Optimized mitral annuloplasty ring design reduces loading in the posterior annulus

Abstract

Objective: The study objective was to develop a novel annuloplasty ring with regional flexibility and assess its suture force dynamics in healthy ovine subjects compared with fully rigid or fully flexible rings.

Methods: Materially heterogeneous rings were created with rigid anterior and posterior, and flexible commissural segments. These rings were created to match the geometry of the Profile 3D ring (Medtronic, Minneapolis, Minn). Each ring was instrumented with 10 force transducers to measure cyclic suture forces (F_C) and undersized annuloplasty was performed in 6 healthy ovine subjects. Each F_C was recorded and examined for cardiac cycles reaching a maximum left ventricular pressure of 100, 125, and 150 mm Hg. F_C was compared with previously reported values from fully rigid Profile 3D and fully flexible prototype rings.

Results: Relative to the fully rigid ring, the heterogeneous ring exhibited 48% reduction in F_C at its commissural (rigid vs heterogeneous: 1.80 ± 0.94 N vs 0.95 ± 0.52 N; P < .001) and 32% reduction in posterior (1.90 ± 0.92 N vs 1.29 ± 0.91 N; P < .001) regions, but not in its anterior region (2.45 ± 1.21 N vs 2.23 ± 1.22 N; P = .279). Relative to the fully flexible ring, the heterogeneous ring exhibited no significant differences in F_C in any region.

Conclusions: The reduced F_C of the heterogeneous ring relative to the fully rigid ring suggests a promising approach to reduce suture loading while preserving the annular remodeling capability of fully rigid rings. Future studies in diseased subjects are necessary to explore repair effectiveness of this ring.

Keywords: mitral annuloplasty; mitral regurgitation; mitral repair; ring dehiscence; suture forces.