What Is Atrial Septal Aneurysm?

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The atrial septum is a membrane that separates the upper left and upper right chambers of the heart, called the atria. If the septum weakens or bulges, as can occur because of a heart defect, it can push into these spaces. This is known as an atrial septal aneurysm (ASA).

An ASA keeps the heart from working properly and from pumping blood that returns to the right atria to pick up oxygen back out to the body. The condition is one possible cause of stroke, a potentially life-threatening blockage of blood flowing to the brain.

This article looks at how an ASA is linked to having a stroke, as well as its connection to other health issues. It also discusses how this type of aneurysm may be treated.

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Atrial Septal Aneurysm Symptoms

Symptoms of an atrial septal aneurysm are similar to those seen in other congenital heart defects, such as shortness of breath or fatigue.

However, there may be no symptoms at all.


An atrial septal aneurysm increases the risk of stroke or a transient ischemic attack (TIA), a so-called "mini" or "warning" stroke.

It is particularly linked to cryptogenic strokes, or those without a known cause, which are also associated with genetic heart conditions like mitral valve prolapse and abnormal heart rhythms like atrial fibrillation. Up to 40% of strokes have no known origin.

Stroke symptoms are different from those of ASA and include:

  • Facial drooping
  • Speech changes
  • Difficulty moving or walking
  • Vision changes
  • Change in mental status
  • Headaches

These are signs that immediate medical help is needed.


A developing fetus has a hole in the heart wall that usually closes at birth when it starts breathing on its own. When the hole never closes the way it should, it's called a patent foramen ovale (PFO). ASA is often linked to this heart defect.

PFO happens in about 25% of the population. Most cases don't cause any serious problems. Still, the hole in the heart wall allows blood to pass between the chambers, and an already weakened septum can develop an aneurysm.

ASA is far more rare than PFO, but it's linked to the heart defect in at least 60% of cases.

A September 2021 review looked at 12 studies to evaluate these kinds of atrial septal abnormalities and to better understand the link between atrial issues and cryptogenic stroke.

The risk of stroke was higher in people with ASA, as well as those with atrial fibrillation heart rhythms. But the study wasn't definitive, with the authors noting only that these atrial weaknesses may cause stroke.


Imaging is key to an ASA diagnosis. An ASA appears as an unusually large and bulging membrane that moves between the two atria.

In many cases, a complete echocardiogram of the heart may be done if a person has a related congenital heart condition.

It also may be done if someone has a stroke and doctors are trying to find out why. They may look for blood clots in the left atrium, a PFO, a mitral valve prolapse, or the ASA.

A person's overall health and family history also are needed for a complete diagnosis. That's especially true if there is a personal history of strokes, TIAs, or other cardiovascular issues.


It may seem obvious to just surgically close a PFO because there's such a strong link between the defect and an ASA. But many people live with a PFO without issue, and doctors continue to disagree about the benefits of such a procedure.

Medication is another treatment approach. If a doctor thinks a person with an ASA is at high risk for stroke, or if one has already occurred, they may want to try drugs that prevent blood clots and other strategies that will limit stroke risk.


For many people, an ASA may happen because they already had an underlying condition at birth. They may not even know that they have an ASA for a long time or possibly ever. But it does increase the chance of having a stroke, so it's important to know the signs and symptoms.

If you have concerns about a congenital heart problem and its risks, let your doctor know.

A Word From Verywell

Some cases of congenital heart conditions persist without affecting people much. This may be so much so that people come to consider them "minor" heart issues—or forget about them entirely.

It's important, however, that your doctor know about them. Aside from the risk of ASA, these defects can cause other concerns as well.

If you're not sure if your heart defect is part of your medical record, ask your healthcare provider.

6 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Razaq M, Parihar RK, Saini G. Atrial septal aneurysm and stroke. Ann Pediatr Cardiol. 2012;5(1):98-9. doi:10.4103/0974-2069.93726

  2. Yaghi S, Elkind MS. Cryptogenic stroke: A diagnostic challenge. Neurology: Clinical Practice. 2014;4(5):386-393. doi:10.1212/cpj.0000000000000086

  3. Centers for Disease Control and Prevention. Stroke Signs and Symptoms. Reviewed August 28, 2020.

  4. Ioannidis SG, Mitsias PD. Patent foramen ovale in cryptogenic ischemic stroke: direct cause, risk factor, or incidental finding? Front Neurol. 2020;0. doi: 10.3389/fneur.2020.00567

  5. Sun H, Zhou C, Xu L, Xu T. A meta-analysis of the association of atrial septal abnormalities and atrial vulnerabilityMedicine. 2021;100(35):e27165. doi: 10.1097/md.0000000000027165

  6. Menardi AC, Ribeiro PJ, Evora PR. Atrial septal aneurysm and atrial septal defect association – an uncommon but well-recognized association. Brazilian Journal of Cardiovascular Surgery. 2021. doi:10.21470/1678-9741-2020-0464

Additional Reading

By Jose Vega MD, PhD
Jose Vega MD, PhD, is a board-certified neurologist and published researcher specializing in stroke.