Fibre Orientation in Human Fetal Heart and Ventricular Mechanics : A Small Perturbation Analysis

The study of the topological organisation of myocardial cells is a basic requirement for understanding the mechanical design of the normal and pathological heart. Anatomical observations show that cardiac muscle tissue has a highly specialized architecture. We have made new quantitative measurements of fibre orientation through the heart wall by means of polarized light analysis on some thick sections of human fetal heart embedded in a resin and polymerized. A small perturbation method to find an equilibrium solution in a cylindrical left ventricular (LV) geometry with fibres running on toroidal shells of revolution is used to investigate the mechanical behaviour of three human fetal hearts (FH) of 14, 20 and 33 weeks of gestational age. The results of fibre strains and stresses presented for end-systolic state show significant differences when compared to results of the cylindrical geometry with regular helicoidal fibres running on cylindrical surfaces. Moreover, the toroidal shells of revolution explain shear stresses and strains in the transverse plane which also exist in the adult heart.