Z-Score Calculators for Cross Sectional Area to Height Ratio of the Aortic Root and Ascending Aorta in Healthy Children

In pediatrics, echocardiographic measurements of the aorta are normalized using body surface area (BSA), which do not account for differences in body composition amongst children or as they grow. Height has been shown to have a linear relationship with measures of aortic size in pediatrics. Data from the Pediatric Heart Network (PHN) Echo Z-Score database was used to develop z-scores for cross sectional area to height ratio (CSA/ht) on 3215 healthy pediatric patients ≤ 18 years old. Aortic root and ascending aorta CSA/ht (cm 2 /m) were calculated. Linear regression was performed to assess the relationship between patient sex, age at echocardiogram, and CSA/ht of the aortic root. An interaction term was included to allow the effect of age to vary by sex. Estimates from the final regression model were utilized in the z-score calculator. An identical analysis was repeated for ascending aorta CSA/ht. Older children had larger aortic root CSA/ht (β = 0.10, p < 0.001) and ascending aorta CSA/ht (β = 0.08, p < 0.001). Male children had larger aortic root CSA/ht (β = 0.13, p < 0.001) and ascending aorta CSA/ht (β = 0.08, p < 0.001). There was a significant interaction of sex and age in the aortic root model (β = 0.015, p < 0.001), but not in the ascending aorta model (β = 0.003, p = 0.16). We created two z-score calculators for CSA/ht of the aortic root and the ascending aorta in normal children, ideally allowing for more accurate assessment of aortic size in children.