Predicting LVOT Obstruction in Transcatheter Mitral Valve Implantation: Concept of the Neo-LVOT.

OUTFLOWTRACT OBSTRUCTION IS A FEAREDAND POTENTIALLY LETHAL COMPLICATION OF TRANSCATHETER mitral valve replacement (TMVR), mitral valve-in-valve (ViV), and valve-in-ring (ViR) procedures as well as implantation of transcatheter heart valves in calcific mitral valve disease. These procedures ultimately lead to elongation of the outflow tract into the left ventricle, whereas the pre-existing “native” left ventricular outflow tract (LVOT) confined by the most basal septum and the intervalvular fibrosa remains unchanged (Figure 1). The newly created elongation of the outflow tract is confined posteriorly by the deflected anterior mitral valve leaflet in TMVR (Figures 1 and 2), ViR, and calcific mitral valve procedures or by the deflected bioprosthetic leaflets and transcatheter heart valve struts in ViV procedures. To better discriminate from the native LVOT, we propose to refer to the newly created elongation as the “neo-LVOT” (1). Although risk factors for narrow neo-LVOT dimensions can be both deviceand anatomy-related (Figure 3), we propose to perform a patientspecific assessment by means of computed tomography (CT)-based, virtual, stereolithographic device implantation. This requires segmentation of the native mitral annulus (2), the bioprosthetic sewing ring, or the annuloplasty ring, with subsequent definition of the annular plane and the annular trajectory by means of the least squares plane method to serve as anatomical landmarks for the subsequent device simulation (Figure 4) (1). With integrated device contours, the neo-LVOT can be segmented by means of a centerline technique to finally generate an orthogonal cross-sectional plane for planimetric “neo-LVOT” assessment (Figure 5). Here, we illustrate the concept of the neo-LVOT as well as the simulation and segmentation techniques essential to neo-LVOT prediction using cardiac CT (Figure 6). Transcatheter valve implantation for native mitral valve disease and for failed surgical mitral valve replacement or repair elongate the outflow tract into the left ventricle, referred to as neo-LVOT. Pre-procedural CT-based device simulation may aid in identifying patients at an increased anatomical risk for small neo-LVOT dimensions and ultimately obstruction of the outflow tract.