Normal Ranges of Right Atrial Strain

Standard measures for the clinical assessment of right atrial (RA) function are lacking. In this systematic review and meta-analysis, the authors sought to report a reference range for RA deformation parameters in healthy subjects and to identify factors that contribute to reported variations. The authors conducted a comprehensive search of MEDLINE; MEDLINE In-Process & Other Non-Indexed Citations; Embase; Scopus; and the Cochrane Central Register of Controlled Trials from database inception through October 2021. Studies were included if they reported RA strain or strain rate (SR) using 2-dimensional speckle-tracking echocardiography in healthy volunteers or apparently healthy control patients. Data were extracted by 1 reviewer and then reviewed by 2 independent reviewers. Conflicts were resolved through consensus. Data were combined using the method developed by Siegel and adjusted using the restricted maximum likelihood random-effects model. The normal range was defined as the 95% CI of the mean. Heterogeneity was assessed by the Cochran Q-statistic and the inconsistency index (I2). The quality of the included studies and publication bias were assessed. Effects of clinical variables were sought in a metaregression. The search identified 4,111 subjects from 21 studies. The average RA reservoir strain was 44% (95% CI: 25%-63%), contractile strain was 17% (95% CI: 2%-32%), and conduit strain was 18% (95% CI: 7%-28%), with significant between-study heterogeneity and inconsistency. The systolic SR was 2.1 s-1 (95% CI: 0.9-3.4 s-1), early-diastolic SR was −2.0 s-1 (95% CI: −3.3 to −0.8 s-1), and late-diastolic SR was −1.9 s-1 (95% CI: −2.4 to −1.3 s-1), with nonsignificant heterogeneity and inconsistency. Ranges remained wide in healthy volunteers. The metaregression identified only age as significantly associated with systolic SR and no other significant determinants of variation among normal ranges of strain. There are wide reference ranges for RA deformation, and these may limit the utility of this test in clinical practice.