Echocardiography Data Acquisition.
Transthoracic echocardiography was performed with a commercially
available ultrasonography system (iE33, Philips Medical Systems, Andover
Massachusetts) equipped with S5-1(1 to 5 MHz) and X3-1 (1 to 3 MHz).
Standard three-dimensional (3D) images were acquired according to the
recommendations of the American Society of Echocardiography. Six cardiac
consecutive cycles for 3DE images were acquired for offline analysis. A
wide sector was used to ensure that the entire LV cavity was included
within the full-volume data set. Image parameters such as depth, sector
size, angle, and focus were optimized to achieve a frame rate range of
60 to 80 fps for 2DE and 30 to 45 fps for 3DE analysis.
Offline analysis of the left and right ventricular three-dimensional
(3D) image data was performed using the TomTec 4D RV analysis
workstation (version 4.6.0.411, TomTec Imaging Systems,
Unterschleißheim, Germany)[19]. Care was taken to include trabeculae
during measurements. The endocardial borders were traced from the three
apical views by an observer blinded to the clinical outcome. GLS and the
average peak LV longitudinal systolic strain from the three apical
windows were measured. GLS was calculated by measuring the entire
endocardial line length at the end-diastole and end-systole (L1- L0/L0*
100%) in each view and averaging the results from the three views. RV
end-diastolic volume (RVEDV); RV end-systolic volume (RVESV); RV
ejection fraction (RVEF); LV end-diastolic volume (LVEDV); end-systolic
volume (LVESV); and LVEF were measured. RV longitudinal free wall strain
(RVLFS); RV longitudinal septal strain (RVLSS); LV global longitudinal
strain (LVGLS); and LV global circumferential strain (LVGCS) were
acquired simultaneously (Supplemental Figure 1). The intra-observer and
interobserver variability values were calculated as the absolute
differences between the corresponding 2 measurements in percentages of
their mean and intraclass correlation.