Clinical & Experimental Cardiology
Open Access

Expanding the Role of TAVR to Subaortic Membrane and LVOT Obstruction: A Commentary

Salem Assiri^{* *}Correspondence: Salem Assiri, King Fahad Armed Forces Hospital, Ministry of Defense Health Services, Jeddah, Saudi Arabia, Email:

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Description

Subaortic Membrane (SAM) is a fibromuscular ridge or tunnel located just below the aortic valve that causes fixed subvalvular obstruction. Though frequently congenital, SAM can present or progress later in life, and often coexists with other valvular abnormalities, particularly Aortic Stenosis (AS). Standard treatment includes surgical resection of the membrane, with or without Surgical Aortic Valve Replacement (SAVR), depending on valve morphology and severity [1].

Despite generally good surgical outcomes, certain populations—particularly elderly or comorbid patients—are deemed inoperable or high-risk for open-heart surgery. In such cases, Transcatheter Aortic Valve Replacement (TAVR) has emerged as a less invasive alternative. However, its utility in the context of Subaortic Stenosis (SAS) remains investigational. Because TAVR targets valvular pathology and leaves the subaortic membrane untouched or cover it partially, the hemodynamic outcomes can be variable and depend heavily on the individual anatomy and membrane characteristics and the distance between the membrane and the aortic valve [2].

Clinical indications for TAVR in SAM

 • Concurrent aortic stenosis: Patients with coexistent AS and SAS who are not surgical candidates may benefit from TAVR as a means of relieving the dominant valvular gradient or covering both aortic valve and sub-aortic membrane if feasible.

• Palliative strategy: For patients with significant symptoms and no other options, TAVR can serve as a palliative measure, especially if SAM is non-dominant, relatively thin or close to the aortic valve [3].

• Bridging therapy: In certain cases, TAVR may be used to stabilize the patient, potentially allowing for delayed surgical resection of the membrane when the patient's condition improves.

Procedural and anatomic considerations

Pre-procedural planning is essential. Multimodal imaging—including echocardiography (Transthoracic and trans-esophageal) and contrast-enhanced CT—helps assess the distance between the sub-aortic membrane and the aortic annulus, membrane thickness, associated calcifications and LVOT geometry. A narrow LVOT or prominent thick SAM may prevent proper valve deployment or affect anchoring and expansion [4].

Device choice is also crucial. Balloon-expandable valves, with greater radial force, may perform better in rigid LVOTs, whereas self-expanding valves may reduce trauma in anatomically sensitive areas. Persistent LVOT gradient and paravalvular leak post-TAVR are known risks. Post-deployment imaging is recommended to assess residual gradients and paravalvular leak particularly if the valve will be in low-seated deployment [5].

Current evidence and limitations

Literature on TAVR in patients with SAS is limited to case reports and small series. Outcomes vary based on the anatomical characteristics of the membrane and valve disease severity. Some reports demonstrate favorable symptom relief and gradient reduction, while others note continued symptoms or residual obstruction. To add to it, the long-term durability post- TAVR is not well documented. Given this variability, the use of TAVR in SAS must be approached cautiously and ideally within a research or registry framework or as a last resort [6].

Conclusion

TAVR is not currently a standard treatment for isolated Subaortic Stenosis (SAS) but it may serve as a valuable alternative in select inoperable and high-risk patients, especially those with coexisting aortic stenosis. Procedural success depends heavily on patient selection, imaging, and careful planning. Future investigations should focus on long-term outcomes and the development of adjunctive trans-catheter techniques for direct Subaortic Membrane (SAM) modification or resection. Until then, TAVR in Subaortic stenosis remains an evolving and cautiously off-label promising intervention.

References

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