Background: Fatigue failure of artificial leaflets significantly limits the durability of prosthetic valves. However, the costs and complexities associated with in vitro testing and conventional clinical trials to investigate the fatigue life of leaflets are progressively escalating. In silico trials offer an alternative solution and validation pathway. This study presents in silico trials of prosthetic valves, along with methodologies incorporating nonlinear behaviors to evaluate the fatigue life of artificial leaflets. Methods: Three virtual patient models were established based on in vitro test and clinical trial data, and virtual surgeries and physiological homeostasis maintenance simulations were performed. These simulations modeled the hemodynamics of three virtual patients following transcatheter valve therapy to predict the service life and crack propagation of leaflets based on the fatigue damage assessment. Results and Conclusions: Compared to traditional trials, in silico trials enable a broader and more rapid investigation into factors related to leaflet damage. The fatigue life of the leaflets in two virtual patients with good implantation morphology exceeded 400 million cycles, meeting the requirements, while the fatigue life of a virtual patient with a shape fold in the leaflet was only 440,000 cycles. The fatigue life of the leaflets varied considerably with different implant morphologies. Postoperative balloon dilation positively enhanced fatigue life. Importantly, in silico trials yielded insights that are difficult or impossible to uncover through conventional experiments, such as the increased susceptibility of leaflets to fatigue damage under compressive loading.

With the rise of transcatheter aortic valve-in-valve (ViV) procedures for high-risk patients with degenerated surgical aortic valves, precise positioning of the transcatheter heart valve (THV) within the surgical heart valve (SHV) is crucial for optimal functional outcomes. This study aims to explore the impact of implantation depth on functional outcomes post-ViV in a controlled in vitro setting. This study focused on the impact of valve positioning on fluid dynamics characteristics and subsequent ViV procedural outcomes. Rigorous in vitro experiments measured the structural parameters of the surgical valves, and based on these, the appropriate Taurus Elite valves were selected for pulse flow testing under simulated conditions of varying heart rates and cardiac outputs. Fluid dynamic evaluations were conducted on Taurus Elite THVs in sizes 21, 23, 26, 29 mm and SHVs from two brands: Hancock II (Medtronic, USA) and BalMedic (Balance Medical, China) across a range of diameters. In-depth analysis was performed at a cardiac output (CO) of 5 L/min and heart rate (HR) of 70 bpm, focusing on key metrics such as transvalvular pressure gradient (TVPG), effective orifice area (EOA), and total regurgitation fraction (TRF) at implantation depths of -2.5, 0, 2.5, and 5 mm to gain insights into the dynamic interaction between THV placement and hemodynamic performance. Anchoring force tests were also conducted for SHV-THV combinations at -2.5 and 0 mm depths to ensure safety of implantation. Significant differences were observed in TVPG, EOA, and TRF across various SHV brands and sizes, emphasizing the importance of THV positioning. Specifically, Taurus Elite23 demonstrated superior TVPG performance at various depths compared to Taurus Elite21, indicating a better match with BalMedic19 and Hancock II21, especially at implantation depths ranging from -2.5 to 0 mm. Taurus Elite29 showed the lowest TVPG across all tested depths, making it the preferred choice for BalMedic25 and Hancock II27. These findings highlight the importance of selecting the appropriate THV model and determining the optimal implantation depth for different SHVs. In different surgical valves, both the model and implantation depth of the interventional valve can affect its hemodynamic performance and valve opening-closing morphology. The recommended implantation of the interventional valve as shallowly as possible in this study has guiding significance in clinical valve-in-valve surgeries.