The heart is a four-chambered muscular organ divided by internal walls, called septa, which separate oxygen-rich from oxygen-poor blood. The atrial septum divides the two upper chambers, the right and left atria. When a doctor mentions the atrial septum is aneurysmal, they are referring to a specific, observable change in the shape and movement of this dividing wall. This finding is a structural description, not necessarily a disease, but it prompts a closer examination of the heart’s function and potential associations.
Defining Atrial Septal Aneurysm
An atrial septal aneurysm (ASA) is a localized, mobile, and redundant bulging of the interatrial septum, the wall separating the upper heart chambers. The term “aneurysmal” describes an excessive, floppy, pouch-like movement of this septal tissue, typically involving the fossa ovalis. This variation in heart structure is present from birth.
To be classified as aneurysmal, the septal tissue must exhibit significant movement during the cardiac cycle. Criteria for an ASA include a protrusion of the septum of at least 10 millimeters (mm) beyond the atrial wall into either the right or left atrium, or a combined total excursion of 15 mm into both chambers. This abnormal mobility causes the septum to oscillate back and forth between the two atria in response to pressure changes during the heartbeat. ASA is frequently associated with other structural variations, such as a Patent Foramen Ovale (PFO), which is a small, unclosed flap in the septal wall.
Identifying the Condition Through Diagnostic Imaging
The presence of an atrial septal aneurysm is primarily identified using echocardiography, which employs sound waves to create moving images of the heart. The initial screening tool is Transthoracic Echocardiography (TTE), where the probe is placed on the chest wall. TTE visualizes the abnormal motion of the atrial septum and provides an initial clue about the aneurysm’s size and mobility.
TTE has limitations in clearly defining the full anatomy and can miss an ASA in many cases. For definitive confirmation, detailed measurement, and better visualization of associated defects, Transesophageal Echocardiography (TEE) is often required. TEE is considered the gold standard because it involves passing a specialized probe down the esophagus, placing it directly behind the heart to provide superior, high-resolution images of the atrial septum.
During the echocardiogram, especially with TEE, a contrast study using agitated saline (a “bubble study”) may be performed to assess for interatrial shunting. This study helps determine if blood, and potentially a blood clot, can cross the septal wall from the right side of the heart to the left, which is a crucial detail for understanding the clinical significance of the finding.
Clinical Significance and Associated Health Risks
The clinical relevance of an atrial septal aneurysm is primarily related to its association with thromboembolic events, which are blockages caused by blood clots. An ASA is found more frequently in patients who have experienced a cryptogenic stroke. While an isolated ASA may be benign, the risk becomes more pronounced when combined with a Patent Foramen Ovale (PFO).
The combination of an ASA and a PFO creates a mechanism for paradoxical embolism. A blood clot originating in the veins, such as a deep vein thrombosis, travels to the right side of the heart. Instead of going to the lungs, the clot can pass through the PFO, especially when right atrial pressure is momentarily higher (e.g., during a cough). Once the clot crosses the septum into the left side of the heart, it can travel to the brain, causing an ischemic stroke or a Transient Ischemic Attack (TIA).
The redundant, mobile nature of the aneurysmal septum may also increase the risk of clot formation directly on the tissue, though paradoxical embolism remains the primary concern. Studies indicate that the presence of both an ASA and a PFO significantly increases the risk of recurrent stroke, prompting physicians to look closely for an associated PFO as the ASA acts as a marker for elevated embolic risk.
Monitoring and Management Strategies
The management approach for an atrial septal aneurysm depends heavily on whether the patient has experienced a stroke or TIA and if the ASA is associated with a PFO or other septal defect. For asymptomatic patients with an ASA as an incidental finding, the primary strategy is surveillance. This involves regular clinical follow-up and repeat echocardiography, typically every one to two years, to monitor for changes or complications.
In patients who have suffered an embolic event, the focus shifts to preventing future strokes. Medical management often involves antiplatelet therapy, such as aspirin, or anticoagulation medication (blood thinners) like warfarin or direct oral anticoagulants. Antiplatelet agents prevent platelets from sticking together, while anticoagulants inhibit the clotting process.
For younger patients (under 60 years old) who have experienced a cryptogenic stroke and have both an ASA and a PFO, guidelines often favor percutaneous closure. This catheter-based procedure deploys a small device to permanently close the PFO, eliminating the path for paradoxical emboli to reach the brain. Closure is typically considered when the risk of recurrent stroke is deemed high, usually due to the presence of both the PFO and the aneurysmal septum.