Comparison of 2D and 3D calculation of left ventricular torsion as circumferential-longitudinal shear angle using cardiovascular magnetic resonance tagging

CMR tagging was performed in six healthy volunteers. From this, LV torsion was calculated using a 2D and a 3D method. The cross-correlation between both methods was evaluated and comparisons were made using Bland-Altman analysis.The cross-correlation between the curves was r2 = 0.97 ± 0.02. No significant time-delay was observed between the curves. Bland-Altman analysis revealed a significant positive linear relationship between the difference and the average value of both analysis methods, with the 2D results showing larger values than the 3D. The difference between both methods can be explained by the definition of the 2D method.LV torsion represented as CL shear quantified by the 2D and 3D analysis methods are strongly related. Therefore, it is suggested to use the faster 2D method for torsion calculation.Left ventricular (LV) torsion is a sensitive marker for both systolic and diastolic dysfunction [1-3], and is therefore a useful addition to other strain measures such as radial, circumferential and longitudinal strain. LV torsion can be assessed using several techniques like speckle tracking echocardiography [4,5] and cardiovascular magnetic resonance (CMR) myocardial tagging [6,7]. However, there is still a debate on how to describe and calculate torsion in an optimal way, as a gold standard is not yet available. A straightforward determination method for LV torsion will facilitate clinical use of this measure.Several methods to describe LV torsion have been previously published. First, the twist angle is used [8]. In this approach, the basal and apical rotations of the ventricle are subtracted, giving an indication of its twist. A second method is to divide this angle by the length of the ventricle, which describes a LV twist per unit length [9]. This parameter has the advantage of allowing the comparison of torsion between hearts of different sizes. A third method is to also take the radius of the heart into account. This describes torsion as the circumferen