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.

Comparison of the Dacron ring and suture annuloplasty for aortic root repair: an in vitro evaluation.

OBJECTIVES: Increasing evidence shows that annular stabilization is essential in most aortic valve repair procedures. However, a standardized comparison of the 2 commonly used annuloplasty procedures is lacking. We hypothesized that the Dacron ring is more rigid than the polytetrafluoroethylene suture, whereas both procedures decrease annular dimensions. The aim of this study was to compare the biomechanical properties of the ring and suture techniques with native aortic roots in vitro. METHODS: Eighteen aortic roots explanted from 80-kg pigs were randomized into a Dacron ring group, a suture annuloplasty group and a native control group. Each sample was tested in a pulsatile in vitro model with a force transducer attached to the aortic annulus to obtain radial force measurements, and annular dynamics was evaluated using 2-dimensional echography. RESULTS: Among the 2 annuloplasty procedures, only the Dacron ring group provided a significant reduction in the annular diameter compared with the native group (P < 0.006). Both annuloplasty procedures significantly reduced the geometric orifice area, tenting area and sinus diameter while increasing the coaptation length compared with the native group. Systolic annular distension was retained between groups, although the total radial forces were significantly reduced in the procedure groups compared with the native group (ring 1.07 ± 0.45 N, suture 1.13 ± 0.39 N and native 3.55 ± 1.34 N, P < 0.001). CONCLUSIONS: Although both annuloplasty procedures increase coaptation length and decrease geometric orifice area, a significant downsizing of the annulus was achieved using the Dacron ring only. The systolic annular distension was similar to the native aortic root, whereas the radial annular forces were evenly decreased by both annuloplasty procedures. Long-term studies are needed to disclose any difference in long-term effect of the annuloplasty procedures.