Reference ranges for the various components of left ventricular myocardial deformation assessed by 3D speckle-tracking, and comparison with 2D speckle-tracking

Background: Speckle-tracking echocardiography (STE) enables the study of myocardial deformation and thus can provide insights about heart structure and function. However, 2D STE suffers from errors due to through-plane decorrelation. 3D STE overcomes such limitation, yet data regarding normality ranges for this new technology are lacking. Accordingly, we sought to assess the reference values of a newly developed 3D speckle-tracking method for longitudinal (L1), circumferential (C1), area (A1) and radial strain (R1), and then to compare them with those obtained by 2D STE. Methods: We acquired 3D full-volume data sets (32+2 vps) from apical approach in 78 healthy volunteers (37+11 years, 40 women) using Vivid E9 equipped with 4V probe (GE Healthcare, Horten, N) to measure the different components of LV deformation in 17 segments. 2D L1 was assessed in apical 4-, 3-, and 2-chamber views (76+6 fps) and C1 was measured in parasternal short-axis views (73+7 fps) during the same echo study. Results: Total study time was shorter with 3D than with 2D STE (5.1+1.1 vs 7.0+1.2 minutes; p, 0.001), due to shorter acquisition time (2+0.6 vs 4+2 minutes; p,0.001). Conversely, analysis time was similar for 3D and 2D STE (3.3+0.8 vs 3.0+0.8 minutes; p=NS). 3D L1 (-20%, 95%CI -19 to -21%) was significantly lower than 2D L1 (-21%, 95%CI -21 to -22%, p=0.0001). Global 3D C1 (-19%, 95%CI -19 to -20%) was higher than 2D C1 at basal level (-18%, 95%CI -17 to -19%, p=0.002), lower than 2D C1 at apical level (-30%, 95%CI -29 to -34%, p,0.0001), but similar to 2D C1 at mid-papillary level (-19%, 95%CI -17 to -21%, p=NS). 3D values for A1 and R1 were (-35%, 95%CI -36 to -34%, and 57%, 95%CI 55 to 59%, respectively). Reproducibility for the 3D strain components assessed in 20 subjects and expressed as mean difference of repeated measurements was: 0.5% and 1.5% for L1, 0.5 and 1.4% for C1, 0.6 and 2.1% for A1, 1.4 and 3.1% for R1, for intra- and inter-observer reproducibility, respectively. Conclusions: 3D STE is a simple, fast and reproducible technique for assessing the different components of LV myocardial deformation. Due to the reported inconsistency of LV strain values among different vendors, it is pivotal to establish vendor-specific reference values for this newly developed echo tehnique.