Add to ORKGAbstract. Mathematical modeling of cardiac mechanics could be a use-ful clinical tool, both in translating measured abnormalities in cardiac deformation into the underlying pathology, and in selecting a proper treatment. We investigated to what extent a previously published model of cardiac mechanics [6] could predict deformation in the healthy left ventricle, as measured using MR tagging. The model adequately pre-dicts circumferential strain, but fails to accurately predict shear strain. However, the time course of shear strain proves to be that sensitive to myofiber orientation, that agreement between model predictions and ex-periment may be expected if fiber orientation is changed by only a few degrees.