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.