Derivation of myocardial fiber stiffness equation based on theory of laminated composite

The constitutive equation with stress-dependent coefficients for laminated composite is derived and employed for iterative determination of myocardial fiber's stiffness equation E_f = K_σf + C from myocardial strip's stiffness equation E_s = K_sσs + C_s. The strip's stiffness constants K_s and C_s are estimated by the leastsquare curve fitting of the stress-strain data experimentally obtained from uniaxially stretching of strips of left ventricular heart wall excised from seven canine hearts. The values of K and C computed at selected fiber orientations across the thickness of the strip and using three, five, and ten-layer approximations are reported.