors that may cause ASA.

Diagnosing atrial septal aneurysm

To diagnose ASA, clinicians can use echocardiography, an ultrasound test that shows the heart’s structure. If clinicians notice a bulge in the atrial septum that is bigger than 10–15 mm, they will diagnose it as an ASA.

Your doctor may also do additional testing to rule out other conditions.

After finding an ASA, your medical team may conduct a bubble study to check for a PFO. A bubble study involves injecting agitated saline into a vein while viewing the heart and watching to see whether any microbubbles cross the interatrial septum.

Some people with ASAs do not receive a diagnosis until later in life. This may happen if a diagnosis wasn’t made for a congenital ASA or if you developed an ASA later. In such cases, a doctor may start diagnosis by reviewing your symptoms and medical history and listening to your heart with a stethoscope.  

Treatment for atrial septal aneurysm

Your treatment may depend on the size of the ASA and whether it is causing complications.

Possible treatments may focus on addressing any underlying cause and reducing the risk of complications. Treatments can include:

  • Medication: Blood thinning, cholesterol, and blood pressure medication may help manage underlying heart conditions.
  • Surgery: Procedures may help repair Trusted Source PubMed Central Highly respected database from the National Institutes of Health Go to source the ASA or other structural heart conditions contributing to your heart condition.
  • Lifestyle changes: Changes that may support cardiovascular health and reduce the risk of complications such as stroke include:
    • eating a diet low in saturated and trans fats, sodium, and added sugars
    • following your doctor’s treatment plan
    • maintaining a moderate weight
    • regular physical activity

A cardiologist can determine treatment and interventions to support your health.

Atrial septal aneurysm outlook

Factors that may impact the outlook of ASA include:

  • the size and severity of the ASA
  • the underlying cause
  • whether you experience complications
  • whether you receive effective treatment

Some clinicians consider some ASAs to be benign — they may not cause symptoms or complications. Also, they may be temporary or improve on their own.

Still, because complications are possible, treatment may be needed for some people.

Contact a doctor for advice on treatment and outlook.


An atrial septal aneurysm (ASA) is a bulge in the wall between the heart’s atrial chambers. It may not cause symptoms, but it can appear with other conditions that cause difficulty with breathing, irregular heartbeats, and fatigue.

ASAs can form at birth or develop later. Genetic differences or preexisting cardiovascular conditions can cause ASAs.

Medication, surgery, and lifestyle changes can help treat an ASA and reduce the risk of complications such as stroke.

Seek immediate medical advice for symptoms affecting your heart or breathing.

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Medical Reviewer: Angela Ryan Lee, MD, FACC
Last Review Date: 2023 Jul 28
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