Patient-specific compliant simulation framework informed by 4DMRI-extracted pulse wave Velocity: Application...

Area of Science:

• Biomedical Engineering
• Cardiovascular Imaging
• Computational Fluid Dynamics

Background:

• Type-B aortic dissection (TBAD) poses significant risks, often treated with thoracic endovascular aortic repair (TEVAR).
• Accurate patient-specific computational fluid dynamics (CFD) simulations are crucial for assessing post-TEVAR hemodynamics and predicting complications.
• Current simulation methods may not fully capture the complex biomechanics of the dissected aorta.

Purpose of the Study:

• To develop and validate a novel computational framework integrating 4D flow MRI-derived Pulse Wave Velocity (PWV) into patient-specific CFD simulations for post-TEVAR Type-B aortic dissection.
• To compare the accuracy of regional PWV (RPWV)-based distensibility versus area-based distensibility for simulating aortic wall mechanics.
• To evaluate the impact of different stiffness estimation methods on hemodynamic predictions, including wall shear stress (WSS) and thrombosis risk.

Main Methods:

• A computational framework was developed using 4D flow MRI (4DMRI) data to extract PWV and define patient-specific thoracic aortic geometry, 3D inlet velocity profiles (IVP), and dynamic outlet boundary conditions.
• A moving boundary method (MBM) was employed to simulate aortic wall displacement.
• Aortic wall stiffness was estimated using two approaches: area-based distensibility and RPWV-based distensibility, with fine-tuning to match in vivo data.
• CFD simulations were performed for Type-B aortic dissection (TBAD) patients post-thoracic endovascular aortic repair (TEVAR).

Main Results:

• Predicted pressures and outlet flow rates closely matched target values (within 2.3%).
• RPWV-based simulations demonstrated superior accuracy in replicating in vivo hemodynamics compared to area-based simulations.
• Systolic flow reversal ratios (SFRR) were accurately captured; however, significant differences (up to 60%) in in-plane rotational flow (IRF) were observed.
• Disparities in predicted wall shear stress (WSS)-based indices, particularly endothelial cell activation potential (ECAP), were noted between the two methods.
• The RPWV-driven simulation identified a high ECAP (>1.4 Pa⁻¹) at the isthmus, indicating potential thrombosis risk not predicted by the area-based method.

Conclusions:

• The proposed pipeline, leveraging RPWV from 4DMRI for CFD simulations, provides a validated and comprehensive approach for assessing post-TEVAR TBAD.
• RPWV-based distensibility is a more accurate method for estimating aortic wall stiffness and predicting in vivo hemodynamics than area-based distensibility.
• This advanced simulation framework facilitates better surgical decision-making and aids in the prediction of potential complications like thrombosis and aortic growth.