Finite Element Modeling of Cardiac Tissue Megan McCain ES240 - Solid Mechanics Final Project December 12, 2006
Cardiac Tissue Structure cell_structure2.jpg Cardiac cells (myocytes) are cylindrically shaped Mechanically attached end to end by intercalated disks –Site of electrical communication 50 µm Human Ventricle
Motivation Stretching isotropic monolayers of cardiac tissue shows a remodeling of gap junctions Relate stresses to changes in protein expression Zhuang J, KA Yamada, JE Saffitz, AG Kleber. Pulsatile Stretch Remodels Cell-to-Cell Communication in Cultures Myocytes. Circulation Research. 2000;87:316.
Model of Tissue Structure 100 µm x 20 µm myocytes separated by 2.5 µm x 20 µm gap junctions E myocytes = 35 kPa (literature) E intercalated disk = 60 kPa (guess) = 0.5 (literature) 100 µm 20 µm ABAQUS Lieber SC, et al. Aging Increases Stiffness of Cardiac Myocytes Measured by Atomic Force Microscopy Nanoindentation. Am J Physiol Heart Circ Physiol 287: H645-H651,2004.
Horizontal Stretch Load Surface Traction 5 kPa
Horizontal Stretch Stress
Horizontal Stretch Strain
Vertical Stretch Load
Vertical Stretch Stress
Vertical Stretch Strain
Comparing Stresses and Strains Gap junctions experience higher stresses Myocytes experience higher strains Stresses and strains higher during vertical stretch compared to horizontal stretch
Clinical Implications Myocardial infarctions (heart attacks) change the stresses on cardiac tissue Gap junctions and myocytes remodel in response to stress –Electrical remodeling can be arrhythmogenic