Biophysical Society Thematic Meeting | Canterbury 2023

Towards a More Perfect Union: Multi-Scale Models of Muscle and Their Experimental Validation

Tuesday Speaker Abstracts

FSGE: A COMPUTATIONAL MODEL FOR EQUILIBRATED CARDIOVASCULAR FLUID-SOLID-GROWTH INTERACTION Martin R Pfaller 1,2,3 ; Marcos Latorre 4 ; Erica L Schwarz 6 ; Fannie M Gerosa 1,3 ; Jason M Szafron 1 ; Jay D Humphrey 5 ; Alison L Marsden 1,2,3 ; 1 Stanford University, Pediatrics, Stanford, CA, USA 2 Stanford University, Maternal & Child Health Research Institute, Stanford, CA, USA 3 Stanford University, Institute for Computational and Mathematical Engineering, Stanford, CA, USA 4 Universitat Politècnica de València, Center for Research and Innovation in Bioengineering, Valencia, Spain 5 Yale School of Medicine, Vascular Biology and Therapeutics Program, New Haven, CT, USA 6 Stanford University, Bioengineering, Stanford, CA, USA Growth and remodeling (G&R) are commonly triggered mechanically through fluid-structure interaction by a combination of pressure-induced intramural stress and flow-induced wall shear stress. Previous G&R models rely on simplifying assumptions for fluid dynamics of blood inside the vessel. We propose to combine fluid-structure interaction and G&R in a novel fluid-solid growth (FSGe) framework using a mechanobiologically equilibrated version of the constrained mixture theory. We solve the incompressible Navier-Stokes equations to obtain velocity and pressure inside the blood vessel. At the fluid-solid interface, we pass local fluid pressure and wall shear stress to our large-deformation solid G&R model. As the solid model, we use a fast and efficient formulation of the constrained mixture theory, assuming that each G&R state is mechanobiologically equilibrated. A shear-to-intramural gain ratio controls the importance of wall shear stress and intramural stress stimuli. Both fields are coupled in a partitioned scheme, separating fluid and solid time scales (seconds vs. weeks). The computational cost of our coupling scheme is comparable to a fluid-structure-interaction simulation with a hyperelastic solid material. We compare our coupled FSGe method to G&R models with different fluid approximations for pressure and wall shear stress. Our examples include aneurysmal formation, stenosis formation, and distortions of blood flow for various Reynolds numbers. Simplified fluid dynamics in cardiovascular G&R models can provide a good approximation in many scenarios. However, we show that local fluid dynamics can significantly influence the long-term G&R state in blood vessels. This work was supported by NIH Grants K99HL161313, R01HL139796, R01HL159954, the Additional Ventures Foundation Cures Collaborative, and the Stanford Maternal and Child Health Research Institute.

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