Special Article
Three-Dimensional Imaging and Dynamic Modeling of Systolic Anterior Motion of the Mitral Valve

https://doi.org/10.1016/j.echo.2020.08.019Get rights and content

Highlights

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    3D dynamic modeling can provide incremental value for visualization of SAM.

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    3D SAM imaging novel findings: double-orifice LVOT, dolphin smile, and SAM width.

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    3D TEE imaging is critical for surgical and percutaneous SAM therapies.

Left ventricular outflow tract (LVOT) obstruction in hypertrophic cardiomyopathy (HCM) is often caused by systolic anterior motion (SAM) of the mitral valve caused by the interplay between increased left ventricular (LV) wall thickness and an abnormal mitral valve anatomy and geometry. Three-dimensional (3D) echocardiographic imaging of the mitral valve has revolutionized the practice of cardiology, paving the way for new methods to see and treat valvular heart disease. Here we present the novel and incremental value of 3D transesophageal echocardiography (TEE) of SAM visualization. This review first provides step-by-step instructions on acquiring and optimizing 3D TEE imaging of SAM. It then describes the unique and novel findings using standard 3D TEE rendering as well as dynamic mitral valve modeling of SAM from 3D data sets, which can provide a more detailed visualization of SAM features. The findings include double-orifice LVOT caused by the residual leaflet, the dolphin smile phenomenon, and delineation of SAM width. Finally, the review discusses the essential role of 3D TEE imaging for preprocedural assessment and intraprocedural guidance of surgical and novel percutaneous treatments of SAM.

Section snippets

3D TEE Image Acquisition of SAM

Three-dimensional echocardiographic imaging of SAM is best obtained using 3D TEE rather than transthoracic echocardiography due to the posterior position of the MV and subvalvular apparatus adjacent to the esophagus.

3D Visualization of SAM Width

Three-dimensional TEE imaging easily demonstrates that there is a variation in the extent or width for which the MV protrudes into the LVOT in systole, which is not easily seen by other imaging techniques. In some patients, only a narrow portion of the MV obstructs the LVOT; in others the width is greater. Narrow SAM occupies less space in the outflow tract and for any given LVOT area would be expected to cause less obstruction and lower instantaneous LVOT gradients. This provides a unique

Unique Overall Views

Using these models, one may view SAM from an en face view or from a side/oblique perspective throughout the cardiac cycle (Figure 6, Supplemental Video 6, available at www.onlinejase.com).

3D SAM Width: Implications for Percutaneous SAM Repair

Surgical repair of SAM with septal myectomy is the mainstay for treatment of obstructive HCM and has been performed for >50 years. In recent years the development of HCM centers of excellence have allowed a concentration of surgical expertise and experience, such that in-hospital mortality for myectomy at such centers averages 0.6%. Myectomy can be combined with native MV modifying techniques, such as horizontal anterior mitral leaflet plication, residual leaflet excision (also called ReLex),

Conclusion

Three-dimensional imaging of the MV enables an entirely new method of visualization of SAM. Data sets obtained by 3D TEE can be used to generate unique models of MV anatomy and pathophysiology in obstructive HCM. This novel perspective of 3D TEE visualization has implications not only for elucidation of pathologic mechanisms but also for applications in surgical and percutaneous therapy.

References (18)

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    In particular, the mid-esophageal and transgastric long axis views can provide detailed assessment of the mitral valve apparatus. Three-dimensional technology has been successfully applied in imaging of SAM and associated abnormalities during TTE and TEE examinations (Video 2).115 Because of the close anatomic proximity, it can be hard to distinguish high-velocity LVOT flow from that of MR, which is usually present in patients with SAM.

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A.V. is a consultant for Micro Interventional Devices. M.S. is a member of the Philips, Boston Scientific, and Medtronic speakers' bureaus and a member of Siemens advisory board.

Luigi P. Badano, MD, PhD, FASE, served as guest editor for this report.

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2020 Published by Elsevier Inc. on behalf of the American Society of Echocardiography.