Evaluating Novel Annuloplasty Ring Designs in a Pathophysiological Animal Model

Annuloplasty ring dehiscence post ischemic mitral regurgitation is an extensively studied mode of failure. This study aimed to compare annuloplasty ring designs of varying stiffness and investigate annular forces to understand mechanisms that may mitigate likelihood of ring dehiscence.

Force transducers were attached to 5 types of rings-rigid, flexible, COM-Flex, POST-Flex, and ALPM-Flex-having varying stiffness. After undersized ring implantation in diseased animals (N = 31), ring suture forces (F_C(avg)) were measured for peak left ventricular pressures of 100, 125, and 150 mm Hg.

In normotensive animals, anterior F_C(avg) was highest in POST-Flex rings (2.2 ± 0.73 N). Posterior F_C(avg) was considerably lower in flexible (0.7 ± 0.10 N) compared with rigid (1.6 ± 0.27 N) and COM-Flex (1.1 ± 0.13 N) rings. POST-Flex rings had notable differences between anterior F_C(avg) (2.2 ± 0.73 N) and posterior F_C(avg) (1.4 ± 0.38 N). ALPM-Flex and COM-Flex rings had anterior F_C(avg) of 1.6 ± 0.47 N and 1.6 ± 0.25 N, and posterior F_C(avg) of 1.2 ± 0.45 N and 1.1 ± 0.13 N, respectively.

Results demonstrate trends in suture forces and their spatial variation. COM-Flex was most effective in distributing forces away from posterior annulus. Despite POST-Flex having large material heterogeneity, average posterior force was similar to rigid rings. Results shown in this study provide an atlas of data on how variable annular loading is and the complexity of both understanding loads and developing devices to sustain them.