Mitral Valve Annuloplasty
Mitral valve annuloplasty is a common surgical technique used in the repair of a leaking valve by implanting an annuloplasty device. To enhance repair durability, these devices are designed to increase leaflet coaptation, while preserving the native annular shape and motion; however, the precise impact of device implantation on annular deformation, strain, and curvature is unknown. In this article, we quantify how three frequently used devices significantly impair native annular dynamics. In controlled in vivo experiments, we surgically implanted 11 flexible-incomplete, 11 semi-rigid-complete, and 12 rigid-complete devices around the mitral annuli of 34 sheep, each tagged with 16 equally spaced tantalum markers. We recorded four-dimensional marker coordinates using biplane videofluoroscopy, first with device and then without, which were used to create mathematical models using piecewise cubic splines. Clinical metrics (characteristic anatomical distances) revealed significant global reduction in annular dynamics upon device implantation. Mechanical metrics (strain and curvature fields) explained this reduction via a local loss of anterior dilation and posterior contraction. Overall, all three devices unfavorably caused reduction in annular dynamics. The flexible-incomplete device, however, preserved native annular dynamics to a larger extent than the complete devices. Heterogeneous strain and curvature profiles suggest the need for heterogeneous support, which may spawn more rational design of annuloplasty devices using design concepts of functionally graded materials.
KeywordsMitral annulus Mitral regurgitation Annuloplasty Strain Curvature Dynamics
The authors thank Paul Chang, Eleazar P. Briones, Lauren R. Davis, and Kathy N. Vo for technical assistance; Maggie Brophy and Sigurd Hartnett for careful marker image digitization; and George T. Daughters III for computation of 4D data from biplane 2D marker coordinates. This study was supported in part by the Deutsche Herzstiftung, Frankfurt, Germany, Research Grant S/06/07 to Wolfgang Bothe; by the U.S.-Norway Fulbright Foundation, the Swedish Heart-Lung Foundation, and the Swedish Society for Medical Research to John-Peder Escobar Kvitting; by the Western States Affiliate American Heart Association Fellowship to Julia C. Swanson; by US National Institutes of Health grants R01 HL29589 and R01 HL67025 to D. Craig Miller; and by the US National Science Foundation grant CAREER award CMMI-0952021 to Ellen Kuhl.
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