Heart Mechanical Model Based on Holzapfel Experiments Milos Kojic 1,2,3(B ) , Miljan Milosevic 2,4 , Bogdan Milicevic 2,5 , and Vladimir Simic 2,5 1 The Department of Nanomedicine, Houston Methodist Research Institute, 6670 Bertner Avenue, R7 117, Houston, TX 77030, USA mkojic42@gmail.com 2 Bioengineering Research and Development Center BioIRC Kragujevac, Prvoslava Stojanovica 6, 34000 Kragujevac, Serbia 3 Serbian Academy of Sciences and Arts, Knez Mihailova 35, 11000 Belgrade, Serbia 4 Belgrade Metropolitan University, Tadeusa Koscuska 63, 11000 Belgrade, Serbia 5 Faculty for Engineering Sciences, University of Kragujevac, Sestre Janic 6, 34000 Kragujevac, Serbia Abstract. We have formulated orthotropic material model for human heart tissue based on experimental investigation of passive material properties of myocardium [1]. The Cauchy stress/stretch and shear stress/amount of shear relation curves are used, which are established experimentally under different loading conditions: biaxial extension and triaxial shear. The averaged curves obtained from all consid- ered specimens in [1] are reconstructed and used in our FE computational model. A computational procedure for determination of stresses for current stretches and amounts of shear at integration points of the FE model is implemented in the code PAK. Compressibility condition is imposed to couple the normal stresses using a penalty formulation. Applicability and reliability of this material model is tested on simple 3D models and on a heart wall segment under passive conditions. This numerical model offers an accurate description of the ventricular mechanics and can be used in studying heart problems in order to improve medical treatment of heart diseases. Keywords: Heart mechanics · Heart material model · Biaxial loading · Sommer and Holzapfel experiment 1 Introduction Cardiovascular diseases (CVDs) remain the leading cause of death in the developed world, accounting for an estimate of 17.3 million every year. The treatment of heart diseases by established therapies could only in part improve the outcome, but novel therapies need to be developed to affect the disease process more fundamentally. The application of ICT (Information and Communication Technologies), especially biome- chanical simulations, in solving the problems of heart diseases and improving therapies, has been recognized as important activity in the health care sector. Nowadays, there are models and supercomputers capable of simulating complex physiological events. © Springer Nature Switzerland AG 2020 N. Filipovic (Ed.): ICCB 2019, LAIS 11, pp. 12–21, 2020. https://doi.org/10.1007/978-3-030-43658-2_2