Biomechanics and Risk of Coronary Obstruction in Transcatheter Aortic Valve Replacement
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Sivakumar, Sri Krishna
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Abstract
TAVR has rapidly evolved into the preferred method of aortic valve replacement, taking over SAVR in all age groups due to expansion of indication to all patients with aortic stenosis and great outcomes in long term studies. However, several complications have been reported that may occur as a result of TAVR and therefore careful procedural planning becomes essential to ensure good patient outcomes. Computational modeling can provide accurate visualizations of the post-TAVR configurations of the device and the native anatomy to extract information about the potential for complications. However, computational modeling of TAVR is not regularly used in clinical practice and one of the reasons could be the lack of data on validation of the computational models in predicting the device deformation in a range of clinical anatomies. To treat patients where the only treatment option is TAVR, surgeons are adopting strategies that help with mitigating the risk of complications such as changing the deployment depth, balloon volume or post-dilatation of the bioprosthesis and laceration of the native or bioprosthetic valve leaflets. However, it is not fully understood the impact of such adaptations on the device itself or the potential for other complications. Coronary obstruction is a serious procedural complication associated with high mortality rates. Proper standardized assessment of the risk of coronary obstruction during procedural planning is necessary and current clinical guidelines fail to achieve sufficient accuracy in predicting the complication. The studies contained in this thesis document aim to resolve these clinical questions and deficiencies with an overarching goal of adding to the knowledge of biomechanics of TAVR in native and bioprosthetic aortic valves.
In the first aim, development and clinical validation of deployment models of TAVR valves currently in use clinically in patients with failed native tricuspid aortic valves is described. Simulations of the THV deployment using finite element methods showed excellent agreement with the post-TAVR CT images. Adjustments to the deployment methods were tested. Changes to the implantation depth had no impact on the THV expansion or shape in native aortic valves. Overfilling of the deployment balloon in SAPIEN showed improvement in device expansion and underfilling showed an increase in potential for leaflet thrombosis. Post-dilatation of Evolut increased expansion in the functional region. In the second aim, the developed models were applied to predict deformation in valve-in-valve TAVR. Lower deployment worsened the functional area in Evolut, and a higher implant decreased inflow area for the SAPIEN. Both devices were found to expand better with laceration of bioprosthetic aortic valve leaflets. In the third aim, coronary obstruction predictive models based on THV deployment simulations were developed and validated against post-TAVR outcomes in both native and valve-in-valve TAVR. The impact of transcatheter valve type on the risk of coronary obstruction was studied. The outcomes of this thesis can help clinicians better visualize transcatheter valve deformations in native and valve-in-valve TAVR, better understand the impact of procedural adaptions and optimize the selection of THV to minimize the risk of coronary obstruction in every patient.
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Date
2023-08-22
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Dissertation