Abstract:
This study undertakes a detailed finite element (FE) analysis to determine the stress state and deformation of the human left ventricle when subjected to high positive Gz (+Gz) accelerations, such as those experienced by fighter pilots. Motivated by reports of cardiac tissue damage in animals under these conditions, the research aims to provide a computational estimate of the mechanical response of the heart. A 3D FE model of the left ventricle, consisting of 3,830 solid elements with three layers through the wall thickness, was generated from anatomical surface data.
Using the MARC finite element program, a quasi-static analysis was performed for the diastolic phase of the ventricle under various acceleration levels. The analysis accounted for geometric nonlinearities by employing an updated Lagrangian method. For the initial analysis, the myocardium was modeled as an isotropic, nearly incompressible soft elastic material. The results demonstrated that under high +Gz loading, the left ventricle undergoes significant deformation, becoming longer while its diameter decreases. The computed stress distribution was highly non-uniform, with the greatest Von Mises stresses concentrated at the constrained base of the heart. The paper also provides a thorough theoretical review of more advanced constitutive models for future work, including treating the heart muscle as a blood-perfused porous medium with orthotropic, viscoelastic properties.
