Non Invasive Estimation of Left VentrNon Invasive Estimation of Left Ventricular Normalized Torsion Angle in Healthy Persons by Echo Tracking Algorithm: Short Axis Viewicular Normalized Torsion Angle in Healthy Persons by Echo Tracking Algorithm: Short Axis View

Background: Left ventricular (LV) torsion angle is a key parameter of cardiac performance but is difficult to measure. The purpose of this study is to describe a noninvasive imaging method for the assessment of these complex cardiac motions.

Objectives: In this study, left ventricular torsion angle and normalized torsion angle were estimated in the short axis view for healthy persons.

Patients and Methods: We acquired basal and apical short axis left ventricular LV images in the short axis view for 14 healthy men to estimate LV torsion angle by echo tracking under a block-matching (BM) algorithm. By extracting the instantaneous changes in total displacement vector in the short axis view throughout a cardiac cycle, we calculated the instantaneous rotation and torsion angles in the short axis view. To account for differences in heart size, normalized torsion was calculated based on the radius of both the apical and basal slices in the end diastolic frame.

Results: Apical and basal rotation was measured from short axis images by automatic frame-to-frame tracking of grayscale echo patterns. The vertical and horizontal displacements of the apical level were more than those of the basal level. All data are expressed as mean ± standard deviation (SD). Data was tested for normal distribution and homogeneity of variance by the Kolmogorov-Smirnov test (K-S) and Levene’s test respectively.
The peak rotation angles of the basal and apical levels and LV torsion angle in the short axis view were 8.0 ± 1.6°, 9.5 ± 1.8°, and 17.3 ± 2.5°, respectively. The normalized torsion was calculated as 7.8 ± 1.3°, based on the basal maximum radius, the apical maximum radius, and the distance between the apical and basal levels.

Conclusions: We conclude that the normalized torsion angle is an important biomechanical parameter, because it is independent of heart size and distorted geometries in pathological ventricles.