Simultaneous 3D Quantification of Fluid-Structure Interaction in a Patient-Averaged Left Ventricle: A Lagrangian...

Area of Science:

• Biomedical Engineering
• Fluid Dynamics
• Computational Biology

Background:

• Experimental validation of dynamic left-ventricular (LV) models is challenging due to difficulties in simultaneously measuring 3D wall motion and intraventricular flow.
• Existing methods often struggle to capture the complex fluid-structure interactions (FSI) within the beating heart.

Purpose of the Study:

• To develop and validate a novel experimental framework for high-fidelity, time-resolved 3D reconstructions of LV wall motion and Lagrangian flow.
• To quantify spatial distributions of wall shear stress (WSS) and assess the reliability of Eulerian proxies for intraventricular transport.

Main Methods:

• Integration of deep-learning segmentation (SAM2) with 3D Particle Tracking Velocimetry (3D-PTV) and multi-media ray tracing.
• Creation of a compliant LV model capable of simulating FSI at physiological heart rates.
• Quantification of FSI metrics including TAWSS, OSI, and RRT, and comparison with Lagrangian residence time (LRT).

Main Results:

• A moderate inverse relationship was observed between regional wall acceleration and time-averaged wall shear stress (TAWSS).
• Relative residence time (RRT) showed weak correspondence with directly measured Lagrangian residence time (LRT).
• Surface-based Eulerian metrics may not reliably represent volumetric transport in dynamic cardiac chambers.

Conclusions:

• The developed framework provides a high-fidelity "physical twin" for studying LV dynamics and FSI.
• Lagrangian descriptors are valuable for characterizing intraventricular transport and assessing thrombogenic risk.
• Experimental findings serve as a benchmark for computational FSI simulations.