A microstructure-based finite element model of the human left ventricle for simulating the trans-scale myocardial mechanical behaviors

The hierarchical structure and heterogeneous composition of the myocardial tissue and the differential mechanical properties of myocardial components together make the mechanical behaviors of the left ventricle (LV) highly complex. In the present study, we developed a microstructure-based (MB) finite element model to quantify the time-varying myocardial mechanics of the LV during an entire cardiac cycle while accounting for the mechanical states of individual myocardial components. The modeling work started from building constitutive models for individual myocardial components based on their microstructure and mechanical properties, followed by combining them to form an integrated constitutive model of myocardial micro-tissue that was programmed on the discretized finite elements of the myocardium. Verification/validation studies performed at multiple scale levels demonstrated the good performances of the modeling methods. Numerical simulation for a normal LV reasonably reproduced the typical pressure-volume loop, demonstrated the spatiotemporal changes in myocardial displacement and stress over a cardiac cycle, and revealed the differential mechanical states of cardiomyocytes located in different myocardial regions. Furthermore, the model was applied to address the impact of regional replacement fibrosis. The results showed that replacement fibrosis impaired both the diastolic and the systolic functions, altered the spatial distributions of myocardial displacement and stress, and reduced the systolic cardiomyocyte stress in the fibrotic myocardial region. In summary, the study demonstrated the significance of accounting for the MB mechanical properties of myocardium when modeling the mechanical behaviors of the LV, and the model may contribute as a useful tool for addressing biomechanical problems related to cardiomyopathies.