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