MRI tagging is a powerful new method for non-invasively studying LV wall deformation. The counterclockwise spiral of epicardial fibers coupled with the clockwise spiral of endocardial fibers, provides a mechanism for extensive thickening. Epicardial deformation is in the direction of its fibers. Endocardium is forced to shorten mostly in the cross-fiber direction, a deformation that results in extensive thickening. Systolic torsion recoils rapidly before diastolic filling begins, likely representing release of restoring forces and augmenting filling. This recoil is diminished in LVH.