Normal ranges of left atrial phasic strains and strain rates by 2D speckle-tracking echocardiography in pediatrics: a systematic review and meta-analysis

Establishing normal values of left atrial (LA) phasic strains and strain rates is essential for distinguishing between normal and abnormal functions, determining the degree of abnormality, and understanding the clinical significance of reported values in pediatrics. This meta-analysis aimed to establish normal values of two-dimensional speckle-tracking echocardiography (2DSTE)-derived LA phasic strains and strain rates in the pediatric population and identify the sources of inter-study heterogeneity for these values. A comprehensive search of PubMed, Scopus, and Embase databases was conducted using keywords such as "left atrial/left atrium," "strain/speckle/deformation," and "echocardiography" combined with pediatric age categories. Inclusion criteria comprised English-language human studies involving healthy subjects under 18 years of age. Subjects were categorized as neonates (up to 1 month), infants (1-12 months), and children (1-18 years). A random-effects model was applied to determine 2DSTE-derived LA strains and strain rates, and a meta-regression analysis was performed to investigate inter-study heterogeneity. Our analysis included 17 studies involving 1448 healthy subjects. For children, the mean values of LA strains during the reservoir, conduit, and contraction phases were 47.3% (95% CI 42.5-52.1%), 32.8% (95% CI 27.8-37.8%), and 12% (95% CI 10.0-14.1%), respectively. The mean values for LA strain rates were 2.4 s-1 (95% CI 1.1-3.8 s-1), 4.3 s-1 (95% CI 0.6-8.0 s-1), and 2.4 s-1 (95% CI 0.4-4.5 s-1), respectively. Inter-study heterogeneity for 2DSTE-derived LA phasic strains and strain rates was attributed to factors such as the number of study participants, publication year, software utilized, gating methods, the number of analyzed segments, the geographical region of the study, and heart rate. This study established the normal range of 2DSTE-derived LA phasic strains and strain rates. Additionally, inter-study heterogeneity was found to be influenced by various demographic, physiologic, and methodological factors.