Functional and Biomechanical Effects of the Edge-to-Edge Repair in the Setting of Mitral Regurgitation: Consolidated Knowledge and Novel Tools to Gain Insight into Its Percutaneous Implementation

Abstract

Mitral regurgitation is the most prevalent heart valve disease in the western population. When severe, it requires surgical treatment, repair being the preferred option. The edgetoedge repair technique treats mitral regurgitation by suturing the leaflets together and creating a doubleorifice valve. Due to its relative simplicity and versatility, it has become progressively more widespread. Recently, its percutaneous version has become feasible, and has raised interest thanks to the positive results of the Mitraclip device. Edgetoedge features and evolution have stimulated debate and multidisciplinary research by both clinicians and engineers. After providing an overview of representative studies in the field, here we propose a novel computational approach to the most recent percutaneous evolution of the edgetoedge technique. Imagebased structural finite element models of three mitral valves affected by posterior prolapse were derived from cinecardiac magnetic resonance imaging. The models accounted for the patientspecific 3D geometry of the valve, including leaflet compound curvature pattern, patientspecific motion of annulus and papillary muscles, and hyperelastic and anisotropic mechanical properties of tissues. The biomechanics of the three valves throughout the entire cardiac cycle was simulated before and after Mitraclip implantation, assessing the biomechanical impact of the procedure. For all three simulated MVs, Mitraclip implantation significantly improved systolic leaflets coaptation, without inducing major alterations in systolic peak stresses. Diastolic orifice area was decreased, by up to 58.9%, and leaflets diastolic stresses became comparable, although lower, to systolic ones. Despite established knowledge on the edgetoedge surgical repair, latest technological advances make its percutanoues implementation a challenging field of research. The modeling approach herein proposed may be expanded to analyze clinical scenarios that are currently critical for Mitraclip implantation, helping the search for possible solutions.

Dynamic and quantitative evaluation of degenerative mitral valve disease: a dedicated framework based on cardiac magnetic resonance imaging

“…On each cMRI image, point coordinates for P i (P i,x , P i,y , P i,z ) are computed using the specific pixel dimension of the image (i.e., 1.25× 1.25 mm), stored in the "Pixel spacing" DICOM field. Subsequently, the geometry of MV annulus is automatically reconstructed through a two-step validated procedure (32,33): (I) a cylindrical reference frame is set with the origin in the center of mass of the MV annular extracted cloud of points, and the z-axis normal to the least-square plane of the annular points; (II) in this local reference frame, the radial (ρ) and axial (h) positions of the points belonging to the annular profile ( Figure S1B, red…”

“…The procedure of CMR segmentation has already been exploited in previous works of the group for the numerical modeling of the MV patient-specific anatomy in order to deepen the mechanisms underlying MV prolapse and investigate the effects of different MV surgical repair techniques (18)(19)(20) or percutaneous approaches (21,22). Briefly, as reported in Figure 1B for a single frame of the R-R interval, two points (in red color) were manually selected on MV annulus in each of the acquired plane; the papillary muscles (PAPs), where visible, were added through a variable number of points (green points), selecting single points or defining a region of interest (ROI), i.e., selecting all the pixels inside it.…”

“…The 3D coordinates of the points selected on each CMR cut-plane were reconstructed from the position of the latter with respect to the CMR rotation axis. At this purpose, Subsequently, the geometry of MV annulus was automatically reconstructed ( Figure 1C) through a two-step validated procedure (22). First, a cylindrical reference frame was set with the origin in the centroid (O) of the extracted cloud of annular points, and the z-axis normal to the leastsquare plane of the annular points defined.…”

Numerical modeling of transapical mitral valve repair

“…Moreover, the simulation of models described by solid elements involves a relatively high computational cost compared to shell elements. Up to 12 hours can be needed to simulate function of the detailed MV model discretized by solid elements (Toma et al 2017), whereas for the model described by shell elements, depending on the mesh size, about half of this time (Sturla et al 2015a), and usually even less (Pappalardo et al 2017), is required.…”

Three-dimensional (3D) printing and its applications for aortic diseases

“…Pre-processing, usually performed by a visualization software, extracts anatomical information from the combination of image slices (14). Moreover, by segmenting, or creating thresholds in the image based upon density, users can create volumes of interest and selectively reconstruct specific anatomical structures or display them in different colors when printed (16).…”