Are All Flexible Mitral Annuloplastic Rings the Same? An in Vivo Study

Objectives: The overall purpose of this experimental study is to assess the biomechanical properties of two different flexible mitral annuloplasty rings (Medtronic Simulus and Medtronic Duran) in comparison to a completely rigid annuloplasty ring and the native valve. The evaluation and comparison of the rings will be based on 3D geometry of the mitral annulus, leafletcoaptation geometry and leaflet curvature during the heart cycle. Force quantification and distribution on the valve will also be evaluated.
Material and methods: The two different types of annuloplasty bands and the rigid ring will be surgically implanted and tested in an acute porcine model. Twenty animals (80kg) will be used for testing, equally distributed into 4 groups; a Duran group (flexible), a Simulus group (flexible), a Classic group (fully rigid) and a native group. Before and after ring implantation, the dynamic 3D geometry and leaflet coaptation will be assessed by sonomicrometry and by 2D echocardiography, respectably. Dedicated force transducers attached directly to the annuloplasty rings will measure annular deformational forces in the septal-lateral and commissural dimensions. A comprehensive analysis of the impact of flexible properties of the annuloplasty rings on mitral leaflet motion and stress distribution will be performed from simultaneous recordings and calculations of the mentioned parameters throughout the cardiac cycle. Results: Pending.
Conclusion: We hypothesize that the Medtronic Simulus ring, compared to the Medtronic Duran Ring, provide better support of the mitral annulus by reducing annular motion and the resulting deformational forces of mitral annulus during the cardiac cycle.