An electromechanics-driven fluid dynamics model for the simulation of the whole human heart

TL;DR

The paper develops a high-fidelity, electromechanics-driven fluid dynamics model for the whole human heart by coupling a four-chamber EM model to a 3D CFD solver through geometric multiscale boundaries and a closed-loop 0D circulation. It demonstrates the crucial role of a biophysically detailed activation model (RDQ20) and a careful calibration process to achieve physiologic flow rates and biomarkers, validated against clinical data. The framework employs a RIIS-based valve representation within an ALE Navier-Stokes formulation, VMS-LES turbulence modeling, and a segregated numerical scheme to efficiently solve the coupled EM-Fluid-Circulation system. The authors apply the model to a pathological case of Left Bundle Branch Block, predicting electrical delay, mechanical dyssynchrony, altered ejection fractions, and increased wall shear stress in the LV septum, thereby illustrating the intrinsic multiphysics coupling of cardiac function. This work represents a significant step toward fully integrated, patient-relevant digital twins of cardiac function by bridging 3D heart mechanics, intracardiac hemodynamics, valve dynamics, and systemic circulation in a single framework.

Abstract

We introduce a multiphysics and geometric multiscale computational model, suitable to describe the hemodynamics of the whole human heart, driven by a four-chamber electromechanical model. We first present a study on the calibration of the biophysically detailed RDQ20 activation model (Regazzoni et al., 2020) that is able to reproduce the physiological range of hemodynamic biomarkers. Then, we demonstrate that the ability of the force generation model to reproduce certain microscale mechanisms, such as the dependence of force on fiber shortening velocity, is crucial to capture the overall physiological mechanical and fluid dynamics macroscale behavior. This motivates the need for using multiscale models with high biophysical fidelity, even when the outputs of interest are relative to the macroscale. We show that the use of a high-fidelity electromechanical model, combined with a detailed calibration process, allows us to achieve remarkable biophysical fidelity in terms of both mechanical and hemodynamic quantities. Indeed, our electromechanical-driven CFD simulations - carried out on an anatomically accurate geometry of the whole heart - provide results that match the cardiac physiology both qualitatively (in terms of flow patterns) and quantitatively (when comparing in silico results with biomarkers acquired in vivo). We consider the pathological case of left bundle branch block, and we investigate the consequences that an electrical abnormality has on cardiac hemodynamics thanks to our multiphysics integrated model. The computational model that we propose can faithfully predict a delay and an increasing wall shear stress in the left ventricle in the pathological condition. The interaction of different physical processes in an integrated framework allows us to faithfully describe and model this pathology, by capturing and reproducing the intrinsic multiphysics nature of the human heart.

Figures (21)

• Figure 1: The whole-heart EM model: a) cardiac muscular fibers, (b) boundaries and impulse sites (yellow spheres with bold labels), (c) coupling with circulation and we highlight the three main regions of the EM model (atria, ventricles and non-conductive regions).
• Figure 2: The whole-heart fluid domain: (a) subdomains composing the whole heart; (b) boundary portions (the left and right part are separated for visualization purposes).
• Figure 3: The 3D-0D fluid dynamics model of the whole-heart coupled to the surrounding circulation.
• Figure 4: Graphical representation of the overall algorithm to simulate the whole-heart hemodynamics driven by the EM model.
• Figure 5: Tetrahedral meshes used in the computational model: a) mesh for the EM simulation, b) mesh for the CFD simulation, c) mesh refinement on the valves region of the CFD mesh.