Changes In The In Vivo Functional State Of The Mitral Valve In Edge-to-edge Leaflet Approximation
Natalie Simonian1, Joseph H. Gorman, III2, Robert C. Gorman2, Sneha Vakamudi3, Mark J. Pirwitz3, Michael S. Sacks1.
1University of Texas at Austin, Austin, TX, USA, 2University of Pennsylvania, Philadelphia, PA, USA, 3Ascension Texas Cardiovascular, Austin, TX, USA.
Objectives: Mitral valve leaflet approximation techniques, such as the MitraClip (Abbott Inc.) procedure, have become increasingly common to correct ischemic mitral valve regurgitation (IMR). While initial short-term MitraClip outcomes have been encouraging, the long-term efficacy of this procedure, as well as patient-specific guidelines for optimization, remain unknown. Our overall objective is to develop a robust understanding of the functional consequences of leaflet approximation using readily available imaging data to accurately assess and predict the efficacy and longevity of the MitraClip procedure for individual patients.Methods: Real-time three-dimensional echocardiography (rt-3DE) images of ovine mitral valves (MV) during the Alfieri stitch procedure were segmented and analyzed using our extensively validated in-vivo strain estimation pipeline. Rt-3DE images were also acquired of patients' MVs before and after the MitraClip procedure, and similarly processed to produce strain maps of the local circumferential and radial strain across the entire valve.Results: We found evidence of significant distortion in leaflet geometry due to leaflet approximation, with an overall increase of radial strain and a decrease of circumferential strain. Furthermore, stress concentrators were observed in both the circumferential and radial directions, particularly in the leaflet segments where the stitch or clip was placed.Conclusions: Leaflet approximation clearly induces major alterations in MV leaflet strain and stress behaviors. This work confirms that such techniques dramatically alter the MV functional behaviors, which may elucidate the underlying reasons long-term MV remodeling occurs in response to the observed stress concentrations, possibly leading to limited repair durability.
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