STE Image Acquisition and Analysis
For acquisition of 2D images for STE analysis, the machine was adjusted to acquire 3 cardiac cycles, with frame rate between 40-80 frames/s. Images were obtained in the parasternal short axis (PSAX) in its 3 main levels: basal (mitral valve), mid (papillary muscles) and apical. LV apical window was composed by: longitudinal (APLAX), four (A4C) and two chambers (A2C) views.
Off-line analyses were performed using the software EchoPAC, version v20.1 (GE Medical Systems, Milwaukee, WI, USA). The parameters evaluated were: strain (ε,%) and strain rate (ε’,s-1); maximum basal and apical rotations (VErot,o) and their peak absolute rotational velocities (VErot-v,o/s), LV twist (VEtw,o) and torsion (VEtor,o/cm), and their velocities (VEtw-v,o/s; VEtor-v,o/s.cm). LV twist was calculated as the net absolute difference between maximum apical and basal systolic peak rotations (VEtw = apical VErot - basal VErot) and torsion as the twist normalized to LV longitudinal length. By convention, baseline rotation values ​​were negative, and apical, positive (figure 1).21