Cardiac magnetic resonance imaging derived reference values for ventricular anatomy and function and myocardial tissue characterization in adolescents: the EnIGMA study
Authors: Real C , Parraga R , Gonzalez-Calvo E , Pizarro G , Garcia-Lunar I , Sanchez-Gonzalez J , Sampedro P , Roda-Sanmamed I , Martinez-Gomez J , De Miguel M , De Cos-Gandoy A , Bodega P , Santos-Beneit G , Fuster V , Fernandez-Jimenez R 
Published: October 2022

Abstract

Introduction
Cardiac magnetic resonance (CMR) imaging is a precise tool for the assessment of cardiac anatomy and function. However, studies providing reference values for CMR parameters, including myocardial tissue properties, in healthy adolescents are scarce.

Purpose
To provide CMR derived reference values for biventricular mass, volumes and function measured by cine steady-state free-precession (SSFP) sequences and myocardial tissue relaxation properties as measured by native T1- and T2-mapping sequences in healthy adolescents.

Methods
A comprehensive non-contrast CMR study was performed in healthy adolescents aged 15 to 18 years enrolled in the “Early ImaginG Markers of unhealthy lifestyles in Adolescents” (EnIGMA) project using a 3-Tesla CMR scanner between March 2021 and October 2021. The imaging protocol included a cine SSFP to provide high-quality images for chamber size and function analysis, and a T2-GraSE mapping and native T1-mapping sequences (MOLLI Scheme 5 (3) 3) to provide precise myocardial relaxation time properties. Images were analyzed by experienced observers using the Cardiac Analysis tool available at IntelliSpace Portal following a standard protocol. In cine SSFP sequences, right and left ventricles were manually contoured for end-diastolic and end-systolic phases in the short-axis orientation, respectively (Figure 1A, B). Native T1 and T2 maps were analyzed in a mid-ventricular short axis slice and summarized values per individual were determined (Figure 1C, D). Student's t-tests were used for between-gender comparisons.

Results
CMR scans were performed in 123 adolescents (63 girls, 51.2%) with a mean age of 16.0 years (standard deviation (SD)=0.5), mean body mass index of 21.4 (SD=3.2) kg/m2, mean body surface area of 1.69 (SD=0.16) m2, and mean heart rate during CMR acquisitions of 69 (SD=11) beats/minute. Reference percentiles (P) 3, 10, 25, 50, 75, 90 and 97 for the different parameters analyzed by gender are provided in Figure 2. Mean left and right ventricular end-diastolic indexed volumes were higher in boys than in girls (91.5 vs 78.1 ml/m2, p&lt;0.01; and 101.1 vs 84.2 ml/m2, p&lt;0.01), as well as the indexed cardiac mass (48.4 vs 36.4 g/m2, p&lt;0.01). Left ventricular ejection fraction (LVEF) was similar in boys and girls (62.0 vs. 62.9%, p=0.23), whereas right ventricular ejection fraction was slightly lower in boys than in girls (55.3 vs. 57.1%, p=0.03). Mean myocardial native T1 relaxation time was 1253 (SD=28) ms in girls and 1215 (SD=23) ms in boys (p&lt;0.01), whereas mean myocardial T2 relaxation time was 44.1 (SD=2.3) ms and 44.4 (SD=2.0) ms in girls and boys, respectively (p=0.46).

Conclusion
This study provided CMR derived reference values for biventricular anatomy, function, and myocardial tissue properties, in healthy adolescents aged 15 to 18 years. This information may be useful for the differential diagnosis of cardiac diseases, such as cardiomyopathies and myocarditis, in adolescent population.

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