Atrial septal aneurysm means that there is a bulge in the interatrial septum. It may not present with symptoms. However, it can occur alongside other heart problems that cause symptoms such as irregular heartbeat, difficulty breathing, and fatigue.

The interatrial septum is a wall of tissue that separates the left and right atria of the heart. A doctor may uncover an interatrial septal aneurysm, which cardiologists also call an atrial septal aneurysm (ASA), while looking for something else. Many people live normal lives with this condition, especially if the aneurysm is small.

However, it has links with patent foramen ovale, which can increase the risk of stroke and arterial embolisms. Embolisms occur when something, often a blood clot, gets into the bloodstream and blocks an artery. ASA may also occur alongside other heart abnormalities.

It can occur in children and adults, and doctors consider it a congenital anomaly.

This article will explain what an ASA is, its symptoms, causes, and treatment.

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The heart’s two upper chambers, known as the atria, pump blood into the ventricles. The atrial septum is a thin layer of tissue that divides them, preventing blood from flowing between the two atria.

The right atrium receives deoxygenated blood, while the left receives oxygenated blood. The septal wall stops the blood from mixing.

A bulge in the atrial septum is an ASA. This can be a defect a baby is born with, or it can develop over time. Sometimes weakness in the septum causes it to bulge. In some cases, an ASA may be a sign of underlying heart disease.

Doctors define ASA as a movement in the septum of 10 millimeters (mm) to either the right or left or a total combined movement of 15 mm.


Researchers classify ASA on the basis of its location and severity:

  • Type 1R: The bulge enters only the right atrium.
  • Type 2L: The bulge enters only the left atrium.
  • Type 3R: The biggest part of the bulge goes into the right atrium, and the smaller part of the bulge enters the left atrium.
  • Type 4RL: The reverse of type 3RL, which means that a major part of the aneurysm is in the left atrium, with the smaller portion in the right atrium.
  • Type 5: The bulge extends equally into both atria.

An ASA can be asymptomatic. A doctor may discover it as part of a routine screening or when looking for something else.

However, ASA can occur alongside other heart defects. When this happens, a person may have other heart or breathing symptoms, such as:

  • irregular or rapid heart rate
  • trouble breathing, especially with mild exertion such as climbing stairs
  • low energy
  • fatigue
  • other types of cardiovascular health issues

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ASA can be an incidental finding that a doctor discovers while evaluating unrelated symptoms. Doctors believe it to be a congenital condition, meaning it is present at birth. However, it may have an association with the following conditions:

  • Valve disease: Many different conditions can damage the valves of the heart, including rheumatic heart disease, endocarditis — which is an infection of the heart — heart failure, high blood pressure, and heart attack.
  • Patent foramen ovale: This is a hole in the heart that is present at birth. The heart normally has a hole during fetal development. When it does not close, it causes patent foramen ovale.
  • Other heart conditions: ASA sometimes occurs with other heart conditions, including congenital heart defects and those that damage the heart over time.

Treatment depends on whether an ASA causes symptoms. Treatment options include:

  • Addressing underlying heart disease: This may involve lifestyle changes, blood pressure medication, cholesterol medication, and other management techniques.
  • Closing a patent foramen ovale: This can reduce the risk of stroke and embolism.
  • Blood thinners: These may lower the risk of stroke and embolisms.

When ASA is an isolated occurrence and does not cause symptoms, and when it is not the result of an underlying disease, it may not require treatment. A doctor may want to continue to monitor the condition, however.

There is little research on treatment options and an ongoing debate among doctors about whether and when to treat this condition. However, in a person with a history of stroke or heart disease, treatment is usually necessary.

Doctors diagnose ASA by using an echocardiogram. This test visualizes the heart’s chambers and allows doctors to measure the deviation of the atrial septum. This helps to confirm the presence of ASA, as well as associated findings such as patent foramen ovale.

Read more about heart tests here.

The outlook for ASA depends on why a person has the condition and their overall health. ASA is congenital but has associations with other heart conditions such as mitral valve disease, patent foramen ovale, and tricuspid valve disease.

The outlook may depend on how big the ASA is. Smaller ASAs have a good outlook, while larger ones related to patent foramen ovale increase a person’s risk of stroke and embolism.

Read more about how to improve heart health here.

Diagnosis of a heart defect can be very worrying for a person. ASA may be a relatively benign incidental finding or accompany an underlying heart health issue.

It is important that people with ASA discuss with their doctor the potential causes of their condition and treatment options. Everyone can benefit from exercise, a healthy diet, and other heart health interventions, so people with ASA should implement these lifestyle changes.