Background
The establishment of the range of reference values and associated variations of two-dimensional speckle-tracking echocardiography (2DSTE) derived left ventricular (LV) strain is a prerequisite for its routine clinical adoption in pediatrics. The aims were to perform a meta-analysis of normal ranges of LV global longitudinal, circumferential, and radial strain (GLS, GCS, and GRS) measurements derived by 2DSTE in children and identify confounding factors that may contribute to variances in reported measures.
Methods
A systematic review was launched in Medline, Embase, Scopus, CINAHL, and Cochrane. Search hedges were created to cover the concepts of pediatrics, speckle-tracking echocardiography, and left heart ventricle. Two investigators independently identified and included studies if they reported the 2DSTE derived LV GLS, GCS or GRS. The weighted mean was estimated by using random-effects with 95% confidence interval (CI), heterogeneity was assessed by the Cochran's Q statistic and the inconsistency index (I2) and publication was evaluated using the Egger test. Effects of demographic (age), clinical, and vendor variables were assessed in a meta-regression.
Results
The search identified 2325 children from 43 data sets. The reported normal mean values of GLS among the studies varied from -16.7% to -23.6% (mean -20.2%, 95% CI -19.5% to -20.8%), GCS varied from -12.9% to -31.4% (mean -22.3%, 95% CI -19.9% to -24.6%) and GRS, varied from 33.9% to 54.5 % (mean 45.2 95% CI 38.3 to 51.7). 26 studies reported LS only from the apical 4-chamber view with a mean of -20.4%, (95% CI -19.8% to -21.7%). 23 studies reported CS (mean, -20.3%, 95% CI -19.4% to -21.2%) and RS (mean, 46.7%, 95% CI 42.3% to 51.1%) from the short axis view at the mid-ventricular level. A significant apex-to-base segmental longitudinal strain (SLS) gradient (P < .01) was observed in the LV free wall. There was significant between- study heterogeneity and inconsistency (I2 > 94% and P < .001 for each strain measure), which was not explained by age, gender, body surface area, blood pressure, heart rate, frame rate, FR/HR ratio tissue-tracking methodology, location of reported strain value along the strain curve, ultrasound equipment, or software. These metaregression showed that these effects were not significant determinants of variations among normal ranges of strain values. There was no evidence of publication bias (P = .40).
Conclusions
This study defined reference values of 2DSTE derived LV strain in children on the basis of a meta-analysis. In healthy children, the mean LV global longitudinal strain value is -20.2%, (95% CI -19.5% to -20.8%), mean global circumferential strain -22.3%, (95% CI -19.9% to -24.6%), and mean global radial strain is 45.2%, (95% CI 38.3% to 51.7%). LV segmental longitudinal strain has a stable apex-to-base gradient that is preserved throughout maturations. Although variations among different reference ranges in this meta-analysis were not dependent on differences in demographic, clinical, or vendor para...