Longitudinal left ventricular mass indexing for DEXA-measured lean mass and fat mass: novel normative reference centiles in postpubertal adolescents and young adults

Abstract

Current left ventricular mass cut points for pediatric left ventricular hypertrophy are inaccurate. The inaccuracies are due, in part, to the average age of participants (11.6 yr) evaluated and also due to the lack of Echo and DEXA-measured body composition in postpubertal youth. Novel sex-based cut points are proposed for postpubertal youths at 17 and 24 yr. The new 95th percentile cut points are 15–20 g/m ^2.7 higher than the current cut point.

Abstract

Left ventricular (LV) hypertrophy derived from LV mass (LVM) cut point is a marker of cardiovascular events in adults and target organ damage in pediatric research. Inadequate LVM indexing for body size due to scarcity of dual-energy X-ray absorptiometry (DEXA)-measured lean mass may lead to misclassification in the pediatric population. The only LVM indexed for DEXA-measured lean mass reference in children, mean age 11.6 yr, is 3-decades old and accurate LVM indexing in postpubertal adolescents and young adults is nonexistent. We generate new sex-specific LVM indexed for lean mass percentiles in healthy adolescence and young adulthood and correlated them with surrogates for normalizing body size. From the Avon Longitudinal Study of Parents and Children UK birth cohort, 868 adolescents (531 females) aged 17 yr were followed up for 7 yr. Lean mass was measured by DEXA at both time points. Echocardiography M-mode, two-dimensional (2-D), and three-dimensional (3-D) echo data for estimating LVM were collected at baseline and follow-up. Over 7 years, LVM increased in males (177.1 g) and females (133.5 g) at 17 yr to 199.9 g (males) and 145 g (females) at 24 yr. LVM/height ³ and LVM/height ^2.7 provided the most consistent cross-sectional and longitudinal intraclass correlation coefficients with LVM/lean mass in both sexes (0.90–0.93). Indexing LVM by lean mass eliminated the sex difference only at age 24 yr but not at 17 yr. LVM/height ^2.7 85 ^th percentiles for males and females at age 17 yr were 45.1 g/m ^2.7 and 41.4 g/m ^2.7, respectively, and at age 24 yr the 75 ^th percentiles were 45.5 g/m ^2.7 and 41.7 g/m ^2.7, respectively. The 95 ^th percentiles for males and females at age 17 yr were 49.5 g/m ^2.7 and 46.8 g/m ^2.7, respectively, and at age 24 yr were 57.1 g/m ^2.7 and 50.2 g/m ^2.7, respectively. These new reference percentile cut points were higher than the currently used 95 ^th percentile pediatric reference of 38.6 g/m ^2.7. Future studies are warranted in youth with clinical diseases to examine whether these new cut points provide a more accurate stratification of cardiovascular risk.

NEW & NOTEWORTHY Current left ventricular mass cut points for pediatric left ventricular hypertrophy are inaccurate. The inaccuracies are due, in part, to the average age of participants (11.6 yr) evaluated and also due to the lack of Echo and DEXA-measured body composition in postpubertal youth. Novel sex-based cut points are proposed for postpubertal youths at 17 and 24 yr. The new 95th percentile cut points are 15–20 g/m ^2.7 higher than the current cut point.