Echocardiography
Transthoracic echocardiography was performed using commercially available General Electric systems (VIVID Q, S6 or Vivid 7, GE Vingmed Ultrasound AS, Horten, Norway). Apical long axis, 4-chamber and 2-chamber views were digitally recorded at a frame rate of >40 fps for offline 2DLS analysis. Standard echocardiographic findings, but not 2DLS findings, were available to the attending physician.
An echo study was performed within 24h of the patients’ last chest pain episode. Patients with suboptimal 2D echo image quality, defined as ≥2 technically suboptimal segments from apical views, were excluded from the study. All echocardiograms were analyzed in a core lab (Lady Davis Carmel Medical Center) by a single experienced sonographer (IA) blinded to all clinical data. Of the 700 patients initially enrolled in the 2DSPER study 48 (6.9%) did not meet the 2D echo image quality criteria and were withdrawn from the study after the initial core lab analysis. The final cohort included 605 patients who had complete clinical and echocardiographic data, including adequate 2DLS analysis. In all 605 patients included, tracking in all LV segments was feasible according to the 2DLS analysis software.
All 605 echocardiograms included in the final 2DSPER study cohort were reviewed by a second experienced sonographer (MG) blinded to all clinical and 2DLS data. Studies with the best image quality, defined as optimal visualization of all left ventricular segments throughout the cardiac cycle in all 3 apical views, were classified by the blinded sonographer as high quality, and the rest as low quality.22
All echocardiograms were analyzed using a dedicated 2DLS software (EchoPAC SW version 113.0.3; GE Vingmed Ultrasound AS). For each patient GLS was computed by averaging all 18 segments. Reproducibility of GLS measurements in the 2DSPER study has been previously reported.15