Design parameters and physiologic factors governing mitral valve annular loading following device implantation

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Pierce, Eric L.
Yoganathan, Ajit P.
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The range of implantable devices to correct mitral regurgitation (MR) is diverse and continually expanding. It consists mainly of annuloplasty rings, which restore native valve competency, and prosthetic valve replacements. Both attach to the mitral annulus via suture anchoring. Additionally, many transcatheter mitral valve (TMV) replacements, in which anchoring and sealing often rely on radial expansion against the mitral annulus, are now developing rapidly. The mechanical interactions of all such devices with the annulus remain poorly studied, yet are critical for device safety and performance. In this work, custom measurement techniques were applied to study device-annulus interactions in clinically and industrially relevant in vivo, ex vivo, and in vitro models. First, the impacts of mitral annuloplasty ring shape, size, and stiffness on suture dehiscence likelihood were assessed across 37 ovine subjects and a series of benchtop tests. A critical role of ring flexibility was uncovered, which suggested a promising new design concept to improve suture retention without compromising effectiveness. Second, TMV radial expansion forces and paravalvular leakage dynamics were quantified in explanted porcine hearts, as functions of the device’s profile. Findings quantitatively demonstrated key advantages of a non-circular TMV shape, implications of annular oversizing, and criteria for industrial TMV test system performance. Taken together, these studies yield significant new insights into best practices for MR device design, assessment, and usage.
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