Verification of a Fluid-Structure Interaction Model for Aortic Stenosis Through Comparison With In Vitro Experiments

Aortic stenosis (AS) severity is typically assessed by measuring pressure drop across the aortic valve in rest. However, this flow-dependent metric is influenced by patients' cardiac function, complicating clinical decision-making on valve replacement. Moreover, assessment during rest does not reflect valvular dynamics under higher flow rates (e.g., during exercise), and may underestimate severity in moderate AS patients. Patient-specific Fluid-Structure Interaction (FSI) modelling offers a promising, non-invasive method to simulate valve dynamics under varying conditions, independent of pressure exerted by the left ventricle. Therefore, this study aimed to experimentally verify an aortic stenosis FSI model using a patient-specific aortic valve geometry, including calcifications, across flow conditions ranging from rest to exercise. To achieve this goal, in vitro experiments were conducted using a mock-loop circulatory system with patient-specific silicone rubber valve models, both calcified and non-calcified. These experiments were replicated in FSI simulations. Overall, good agreement was observed between simulated and experimental results for the non-calcified valve in terms of mean transvalvular flow (5% error on average) and aortic valve area (AVA) (10% error on average). Discrepancies were more pronounced in the calcified valve due to added complexity and uncertainty introduced by calcifications (8% and 7% error on average for mean transvalvular flow and AVA, respectively). For clinical implementation, two key challenges remain: (1) developing efficient and reliable methods to estimate valve leaflet material properties and pre-stress, and (2) verifying the model against a broader range of in vitro data, followed by validating it against real, clinical data. Despite the remaining challenges, this study demonstrated the feasibility of using FSI models as a complementary, non-invasive tool to assess AS severity and support clinical decision-making on valve replacement.