Mitral Valve Chordae Tendineae: Topological and Geometrical Characterization

Abstract

Mitral valve (MV) closure depends upon the proper function of each component of the valve apparatus, which includes the annulus, leaflets, and chordae tendineae (CT). Geometry plays a major role in MV mechanics and thus highly impacts the accuracy of computational models simulating MV function and repair. While the physiological geometry of the leaflets and annulus have been previously investigated, little effort has been made to quantitatively and objectively describe CT geometry. The CT constitute a fibrous tendon-like structure projecting from the papillary muscles (PMs) to the leaflets, thereby evenly distributing the loads placed on the MV during closure. Because CT play a major role in determining the shape and stress state of the MV as a whole, their geometry must be well characterized. In the present work, a novel and comprehensive investigation of MV CT geometry was performed to more fully quantify CT anatomy. In vitro micro-tomography 3D images of ovine MVs were acquired, segmented, then analyzed using a curve-skeleton transform. The resulting data was used to construct B-spline geometric representations of the CT structures, enriched with a continuous field of cross-sectional area (CSA) data. Next, Reeb graph models were developed to analyze overall topological patterns, along with dimensional attributes such as segment lengths, 3D orientations, and CSA. Reeb graph results revealed that the topology of ovine MV CT followed a full binary tree structure. Moreover, individual chords are mostly planar geometries that together form a 3D load-bearing support for the MV leaflets. We further demonstrated that, unlike flow-based branching patterns, while individual CT branches became thinner as they propagated further away from the PM heads towards the leaflets, the total CSA almost doubled. Overall, our findings indicate a certain level of regularity in structure, and suggest that population-based MV CT geometric models can be generated to improve current MV repair procedures.

A noninvasive method for the determination of in vivo mitral valve leaflet strains

“…The present study builds upon over a century of investigations into MV mechanics and owes much to recent achievements in the development of high‐fidelity computational models of the MV . Moreover, the overarching objective of devising noninvasive methods to estimate MV strains in vivo is motivated by an increasingly compelling body of evidence that supports hypotheses of bidirectional causal links between tissue‐level deformations and cell‐mediated growth and remodeling events .…”

“…These concerns have been addressed in detail by several recent investigations into MV geometry characterization and computational modeling of the MV. In our previous studies, we adopted a bottom‐up approach to develop highly detailed models of the MV leaflets and MVCT and then sought to determine the level of fidelity required to perform accurate FE simulations of the MV . We first acquired high‐resolution micro–computed tomography imaging data for a population of ovine MVs .…”

“…This extensive data set was then used to perform a detailed analysis of the chordal and leaflet structures. We showed in a fundamental analysis of the MVCT that chordal geometry follows certain regularities—for example, MVCT branching patterns follow a full binary tree topology . Further, we developed highly detailed curve skeleton models of the MVCT enriched with smooth cross‐sectional area fields.…”

“…Methodologies for in vitro MV imaging, image processing, and FE mesh generation have been described previously in detail . Briefly, three freshly excised ovine MV specimens were sutured to an adjustable annulus holder by a ford interlocking stitch and mounted into an extensively validated cylindrical left heart simulator .…”

The Pursuit of Engineering the Ideal Heart Valve Replacement or Repair: A Special Issue of the Annals of Biomedical Engineering

“…The article by Khalighi et al aims to take advantage of regularities in the mitral valve structure to improve current mitral valve repair strategies. 8 New basic understanding of the limitation in durability as well as poor aortic sinus flow patterns among current TAVR devices is the focus of the articles by Martin and Sun and Midha et al respectively. 9,10 A variety of innovative tissue engineering strategies are being employed for the development of living heart valve replacements.…”