In-Vivo Evaluation of Flexible Mitral Annuloplasty Rings: Are They All the Same?

BACKGROUND: Currently, several different flexible mitral annuloplasty rings are available, and their efficacy for surgical repair of the mitral valve is, in general, considered equal. However, clinical experience indicates differences in remodeling capacity that have not yet been quantitatively assessed. The study aim was to compare the biomechanical properties of two commonly used flexible mitral annuloplasty rings in an acute pig model.

METHODS: Medtronic Simulus Flex (n = 5) and Medtronic Duran AnCore (n = 7) flexible mitral annuloplasty rings were implanted in pigs (bodyweight 80 kg). The native mitral valve was used as a reference (n = 7). Mitral annular dynamics and dimensions were assessed using 11 sonomicrometry crystals placed in the mitral apparatus. A dedicated force transducer was used to detect deformational force transmission between the annuloplasty ring and the mitral annulus.

RESULTS: Cyclic changes in mitral annular circumference and commissure-commissure distance were significantly reduced in the Simulus Flex group compared to the Duran AnCore group (p = 0.025 and p <0.01, respectively). In the Simulus Flex group, smaller deformational forces were recorded compared to the Duran AnCore group, but the difference was not statistically significant (p = 0.52 and p = 0.06 for the septal-lateral and the commissure-commissure force measurements, respectively).

CONCLUSIONS: The Simulus Flex ring showed significantly more remodeling capacity than the Duran AnCore ring, but the latter ring preserved the natural dynamics of the mitral valve to a greater degree. Insights into these biomechanical differences may facilitate strategies for surgical reconstruction in degenerative mitral valve disease, especially in patients with excessive amounts of tissue and who are at risk of systolic anterior motion of the mitral valve.