Cardiovascular magnetic resonance derived biventricular strain in healthy adolescents: reference values and comparison between myocardial tagging and feature-tracking
Authors: Real C , Parraga R , Gutierrez E , Gonzalez-Calvo E , Diaz-Munoz R , Sanchez-Gonzalez J , Pizarro G , Garcia-Lunar I , Martinez-Gomez J , Fernandez-Jimenez R 
Published: May 2023

Abstract

Funding Acknowledgements
Type of funding sources: Public grant(s) – EU funding. Main funding source(s): Instituto de Salud Carlos III (ISCIII) European Regional Development Fun/European Social Fund (A way to make Europe/Investing in your future).

Background
Strain measurements have demonstrated to be earlier and more sensitive markers of contractile dysfunction than ejection fraction (EF) alone. Myocardial tagging (MT) is considered the reference standard for CMR strain measurements, but its clinical application is limited because acquisition and analysis are laborious and time consuming. Feature-tracking (FT) CMR allows strain quantification using steady-state in free-precession (SSFP) sequence, which is obtained in routine CMR protocols, being easily applicable in clinical practice. Literature regarding reference strain values in pediatric populations is scarce and, to the best of our knowledge, there are no studies comparing FT and MT in healthy adolescents.

Purpose
To provide CMR strain reference values in healthy adolescents and compare FT to MT results.

Methods
A CMR study was performed in healthy adolescents enrolled in the "Early ImaginG Markers of unhealthy lifestyles in Adolescents" (EnIGMA) project using a 3-Tesla CMR scanner between March and October 2021. The imaging protocol included a cine SSFP to provide images for chamber size and function, including FT; and MT acquisitions using spatial modulation of magnetization (SPAMM) technique. Cine acquisitions included the entire left ventricular (LV) short axis and long-axis 4 chamber (4c)- and 2 chamber (2c)-views, while MT acquisitions included three short axis slices (basal, mid and apical) and long-axis 4c-view. Endo- and epicardial borders were manually contoured in the end-diastolic (ED) phase. A non-rigid, elastic algorithm was used for segmentation and registration for strain quantification. If tracking was suboptimal, the software only allowed adaptations of the contours on the ED image. Longitudinal (LS) and circumferential (CS) strains were obtained for the LV and right ventricle (RV).

Results
CMR scans were performed in 123 adolescents (64 girls, 52.0%) with a mean age of 16.0 years (standard deviation [SD]=0.4), a mean LVEF of 62.5% (SD=4.1) and a mean RVEF of 56.2% (SD=4.6). Reference percentiles (P) 3, 10, 25, 50, 90 and 97 for strain values by sex are provided in Figure 1. FT-measured LVLS and LVCS were higher in girls than in boys (-19.8 vs -17.8%, p&lt;0.01; and -22.2 vs -21.0%, p&lt;0.01; respectively), and these differences were confirmed with MT analysis. There were no consistent between-sex differences for RVLS and RVCS. Bland-Altman analyses showed reasonable agreement between FT and MT for LVLS, LVCS, RVLS and RVCS (Figure 2 A, B, C and D).

Conclusions
This study provided CMR derived reference values for left and right ventricle strain in adolescents aged 15 to 18 years. This work suggests that FT is a reasonably valid technique to measure LV and RV strain in this population. This information may be useful for diagnostic and prognostic implications in adolescent patients.