Normal Reference Values and Determinants of Right Heart Strain Derived From MR-Feature Tracking: A Meta-Analysis.

A comprehensive assessment of normal reference values for right atrial (RA) and right ventricular (RV) strain derived from MR-feature tracking (MR-FT) is somewhat lacking. To systematically review and meta-analyze reference values of RV and RA strain parameters using MR-FT in healthy adults and to identify their principal determinants. Meta-analysis. A total of 4228 healthy adults from 40 studies (2322 male, age range: 18-79 years). 1.5 and 3.0 T/balanced steady-state free precession. A systematic search of PubMed, Embase, and Web of Science identified studies on right heart strain in healthy adults published before January 1, 2025, by two investigators. A random-effects model aggregated RV and RA strain parameters. Subgroup and meta-regression analyses assessed the effects of race, sex, age, FT software, MR vendor, and field strength. Random-effects model with pooled means and 95% confidence intervals, I2 statistic, and Egger's test. p < 0.05 was considered significant. The pooled means of RV global longitudinal, circumferential, and radial strain (RV-GLS, RV-GCS, and RV-GRS) were -22.57%, -14.16%, and 26.04%, respectively. The pooled RA reservoir, conduit, and booster strain (RA-εs, RA-εe, and RA-εa) were 47.01%, 28.24%, and 18.62%, respectively. Subgroup and meta-regression analyses identified race, sex, age, and FT software as contributing significantly to the variability in right heart measurements, while MR vendor (p = 0.437 for RV-GLS, 0.347 for RV-GCS, 0.240 for RV-GRS, 0.135 for RA-εs, 0.162 for RA-εe, and 0.287 for RA-εa) and field strength (p = 0.436 for RV-GLS, 0.041 for RV - GCS, 0.081 for RV-GRS, 0.926 for RA-εs, 0.377 for RA-εe, and 0.296 for RA-εa) had a limited impact. This study provided the pooled normal values of RV and RA strain parameters in healthy adults using MR-FT and highlighted the considerable impact of race, sex, age, and FT software on right heart strain measurements. Stage 5.