Apical four-chamber, short-axis grayscale, and color Doppler tissue images were prospectively acquired using Vivid 7 and iE33 ultrasound systems in 34 children and then analyzed using EchoPAC and QLAB (STE) and SPEQLE (CDTI).
Measurement of myocardial deformation was feasible for all three modalities. Longitudinal strain (¦Å) measurements showed the lowest intraobserver and interobserver variability (intraobserver and interobserver coefficients of variation, 9 % and 8 % for EchoPAC, 5 % and 6 % for QLAB, and 14 % and 16 % for SPEQLE). In addition, longitudinal ¦Å had a small bias and narrow limits of agreement when comparing different techniques. The coefficients of variation of circumferential ¦Å by EchoPAC and QLAB were 12 % and 11 % (intraobserver) and 9 % and 13 % (interobserver), respectively. Circumferential ¦Å by STE had a small systematic bias but relatively narrow limits of agreement. The reproducibility of radial ¦Å measurements using STE was low, while CDTI ¦Å provided better performance (intraobserver and interobserver coefficients of variation for radial posterior ¦Å, 12 % and 24 % for EchoPAC, 39 % and 56 % for QLAB, and 12 % and 14 % for SPEQLE). Radial ¦Å was on average 50 % lower using QLAB compared with EchoPAC and SPEQLE. Systolic strain rate values obtained by STE were lower compared with CDTI-derived values. The limits of agreement for strain rate values among the three modalities were wide, and intraobserver and interobserver variability was poor for all three modalities.
Some deformation measurements (e.g., longitudinal and circumferential ¦Å) are comparable among different ultrasound machines and software packages, whereas others are significantly different (e.g., radial ¦Å and strain rate). This study stresses the need for an industry standard for these techniques.