Biomechanical engineering comparison of four leaflet repair techniques for mitral regurgitation using a novel 3-dimensional-printed left heart simulator

Abstract

Objective: Mitral valve repair is the gold standard treatment for degenerative mitral regurgitation; however, a multitude of repair techniques exist with little quantitative data comparing these approaches. Using a novel ex vivo model, we sought to evaluate biomechanical differences between repair techniques.

Methods: Using porcine mitral valves mounted within a custom 3-dimensional-printed left heart simulator, we induced mitral regurgitation using an isolated P2 prolapse model by cutting primary chordae. Next, we repaired the valves in series using the edge-to-edge technique, neochordoplasty, nonresectional remodeling, and classic leaflet resection. Hemodynamic data and chordae forces were measured and analyzed using an incomplete counterbalanced repeated measures design with the healthy pre-prolapse valve as a control.

Results: With the exception of the edge-to-edge technique, all repair methods effectively corrected mitral regurgitation, returning regurgitant fraction to baseline levels (baseline 11.9% ± 3.7%, edge-to-edge 22.5% ± 6.9%, nonresectional remodeling 12.3% ± 3.0%, neochordal 13.4% ± 4.8%, resection 14.7% ± 5.5%, P < 0.01). Forces on the primary chordae were minimized using the neochordal and nonresectional techniques whereas the edge-to-edge and resectional techniques resulted in significantly elevated primary forces. Secondary chordae forces also followed this pattern, with edge-to-edge repair generating significantly higher secondary forces and leaflet resection trending higher than the nonresectional and neochord repairs.

Conclusions: Although multiple methods of degenerative mitral valve repair are used clinically, their biomechanical properties vary significantly. Nonresectional techniques, including leaflet remodeling and neochordal techniques, appear to result in lower chordal forces in this ex vivo technical engineering model.

Keywords: 3D, 3-dimensional; FBG, Fiber Bragg Grating; MR, mitral regurgitation; biomechanics; chordae forces; ex vivo model; leaflet remodeling; leaflet resection; mitral valve repair; neochord.

Biomechanical comparison of various mitral valve repair techniques.

Figure 1

A, Schematic of the Stanford left heart simulator in the mitral testing configuration with each component labeled. B, Close-up view of FBG force sensor attached to a chordae tendinea of interest. PL, Posterior leaflet; AL, anterior leaflet; TEE, transesophageal echo; APM, anterolateral papillary muscle; FBG, fiber Bragg Gratings; PPM, posteromedial papillary muscle.

Video 1

En face view of high speed videometric footage highlighting each repair technique. Video available at: https://www.jtcvs.org/article/S2666-2507(21)00671-4/fulltext.

Figure 2

En face view of each valve at baseline, after induction of prolapse, and after each repair technique during mid-systole demonstrating leaflet coaptation differences among each technique.

Figure 3

A, Regurgitant fraction is significantly higher in the edge-to-edge (E) group relative to the other repair techniques when normalized to baseline values (P < .01 for each). B, Primary chordae forces relative to baseline are significantly higher in the edge-to-edge technique versus the neochord technique (P = .002). The resection technique also results in higher primary chordae forces when compared with the neochord (P = .001) and nonrsectional remodeling (P = .04) techniques. C, Secondary chordae forces relative to baseline forces were significantly elevated after edge-to-edge repair versus neochord repair (P = .03) and nonresectional remodeling techniques (P = .02), whereas the other repair techniques resulted in similar secondary chordae forces compared with baseline levels. NC, Neochord; NR, nonresectional remodeling; R, resection. The P values refer to post hoc comparisons with Bonferroni correction from the mixed model.