Normal Ranges of Left Atrial Strain by Speckle-Tracking Echocardiography: A Systematic Review and Meta-Analysis

Background Recent advances in the assessment of myocardial function have facilitated the direct measurement of atrial function using speckle-tracking echocardiography. Currently, normal reference ranges for atrial function using speckle-tracking echocardiography are based on a few initial studies, with variations among modestly sized (n = 100–350) studies. Methods The authors searched the PubMed, Embase, and Scopus databases for the key terms “left atrial/atrial/atrium” and “strain/function/deformation/stiffness” and “speckle tracking/Velocity Vector Imaging/edge tracking.” Studies of global left atrial function using speckle-tracking were selected if they involved >30 normal or healthy participants without any cardiac risk factors. Normal ranges for reservoir strain, conduit strain, and contractile strain were computed using a random-effects model. Meta-regression and subgroup analysis was performed to explore between-study heterogeneity. Results Forty studies (2,542 healthy subjects) satisfied the inclusion criteria. Meta-analysis revealed a normal reference range for reservoir strain of 39% (95% CI, 38%–41%, from 40 articles), for conduit strain of 23% (95% CI, 21%–25%, from 14 articles), and for contractile strain of 17% (95% CI, 16%–19%, from 18 articles). Meta-regression identified heart rate (P = .02) and body surface area (P = .003) as contributors to this heterogeneity. Subgroup analyses revealed heterogeneity due to sample size (n > 100 vs N < 100, P = .02). Conclusions The normal reference ranges for the three components of left atrial function are demonstrated. The between-study heterogeneity is explained partly by heart rate, body surface area, and sample size. Recent advances in the assessment of myocardial function have facilitated the direct measurement of atrial function using speckle-tracking echocardiography. Currently, normal reference ranges for atrial function using speckle-tracking echocardiography are based on a few initial studies, with variations among modestly sized (n = 100–350) studies. The authors searched the PubMed, Embase, and Scopus databases for the key terms “left atrial/atrial/atrium” and “strain/function/deformation/stiffness” and “speckle tracking/Velocity Vector Imaging/edge tracking.” Studies of global left atrial function using speckle-tracking were selected if they involved >30 normal or healthy participants without any cardiac risk factors. Normal ranges for reservoir strain, conduit strain, and contractile strain were computed using a random-effects model. Meta-regression and subgroup analysis was performed to explore between-study heterogeneity. Forty studies (2,542 healthy subjects) satisfied the inclusion criteria. Meta-analysis revealed a normal reference range for reservoir strain of 39% (95% CI, 38%–41%, from 40 articles), for conduit strain of 23% (95% CI, 21%–25%, from 14 articles), and for contractile strain of 17% (95% CI, 16%–19%, from 18 articles). Meta-regression identified heart rate (P = .02) and body surface area (P = .003) as contributors to this heterogeneity. Subgroup analyses revealed heterogeneity due to sample size (n > 100 vs N < 100, P = .02). The normal reference ranges for the three components of left atrial function are demonstrated. The between-study heterogeneity is explained partly by heart rate, body surface area, and sample size.