Predicting Hemodynamic and Biomechanical Implications of MitraClip Transcatheter Edge-To-Edge Therapy on Treatment of Functional Mitral Regurgitation
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Gooden, Shelley Chee-Mei
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Abstract
Mitral regurgitation (MR) is the leading cause of heart valve disease, where moderate MR is present in at least 1.7% of the adult population, increasing to 11.7% in those age 75 years and older. MR occurs when the two leaflets of the mitral valve (MV) do not close properly when they should. Left untreated, MR severity can increase and lead to heart failure. Patients with moderate-to-severe or severe MR who remain symptomatic despite optimal medical therapy and are deemed at high surgical risk by a heart team are candidates for transcatheter edge-to-edge repair with the commercially available MitraClip. Though clinical trials show promising outcomes, challenges with MitraClip use include sufficient reduction of MR while preventing elevated MV pressure gradient (MVG), as these two unfavourable outcomes worsen prognosis. Optimal use and predictive modeling of MVG post-MitraClip is not well defined, especially with four device sizes available in the current G4 generation. Further guidelines to optimize MitraClip usage is needed, as transcatheter MV repair has overtaken surgical repair in the United States. MitraClip use for degenerative MR is well established; however, questions remain for functional MR (FMR). The impact of MitraClip size was first assessed using an excised porcine model, where atrial and ventricular FMR were studied. Residual regurgitation with device size was found to be dependent upon baseline MR conditions, and post-therapy MVG was found to increase most with the largest device size. A parameterization approach was developed to simplify human MV geometries, and MitraClip placement was simulated. Post-MitraClip MVG was found to be greatest for smaller MVs and for larger device size. Forward flow measured by clinical means (CW Doppler) and by engineering means (conservation of mass) showed strong correlation. Applying this in vivo, a post-MitraClip MVG predictive model was developed, which showed good agreement to in vivo FMR outcomes. The outcomes of this thesis can help clinicians assess patient MitraClip candidacy and help optimize MitraClip treatment strategies by predicting post-therapy MVG.
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2023-03-14
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Dissertation