Regional assessment of left ventricular torsion by CMR tagging

Torsion between base and apex, base and mid, and mid and apex levels was calculated using CSPAMM tagging and Harmonic Phase tracking. The accuracy of torsion analysis on a regional basis (circumferential segments and transmural layers) was analyzed using an analytical model of a deforming cylinder with a displaced axis of rotation (AoR). Regional peak torsion values from twelve healthy volunteers calculated by the described method were compared to literature.The deviation from the analytical torsion per % AoR-displacement (of the radius) was 0.90 ± 0.44% for the circumferential segments and only 0.05% for the transmural layers. In the subjects, circumferentially, anterolateral torsion was larger than inferior (12.4 ± 3.9° vs. 5.0 ± 3.3°, N.S.). Transmurally, endocardial torsion was smaller than epicardial (7.5 ± 1.3° vs. 8.0 ± 1.5°, p < 0.001).Variability in the position of the AoR causes a large variability in torsion in circumferential segments. This effect was negligible for global torsion, and torsion calculated in transmural layers. Results were documented for the healthy human heart and are in agreement with data from literature.Torsion is the wringing motion induced by contracting myofibers in the left ventricular (LV) wall, in order to eject blood from the ventricle. The subsequent fast untwisting during early diastole is a major indicator of the restoring forces that contribute to rapid filling, since the blood is actively sucked from the left atrium [1] into the LV.Subendo- and subepicardial myofibers are obliquely oriented in opposite directions, with a smooth, transmural transition between the fiber directions [2]. Since torsion is directly related to myofiber orientation, structure, and function, it is an important indicator for the condition of the heart. Torsion was found to be a sensitive marker for both systolic and diastolic dysfunction [3-10]. This may allow for an early differentiation between diseased and normal myocardium, and discrimination be