Feasibility and Performance Analysis of Redo-Transcatheter Aortic Valve Replacement: A Patient-Specific In-silico Study

Introduction: Transcatheter aortic valve replacement (TAVR), a minimally invasive procedure, has demonstrated equivalent hemodynamic performance compared to surgical aortic valve replacement (SAVR) and has become the standard procedure for high- and intermediate-risk aortic stenosis patients. Recently, TAVR has also been approved for use in low-risk patients. However, prosthetic TAVR leaflets are inherently subjected to degeneration [1]. Recent clinical studies have found evidence of early leaflet thrombosis formation [2] and thus may be associated with an earlier risk of structural valve degeneration. Hence, durability remains one of the major concerns for TAVR technology. This evidence of thrombosis and rapid degeneration of prosthetic valves poses a significant risk to the increasing number of young and low-risk TAVR recipients, necessitating repeat intervention. Transcatheter aortic valve-in-transcatheter aortic valve (TAV-in-TAV) or redo-TAVR is being considered as a potential treatment of choice for transcatheter heart valve (THV) degeneration, which has shown success in addressing suboptimal outcomes. However, the current lack of data is preventing redo-TAVR from being established as a safe and viable procedure. Recently, an in-vitro study has suggested a combination-dependent hemodynamic performance of redo-TAVR in an idealized aortic root [3]. Performance of TAV-in-TAV may also depend upon factors including the diseased patient-specific anatomy and the complex flow domain formed by the native leaflets and two TAVR device prostheses. A comprehensive structural and hemodynamic performance analysis, along with thrombogenic risk assessment of different TAV-in-TAV combinations in a patient-specific scenario, may provide vital insights into the feasibility of redo-TAVR procedures and help identify the optimal combination.


Materials and Methods: A patient with a 23.5mm CT-derived annular diameter was selected for this study. The patient model was reconstructed (Figure 1a) following our previous study [4]. The most widely used self-expandable (SE) Evolute (Medtronic plc, Minneapolis, MN, USA) and balloon-expandable (BE) Sapien (Edwards Lifesciences, Irvine CA) TAVR systems were considered for this study where 26 mm Evolut R and Sapien 26 mm TAVR devices were selected as the first TAVR devices and the most recent versions of Evolut and Sapien TAVR systems (26 mm Evolut Pro and 26 mm Sapien 3 Ultra) were used as the index TAVR devices. TAVR implantation simulations were then performed following our previous studies (Figure 1b) [5] using Abaqus Explicit 2019 (SIMULIA, Dassault Systèmes, Providence, RI). The selected TAVR devices result in four TAV-in-TAV combinations (Figure 1c) including - i) SE-in-BE, ii) BE-in-BE, iii) BE-in-SE, and iv) SE-in-SE. A 2-way coupled fluid-structure interaction (FSI) using a body-fitted sub-grid geometry resolution (SGGR) method was then performed following our previous study [6] to analyze the hemodynamic performance of the TAV-in-TAV combinations. FSI simulations were performed (Figure 1d) coupling the fluid solver, FlowVision 3.12 (Capvidia NV, Leuven, Belgium), with Abaqus Explicit 2019. The thrombogenic risk assessment analysis was performed following our previously developed and validated technique where Lagrangian particles representing platelets are injected into the flow and the stress accumulation (SA) is computed along each particle trajectory. The SA data is then collapsed into a probability density function (PDF) to compute the “thrombogenic footprint” [7] for each TAV-in-TAV combination.


Results:Structural and hemodynamic analyses were performed following TAV-in-TAV simulations. The SE-in-SE combination demonstrated the highest eccentricity and the narrowest coronary access. The combinations involving SE devices (BE-in-SE, and SE-in-BE) demonstrated limited coronary access. SE-in-BE demonstrated the narrowest opening at the annular plane. BE-in-BE demonstrated superior performance from the structural perspective with the widest coronary access and opening at the annular plane. However, BE-in-SE demonstrated 40% leaflet overhang which may impact the hemodynamic performance. Initial results from the hemodynamic analysis demonstrated combination-specific performance. Further investigations are being performed to identify the optimal TAV-in-TAV device combination with minimal thrombogenic risk on a patient-specific basis.


Discussion: Successful implantation and optimal hemodynamic performance of redo-TAVR requires careful assessment of specific device characteristics due to the technical and structural differences in TAVR prostheses including mode of deployment (BE and SE), valve function (intra-annular and supra-annular), and valve design (skirt and stent frame design, and height). Patient-specific features and the interaction between the second/index THV with the patient's anatomy also play crucial roles in the performance of the redo-TAVR procedure. Therefore, patient-specific preprocedural planning is critical in minimizing peri-procedural and post-procedural risk [8]. In this study, we addressed the aforementioned clinical concerns by performing a set of computational analyses starting from finite element-based TAVR deployment in patient-specific models to FSI-based hemodynamic analysis coupled with particle stress accumulation analysis that accounts for blood flow stasis and exposure to high shear. Using these techniques, we analyzed the feasibility and performance of TAV-in-TAV combinations. The initial results illustrated the pros and cons of different TAV-in-TAV combinations in a patient model where BE-in-BE seems to be the optimal combination of redo-TAVR. However, further analysis of the hemodynamic effect of leaflet overhang associated with BE-in-BE is required.


Conclusions: This study presented a thorough computational protocol to analyze patient-specific structural and hemodynamic performance and assess the thrombogenic risk of TAV-in-TAV combinations and generated knowledge addressing current clinical concerns on THV degeneration and its potential solution, redo-TAVR. These techniques can potentially be used to aid the clinicians in lifetime management of TAVR patients through optimal first and second THV selection.

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