Large Animal Translational Validation of 3 Mitral Valve Repair Operations for Mitral Regurgitation Using a Mitral Valve Prolapse Model: A Comprehensive In Vivo Biomechanical Engineering Analysis
Authors: Zhu Yuanjia , Yajima Shin , Park Matthew H. , Venkatesh Akshay , Stark Charles J. , Tran Nicholas A. , Walsh Sabrina K. , Ethiraj Sidarth , Wilkerson Robert J. , Lin Luca E. , Lee Seung Hyun , Gates Kate Y. , Arthur Justin D. , Baker Sam W. , Mullis Danielle M. , Wu Catherine A. , Harima Shun , Pokhrel Bipul , Resuello Dominique , Bergamasco Hunter , Wu Matthew A. , Baccouche Basil M. , Pandya Pearly K. , Elde Stefan , Wang Hanjay , Woo Y. Joseph 
Published: April 2024

BACKGROUND:
Various mitral repair techniques have been described. Though these repair techniques can be highly effective when performed correctly in suitable patients, limited quantitative biomechanical data are available. Validation and thorough biomechanical evaluation of these repair techniques from translational large animal in vivo studies in a standardized, translatable fashion are lacking. We sought to evaluate and validate biomechanical differences among different mitral repair techniques and further optimize repair operations using a large animal mitral valve prolapse model.

METHODS:
Male Dorset sheep (n=20) had P2 chordae severed to create the mitral valve prolapse model. Fiber Bragg grating force sensors were implanted to measure chordal forces. Ten sheep underwent 3 randomized, paired mitral valve repair operations: neochord repair, nonresectional leaflet remodeling, and triangular resection. The other 10 sheep underwent neochord repair with 2, 4, and 6 neochordae. Data were collected at baseline, mitral valve prolapse, and after each repair.

RESULTS:

All mitral repair techniques successfully eliminated regurgitation. Compared with mitral valve prolapse (0.54±0.18 N), repair using neochord (0.37±0.20 N;
P
=0.02) and remodeling techniques (0.30±0.15 N;
P
=0.001) reduced secondary chordae peak force. Neochord repair further decreased primary chordae peak force (0.21±0.14 N) to baseline levels (0.20±0.17 N;
P
=0.83), and was associated with lower primary chordae peak force compared with the remodeling (0.34±0.18 N;
P
=0.02) and triangular resectional techniques (0.36±0.27 N;
P
=0.03). Specifically, repair using 2 neochordae resulted in higher peak primary chordal forces (0.28±0.21 N) compared with those using 4 (0.22±0.16 N;
P
=0.02) or 6 neochordae (0.19±0.16 N;
P
=0.002). No difference in peak primary chordal forces was observed between 4 and 6 neochordae (
P
=0.05). Peak forces on the neochordae were the lowest using 6 neochordae (0.09±0.11 N) compared with those of 4 neochordae (0.15±0.14 N;
P
=0.01) and 2 neochordae (0.29±0.18 N;
P
=0.001).

CONCLUSIONS:
Significant biomechanical differences were observed underlying different mitral repair techniques in a translational large animal model. Neochord repair was associated with the lowest primary chordae peak force compared to the remodeling and triangular resectional techniques. Additionally, neochord repair using at least 4 neochordae was associated with lower chordal forces on the primary chordae and the neochordae. This study provided key insights about mitral valve repair optimization and may further improve repair durability.