[Paper Review] A comprehensive and biophysically detailed computational model of the whole human heart electromechanics

Marco Fedele, Roberto Piersanti+7 more|arXiv (Cornell University)|Jul 25, 2022

Cardiovascular Function and Risk Factors10 citations

TL;DR

This paper presents a biophysically detailed, whole-heart electromechanical model that integrates atrial and ventricular contraction with a closed-loop circulatory system, using advanced numerical schemes and feedback mechanisms to achieve unprecedented physiological accuracy in pressure-volume loops, deformation, and hemodynamics. The model sets a new benchmark for cardiac digital twins by incorporating multiscale physics and stable, high-fidelity simulations.

ABSTRACT

While ventricular electromechanics is extensively studied, four-chamber heart models have only been addressed recently; most of these works however neglect atrial contraction. Indeed, as atria are characterized by a complex physiology influenced by the ventricular function, developing computational models able to capture the physiological atrial function and atrioventricular interaction is very challenging. In this paper, we propose a biophysically detailed electromechanical model of the whole human heart that considers both atrial and ventricular contraction. Our model includes: i) an anatomically accurate whole-heart geometry; ii) a comprehensive myocardial fiber architecture; iii) a biophysically detailed microscale model for the active force generation; iv) a 0D closed-loop model of the circulatory system; v) the fundamental interactions among the different core models; vi) specific constitutive laws and model parameters for each cardiac region. Concerning the numerical discretization, we propose an efficient segregated-intergrid-staggered scheme and we employ recently developed stabilization techniques that are crucial to obtain a stable formulation in a four-chamber scenario. We are able to reproduce the healthy cardiac function for all the heart chambers, in terms of pressure-volume loops, time evolution of pressures, volumes and fluxes, and three-dimensional cardiac deformation, with unprecedented matching (to the best of our knowledge) with the expected physiology. We also show the importance of considering atrial contraction, fibers-stretch-rate feedback and suitable stabilization techniques, by comparing the results obtained with and without these features in the model. The proposed model represents the state-of-the-art electromechanical model of the iHEART ERC project and is a fundamental step toward the building of physics-based digital twins of the human heart.

Motivation & Objective

• To develop a comprehensive, biophysically detailed computational model of the entire human heart that captures both atrial and ventricular electromechanics.
• To address the challenge of modeling complex atrial anatomy and its physiological role in cardiac function, which is often neglected in prior models.
• To ensure numerical stability and accuracy in four-chamber simulations through advanced stabilization techniques and a segregated-intergrid-staggered scheme.
• To enable high-fidelity simulation of the cardiac cycle with realistic pressure-volume loops, deformation, and hemodynamic fluxes.
• To establish a foundation for physics-based digital twins of the human heart through integrated multiscale and multiphysics modeling.

Proposed method

• The model employs an anatomically accurate whole-heart geometry derived from medical imaging, with region-specific constitutive laws for atria, ventricles, and non-conductive structures.
• It incorporates a biophysically detailed microscale model for active force generation, including transmembrane potential dynamics and calcium-driven contraction.
• A 0D closed-loop circulatory system model is fully coupled with the mechanical model, enabling realistic hemodynamic feedback.
• The formulation includes key feedback mechanisms such as mechano-electric feedback and fiber-stretch/stretch-rate feedback to improve physiological realism.
• A novel segregated-intergrid-staggered finite element scheme is used, with stabilization techniques for circulation and fiber-stretch-rate feedback to ensure numerical stability.
• The model uses high-order time integration (BDF1/BDF2) and preconditioned iterative solvers (GMRES/CG with AMG) for efficient solution of large-scale nonlinear systems.

Experimental results

Research questions

• RQ1 Can a fully coupled, biophysically detailed electromechanical model of the whole human heart reproduce healthy physiological pressure-volume loops and deformation patterns with high accuracy?
• RQ2 What is the impact of including atrial contraction on hemodynamic performance and ventricular filling dynamics in a whole-heart simulation?
• RQ3 How do fiber-stretch-rate feedback and numerical stabilization techniques influence the stability and physiological fidelity of four-chamber cardiac simulations?
• RQ4 To what extent does the inclusion of region-specific material properties and anatomical complexity improve the model's physiological plausibility?
• RQ5 Can a unified, multiscale, and multiphysics model achieve stable and accurate simulation of the entire cardiac cycle across all chambers?

Key findings

• The model reproduces healthy cardiac function with unprecedented agreement to physiological benchmarks, including eight-shaped pressure-volume loops in the atria.
• The inclusion of atrial contraction significantly improves the accuracy of ventricular filling and stroke volume, with end-diastolic volume matching clinical expectations.
• Fiber-stretch-rate feedback is essential to prevent unphysiologically large blood fluxes, which otherwise lead to hemodynamic instability.
• The proposed stabilized numerical scheme enables stable simulation of the full cardiac cycle in a four-chamber setting, a major challenge in prior models.
• The model achieves high-fidelity reproduction of time-varying pressures, volumes, and 3D deformation across all chambers, with quantitative agreement to known physiological values.
• The use of region-specific parameters and constitutive laws results in realistic mechanical behavior across the left and right atria, ventricles, and valves.