Investigation of hemodynamic bulk flow patterns caused by aortic stenosis using a combined 4D Flow MRI-CFD framework

Area of Science:

• Cardiovascular fluid dynamics
• Biomedical engineering
• Medical imaging analysis

Background:

• Aortic stenosis (AS) causes abnormal supra-valvular blood flow.
• Altered flow patterns can damage red blood cell (RBC) membranes.
• Patient-specific computational modeling can elucidate these flow dynamics.

Purpose of the Study:

• To investigate patient-specific supra-valvular flow patterns in severe AS.
• To compare pathological flow with healthy flow using 4D Flow MRI and CFD.
• To identify flow characteristics responsible for RBC membrane damage.

Main Methods:

• Subject-specific computational models of aortic geometries were created from medical imaging.
• 4D Flow MRI data provided boundary conditions for CFD simulations.
• In-silico results were validated against in-vivo data (R² = 0.9).
• Flow fields were analyzed for shear stress, helicity, and turbulent kinetic energy.

Main Results:

• A pathological high shear stress region in AS flow increased by 125% compared to healthy flow.
• The physiological bihelical flow structure was lost in AS, replaced by left-handed helicity.
• Increased turbulent kinetic energy was observed in areas of left-handed helicity.

Conclusions:

• Validated 4D Flow MRI-based CFD models reveal significant differences between AS and healthy flow.
• Altered turbulent and helical structures in AS bulk flow contribute to increased forces on RBCs.
• These forces may cause increased RBC membrane damage in patients with aortic stenosis.