Regarding “Three-Dimensional Imaging and Dynamic Modeling of Systolic Anterior Motion of the Mitral Valve”

Abstract

We read with great interest the article by Vainrib et al.,1Vainrib A. Massera D. Sherrid M.V. Swistel D.G. Bamira D. Ibrahim H. et al.Three-dimensional imaging and dynamic modeling of systolic anterior motion of the mitral valve.J Am Soc Echocardiogr. 2021; 34: 89-96Abstract Full Text Full Text PDF PubMed Scopus (4) Google Scholar who discuss the role of three-dimensional (3D) transesophageal echocardiography (TEE) imaging in the visualization of systolic anterior motion (SAM) of the anterior mitral valve leaflet (AMVL) in patients with hypertrophic cardiomyopathy (HCM). In this review article the authors give a detailed description of both the utilization and step-by-step approach for 3D TEE imaging of SAM in patients with HCM. We agree with the authors' assertion that 3D imaging provides a unique insight and incremental understanding of SAM and would like to share our experience of using 3D imaging of SAM in the operating room in patients undergoing mitral valve (MV) repair surgery. Similar to Vainrib et al., we use 3D TEE to assess SAM; however, we quantify the degree of SAM as a percentage of left ventricular outflow tract (LVOT) obstruction in order to enhance clinical decision-making. Dynamic LVOT obstruction due to SAM of the AMVL is a well-known complication occasionally seen in the operating room in patients undergoing MV repair surgery.2Maslow A.D. Regan M.M. Haering J.M. Johnson R.G. Levine R.A. Echocardiographic predictors of left ventricular outflow tract obstruction and systolic anterior motion of the mitral valve after mitral valve reconstruction for myxomatous valve disease.J Am Coll Cardiol. 1999; 34: 2096-2104Crossref PubMed Scopus (197) Google Scholar While it is often utilized in the diagnosis of SAM, two-dimensional (2D) imaging does not allow for a global assessment of the LVOT obstruction. Given that the LVOT is a 3D tubular structure and tomographic in nature, 2D imaging provides only cross-sectional information of the imaging plane. Therefore, what may appear to be total occlusion of the LVOT on 2D imaging could possibly only be a partial obstruction. Recognizing the limitation of 2D imaging, it is our routine clinical practice to utilize 3D TEE when SAM and LVOT obstruction are encountered in the operating room.3Cummisford K.M. Manning W. Karthik S. Mahmood F. 3D TEE and systolic anterior motion in hypertrophic cardiomyopathy.JACC Cardiovasc Imaging. 2010; 3: 1083-1084Crossref PubMed Scopus (12) Google Scholar In using 3D TEE, we aim to determine the exact extent of LVOT obstruction to make objective decisions regarding whether surgical intervention is required or not. This is done by using multiplanar reconstruction of the 3D data set to determine the percentage of LVOT obstruction. By using multiplanar reconstruction to obtain the area of the LVOT and then tracing the areas of each orifice of the double-outlet LVOT as created by the portion of the AMVL causing the SAM, we can determine the exact percentage of LVOT obstruction. Using this method, we are able to provide details on the residual orifice space and determine whether the obstruction is of significance or not. While not based on specific studies, it is our clinical experience that as long as there is at least 70% of residual LVOT orifice area available, then there is no significant obstruction or need for surgical intervention. We have utilized this method to confidently ignore the 2D TEE evidence of SAM and avoid a further run of cardiopulmonary bypass and surgical intervention.4Jiang L. Shakil O. Montealegre-Gallegos M. Jainandunsing J.S. Matyal R. Wang A. et al.Systolic anterior motion of the mitral valve and three-dimensional echocardiography.J Cardiothorac Vasc Anesth. 2015; 29: 149-150Abstract Full Text Full Text PDF PubMed Scopus (10) Google Scholar Since its introduction, 3D TEE has become the gold standard for the assessment of many cardiac pathologies, and this also holds true for the assessment of SAM. As demonstrated by Vainrib et al., 3D imaging of SAM in patients with HCM can give insight into the pathogenic mechanism of SAM and also guide surgical and percutaneous interventions. Echocardiographers should also consider the use of 3D TEE when SAM is encountered in the operating room during MV repair surgery as its use can guide treatment and aid in surgical decision-making. Possible future studies using 3D TEE visualization of SAM may be undertaken to evaluate exactly what percentage of LVOT obstruction correlates with elevated LVOT gradients, which would be useful for determining interventions for patients with SAM.