Treatment of Interatrial Septal Aneurysm with Predominant Bowing to the Right
For patients with asymptomatic interatrial septal aneurysm (ASA) with predominant bowing to the right, no antithrombotic therapy is recommended unless there are additional risk factors present. 1, 2
Classification and Clinical Significance
Interatrial septal aneurysm is defined as a congenital malformation of the atrial septum characterized by bulging of the septum overlying the fossa ovalis region, with an excursion of >10 mm beyond the plane of the atrial septum. The prevalence is estimated at 2-3% of the adult population 2.
Based on the direction of bulging, ASA can be classified as:
- Type 1R: Bulging to the right atrium only
- Type 2L: Bulging to the left atrium only
- Type 3RL: Major excursion to the right atrium, lesser to the left
- Type 4LR: Major excursion to the left atrium, lesser to the right
- Type 5: Bidirectional and equidistant movement 3
Treatment Algorithm Based on Clinical Presentation
1. Asymptomatic ASA with Right-Sided Bowing
- No antithrombotic therapy is recommended 1, 2
- Regular cardiac follow-up to monitor for development of associated conditions
2. ASA with Patent Foramen Ovale (PFO)
- For patients aged 18-60 years with cryptogenic stroke: Consider PFO closure plus long-term antiplatelet therapy over antiplatelet therapy alone 1, 2
- For patients >60 years with cryptogenic stroke: Antiplatelet therapy alone is recommended 2
- For patients with cryptogenic stroke and PFO who experience recurrent events despite aspirin therapy: Consider vitamin K antagonist therapy (target INR 2.5; range 2.0-3.0) and evaluation for device closure 1
3. ASA with History of Cryptogenic Stroke (without PFO)
- Initial therapy: Aspirin (50-100 mg/day) 1, 2
- For recurrent events despite aspirin: Consider vitamin K antagonist therapy (target INR 2.5; range 2.0-3.0) 1, 2
4. ASA with Evidence of Deep Vein Thrombosis (DVT) and Cryptogenic Stroke
- Recommend vitamin K antagonist therapy for 3 months (target INR 2.5; range 2.0-3.0) 1
- Consider device closure evaluation 1
Special Considerations
Risk stratification: The risk of stroke is significantly higher when ASA is associated with PFO, with odds ratios of 15.59 for patients <55 years and 5.09 for patients >55 years 2.
Monitoring: For patients on antiplatelet or anticoagulant therapy, standard monitoring for medication efficacy and adverse effects is essential 2.
Surgical intervention: While rare, surgical correction may be considered in cases with recurrent embolic events despite medical therapy. The procedure involves excising the aneurysmal part of the interatrial septum and replacing it with a pericardial patch 4.
Mechanism of embolism: Three potential mechanisms link ASA to embolic events:
- Thrombus formation in or around the ASA
- Paradoxical embolization through an interatrial communication
- Associated mitral valve prolapse 5
Pitfalls and Caveats
Incidental finding vs. clinical significance: Many ASAs are discovered incidentally. Careful evaluation for associated conditions (PFO, atrial septal defect, mitral valve prolapse) should be performed before attributing symptoms to the ASA itself 5.
Age considerations: The benefit of interventional approaches like PFO closure appears to be limited to younger patients (typically <60 years) 1.
Diagnostic accuracy: Transesophageal echocardiography is superior to transthoracic echocardiography for diagnosing ASA and associated conditions 6, 5.
Evidence limitations: Most recommendations for isolated ASA management are based on expert consensus rather than randomized controlled trials, as the condition is relatively uncommon and often asymptomatic 6.
By following this algorithm and considering these special factors, clinicians can provide appropriate management for patients with interatrial septal aneurysm with predominant bowing to the right, focusing on preventing thromboembolic complications while avoiding unnecessary interventions in low-risk patients.