The following are key points to remember from a state-of-the-art guide to transcatheter aortic valve (TAV) design and systematic planning for a redo-TAV (TAV-in-TAV) procedure:

1. For the performance of redo transcatheter aortic valve (TAV) procedures (valve-in-valve TAV replacement [TAVR]), it is necessary to understand the design features of various TAV devices, their compatibility, standardized sizing, and optimal placement.
2. TAV types:
• The basic design of each TAV device includes a stent frame, leaflets, and skirt.
• TAV label sizing is not standardized.
• In general, all short valves are intra-annular and most (but not all) tall valves are supra-annular; tall valves are self-expanding valves (SEV), whereas short valves are either balloon-expandable (BEV) or mechanically expandable (MEV).
3. Terminology: Proposed standardized nomenclature for redo-TAV workup includes:
• Leaflet overhang is the portion of the leaflets from the index (original) TAV that extends above the second (redo) TAV following the redo procedure.
• The neoskirt is the portion of the redo-TAV combination covered by the inner skirt and the deflected-open leaflets of the index TAV.
• The neoskirt plane (NSP) is defined as the plane at the top of the neoskirt, which is unique to the index and redo-TAV combination and might be at multiple heights.
• The coronary risk plane (CRP) is defined as the plane at the base of the lowest patent coronary ostium. (When the NSP is at or below the CRP, there will be no risk to the coronaries with redo-TAV.)
• The valve-to-aorta (VTA) distance, defined as the distance between the aorta and either the index TAV or a circle simulating the size of the second TAV, is used to help identify the risk of coronary obstruction.
• Commissural and coronary alignment of the index TAV refers to the relationship between the index TAV and the native coronary commissures.
4. TAV design: Specific TAV designs relevant to redo-TAV are reported for:
• BEVs (Sapien XT, Sapien 3, and Sapien Ultra, Myval).
• MEVs (Lotus and Lotus Edge).
• SEVs (Portico and Navitor, CoreValve, Evolut R/PRO/PRO+/FX, Acurate neo/neo2, Allegra).
5. Computed tomography (CT) planning: A systematic approach can be applied to the analysis and interpretation of CT images for redo-TAV. The key goals are:
• Choose the appropriate redo TAV device type and size, considering the index TAV in vivo dimensions, the native annular/left ventricular outflow tract dimensions, and the extent of calcification to mitigate the risk of root injury.
• Determine the risks of coronary obstruction and sinus sequestration, and the potential requirement for coronary protection and/or leaflet modification.
• Pursue the best possible hemodynamic performance of the redo-TAV with optimal implant height.
6. Step-by-step CT analysis: Each index-TAV/redo-TAV combination is unique; the authors describe a step-by-step approach for CT-based pre-procedural planning:
• Confirm index TAV type, size, and characteristics.
• Identify the CRP and its relation to the index TAV.
• Select a second TAV.
• Assess ideal and acceptable levels of NSP.
• Choose the NSP height of implant and analyze its relationship with the CRP.
• Determine sizing of the second TAV.
• Perform coronary risk assessment.
• Assess options to mitigate coronary risk.
• Prepare an inclusive and descriptive report.
7. Future directions: Some aspects of the TAV-in-TAV procedure require additional testing and validation, including:
• Assess the adequacy of the strategy that employs in vivo CT sizing of the second TAV.
• Compare predicted and observed VTA distances and assess coronary access and perfusion.
• Assess the implications of leaflet overhang and its effects on hemodynamics and durability of redo-TAV using tall devices.
• Understand the relationship between the alignment of second TAV commissures with the index TAV on coronary access.
• Using post-second-TAV CT, assess the validity of simulation software to help guide procedural risk and expansion of the second TAV.

Clinical Topics: Cardiac Surgery, Invasive Cardiovascular Angiography and Intervention, Noninvasive Imaging, Interventions and Imaging, Computed Tomography, Nuclear Imaging

Keywords: Tomography, Emission-Computed, Transcatheter Aortic Valve Replacement

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