P31. Cardiac CT in the Pre-Procedural Planning for Transcatheter Mitral Valve Replacement

E.M. Holper, D. Gopal, R.L. Smith, A. Avila, E. Figueroa, M. Lovil, S. Basra, W. Faircloth, P.A. Grayburn, D.L. Brown, M.J. Mack, A. Gopal
The Heart Hospital Baylor, Plano, TX, USA

Objectives: To propose a simple method of post-processing 4-Dimensional Cardiac CT for the pre-procedural screening, planning and follow up imaging for Transcatheter Mitral Valve Replacement (TMVR) in the setting of mitral annular calcification (MAC). 
Methods: We retrospectively reviewed Cardiac Computed Tomographic Angiography (CT) imaging performed prior to mitral valve surgery in patients with MAC at a single center. A contrast based 4D-CT was performed on a GE 256-Revolution CT scanner (GE Healthcare, Waukesha, WI, USA), and the images were then transferred to an advanced workstation capable of image post-processing and manipulation. Using multiphase analysis, the best systolic and diastolic phases were selected, and used for further post-processing (figure). Initially using multi-planar reformats, the mitral annulus plane was defined and aligned. Using enhanced 3D rendering to better characterize MAC, images were generated with short axis and long axis views to portray suitability of the MAC distribution for TMVR. Mitral annulus was sized next (perimeter, area and average diameter). Septal-mitral annulus distance and septal thickness were obtained to gauge the LVOT clearance that should be accommodated to plan for septal debulking to make space for the left ventricular presence of the deployed TMVR. All patient underwent port access mitral valve replacement with a SAPIEN 3 Transcatheter Heart Valve (Edwards Lifesciences, Irvine, CA). 
Results: From 9/2015 through 10/2016; seven patients underwent 4D CT imaging prior to the above mitral valve surgery for MAC. The mean age was 79.1 years and 100% were women. 3 patients were undergoing mitral valve surgery for mitral stenosis and 4 for combined mitral stenosis and regurgitation. Utilizing the pre-procedural planning information, patients successfully underwent the procedure. The mitral annulus sizing helped in selecting the valve size and correlated with balloon sizing during procedure. The septal-mitral annulus distance, septal thickness, and valve size mannequin embeds were very useful in planning septal debulking to make room for the left ventricular presence of the deployed TMVR, and helped avoid LVOT obstruction following the procedure. During follow up, 4DCT imaging was obtained to verify the valve stability in relationship to the septal region, and for verifying valve leaflet function (figure). Even though the TMVR may appear protruding into the LVOT, because of the stent frame with open cells, no significant LVOT obstruction was noted. 
Conclusions: TMVR in the presence of MAC is performed by a variety of approaches, and pre-procedural Cardiac Computed Tomographic Angiography (CT) planning is crucial for the success of the TMVR procedure. CT is extremely useful in screening and selecting patients for this procedure, and for valve sizing and deployment planning.