Modeling isovolumetric phases in cardiac flows by an Augmented Resistive Immersed Implicit Surface method.

Area of Science:

• Computational fluid dynamics
• Biomedical engineering
• Cardiovascular modeling

Background:

• Simulating heart function with computational fluid dynamics (CFD) faces challenges during isovolumetric phases.
• Closed valves during these phases can lead to undefined ventricular pressure and spurious oscillations, impacting physiological accuracy.
• Current methods often neglect isovolumetric phases or require prescribed valve timing.

Purpose of the Study:

• To introduce a modified Resistive Immersed Implicit Surface (RIIS) method, termed Augmented RIIS (ARIIS), for accurate simulation of isovolumetric phases in hemodynamics.
• To extend the ARIS method to non-body-fitted meshes for improved valve dynamics modeling.
• To enable natural opening and closing of cardiac valves within CFD simulations.

Main Methods:

• Modification of the RIIS method by incorporating a reaction term to capture pressure transients during isovolumetric phases.
• Extension of the ARIS method to handle non-body-fitted meshes, suitable for complex geometries.
• Validation using benchmark problems and application to a realistic left heart geometry.

Main Results:

• The ARIIS method successfully captures pressure transients during isovolumetric phases, unlike the standard RIIS method.
• Simulations demonstrate the ability of ARIIS to handle cardiac valve dynamics without requiring prescribed opening or closing times.
• The method proved effective in fluid dynamics simulations of a realistic left heart model.

Conclusions:

• The ARIIS method provides a robust solution for simulating isovolumetric phases in cardiac CFD.
• This advancement allows for more physiologically realistic modeling of heart function and valve dynamics.
• ARIIS eliminates the need for externally imposed valve timing, enhancing simulation autonomy.