A NEW HYPERELASTIC MODEL FOR HUMAN MYOCARDIUM

article in a collection out of WoS and Scopus

en

Human myocardium is formed by locally parallel muscle fibres which are arranged in layers, sometimes called sheets [1]. This structure determines the orthotropic mechanical response of myocardium, as evidenced by the results of biaxial extension tests and simple shear tests [2]. A suitable hyperelastic model for myocardium should reflect its structure and produce an orthotropic response with highest stiffness in the fibre direction, f, intermediate in the sheet direction, s, and lowest in the sheet-normal direction, n (f, s and n are mutually orthogonal). The most widely used model which satisfies these requirements is that proposed by Holzapfel and Ogden [3]. It introduces two orthogonal families of fibres, one in the f direction and the other in the s direction. The families are represented by two exponential terms in the strain-energy density function, formulated in terms of invariants ������4f=������∙������������ and ������4s=������∙������������ which equal the square of stretch in f and s directions, respectively (������ is the right Cauchy-Green tensor). However, the family in the s direction is somewhat artificial since in myocardium there is no distinct family of fibres (collagen of others) arranged predominantly perpendicular to the muscle fibres; instead, the chains of myocytes are bundled by endomysial connective tissue with membraneous appearance [4]. For this reason, we present a modification of the model which reflects more accurately the laminar structure of myocardium and turns out to have better capability to reproduce experimental responses.

Human myocardium is formed by locally parallel muscle fibres which are arranged in layers, sometimes called sheets [1]. This structure determines the orthotropic mechanical response of myocardium, as evidenced by the results of biaxial extension tests and simple shear tests [2]. A suitable hyperelastic model for myocardium should reflect its structure and produce an orthotropic response with highest stiffness in the fibre direction, f, intermediate in the sheet direction, s, and lowest in the sheet-normal direction, n (f, s and n are mutually orthogonal). The most widely used model which satisfies these requirements is that proposed by Holzapfel and Ogden [3]. It introduces two orthogonal families of fibres, one in the f direction and the other in the s direction. The families are represented by two exponential terms in the strain-energy density function, formulated in terms of invariants ������4f=������∙������������ and ������4s=������∙������������ which equal the square of stretch in f and s directions, respectively (������ is the right Cauchy-Green tensor). However, the family in the s direction is somewhat artificial since in myocardium there is no distinct family of fibres (collagen of others) arranged predominantly perpendicular to the muscle fibres; instead, the chains of myocytes are bundled by endomysial connective tissue with membraneous appearance [4]. For this reason, we present a modification of the model which reflects more accurately the laminar structure of myocardium and turns out to have better capability to reproduce experimental responses.

myocardum; heart; hyperelastic model

09.07.2023

ESB

Maastricht

ESB 2023 BOOK OF ABSTRACTS

28

1