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Figure 2 Myofiber Architecture of LV and Models for Understanding LV Twist Dynamics

Myofiber orientation in the left ventricular (LV) changes smoothly from a left-handed helix in the subepicardium to a right-handed helix in the subendocardium (A, left). Thick-walled cylindrical myofibers models proposed by Ingels et al. (A, right) and Taber et al. (B), showing the subendocardial fiber wrapped in a right-handed helix and a subepicardial fiber wrapped in a left-handed helix. Arrows (A) depict the circumferential components of force that results from force development in each fiber direction. The radii (R₁ for subendocardium and R₂ for the subepicardium) are the lever arms, which convert these circumferential components of force into torque about the long axis of the cylinder. The subepicardial fibers have a longer arm of moment than the subendocardial fibers (R₁< R₂). Figure illustration done by Rob Flewell.