Computed Tomography-Guided Computational Modeling to Guide Treatment in Aortic Stenosis With Extremely Large Aortic Annulus

A 78-year-old male with severe symptomatic aortic stenosis was assessed by the heart-team as inoperable given the presence of a porcelain ascending aorta. Preprocedural cardiac computed tomography (CT) demonstrated a type-1 Sievers bicuspid aortic valve with a very large annular area at 1021 mm2, perimeter 115 mm, dimensions 37.1 × 36.0 mm and severe raphe and leaflet calcification. (Figure 1a and b). The inter-commissural distance at 4 mm above the annulus was 39.2 mm representing a flared anatomical configuration. Percutaneous implantation of a significantly overfilled balloon-expandable transcatheter heart valve (THV) was considered; however, in the setting of an extremely large aortic annulus beyond the manufacturer recommendations, questions remained regarding procedural safety and feasibility. A combination of CT-guided computational modeling and bench testing was performed to predict valve anchoring, frame expansion, THV leaflet coaptation, and paravalvular regurgitation (PVR). A 29 mm SAPIEN-3 device (Edwards Lifesciences, Irvine, CA) was overfilled by 8 ml and expanded on the bench with high-definition video documenting kinetics of THV expansion and relaxation (Supplemental Video 1). THV frame expansion and height were recorded using digital calipers (Figure 2a and b). The overexpanded THV was placed in a sealed 3D-printed static flow loop with physiological mass pressure (50 mmHg) to simulate leaflet coaptation in diastole. Visual assessment demonstrated complete leaflet coaptation with no leak within the flow loop (Figure 2c). The cardiac CT was analyzed for predictive computational modeling of the SAPIEN-3 balloon-expandable THV. The aortic root and left ventricle were segmented and meshed in Materialize Mimics (Leuven, Belgium). The 29 mm SAPIEN-3 geometry was created from micro-CT measurements with additional data from bench testing (Figure 2). Finite element analysis was performed using Abaqus 2020 (Johnston, USA). Material properties were defined as hyperelastic for native soft tissues, elastic for calcium nodules, and elastic for the stent and balloon which were extracted from previous studies.1Bosmans B. Famaey N. Verhoelst E. Bosmans J. Vander Sloten J. A validated methodology for patient specific computational modeling of self-expandable transcatheter aortic valve implantation.J Biomech. 2016; 49: 2824-2830Crossref PubMed Scopus (31) Google Scholar, 2Holzapfel G.A. Sommer G. Regitnig P. Anisotropic mechanical properties of tissue components in human atherosclerotic plaques.J Biomech Eng. 2004; 126: 657-665Crossref PubMed Scopus (320) Google Scholar, 3Tzamtzis S. Viquerat J. Yap J. Mullen M.J. Burriesci G. Numerical analysis of the radial force produced by the Medtronic-CoreValve and Edwards-SAPIEN after transcatheter aortic valve implantation (TAVI).Med Eng Phys. 2013; 35: 125-130Abstract Full Text Full Text PDF PubMed Scopus (130) Google Scholar The balloon was filled to +8 cc’s above nominal volume to simulate overexpansion of the THV followed by a balloon deflation step to account for tissue recoil (Figure 1c and Supplemental Video 2). CT simulation demonstrated an eccentrically expanded THV with average diameter of 30.4 mm and evidence of anchoring on the leaflet calcification (Figure 3a). PVR was evaluated following the stent deployment using computational fluid dynamics in Ansys Fluent (Canonsburg, USA). A nominal pressure in the aorta of 80 mmHg and 0 mmHg in the ventricle was applied to represent physiological diastolic conditions. The highest velocity PVR jets were predicted to originate anterolaterally (Figure 3b). The patient was successfully treated with a 29 mm SAPIEN-3 THV deployed with 8 ml of additional volume (Figure 1d). Post-dilatation was performed with the same overfilled balloon volume to optimize frame expansion. Intraprocedural transoesophageal echocardiography demonstrated trivial valvular and mild PVR predominately located at the anterolateral aspect of the frame (Figure 3d and Supplemental Video 3). Post-transcatheter aortic valve replacement (TAVR) CT highlighted an eccentrically expanded frame with comparable dimensions to CT modeling (Figure 3c). To our knowledge, this is the largest aortic annulus successfully treated with a THV. It should be emphasized that this single report does not support the routine treatment of extremely large annuli with TAVR, which requires further clinical evaluation. Our case provides new insight into the potential role of CT-guided computational modeling to predict and optimize outcomes in patients undergoing TAVR for complex aortic valve disease. Future studies are needed to assess the ability of CT-guided computational modeling to guide TAVR procedural strategy across the spectrum of annuli size, THV devices, and procedural endpoints. Consent given by the patient for publication of this case. Dr Abdul Ihdayhid is supported by the National Heart Foundation and National Health and Medical Research Council of Australia Scholarships.

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