Reference Curves for the Aortic Area by Age

The aim of this study was to establish reference curves and formulas for aortic cross-sectional area in patients from infancy to young adulthood.Patients (aged 2 days to 18.1 years) who underwent electrocardiographically gated cardiac computed tomography between May 2004 and December 2011 were retrospectively examined. These patients were further divided into a group of normal controls (without aortic disease) and a group with coarctation of aorta. In the group of normal controls, the cross-sectional area of the aorta was measured at six locations: the sinotubular junction, distal ascending aorta, proximal arch, distal arch, aortic isthmus, and descending aorta (DAO). Interobserver and intraobserver variability, gender differences, the relationship between aortic cross-sectional areas and age, and the ratio to the DAO were also examined. The area ratio to the DAO was also examined in the group with coarctation of the aorta.A total of 65 patients and 365 measurable aortic segments were included in the analysis (55 normal controls and 10 patients with coarctation of aorta). Interobserver and intraobserver variability was limited (aside from measurements of the sinotubular junction). There were no gender differences in age and the cross-sectional areas of the different aortic segments. In the group of normal controls, the cross-sectional area of each aortic segment was highly correlated with age (all0.90, P.001). The reference curves and formulas for aortic cross-sectional area by age were also determined for further clinical use. In the normal controls, the95% confidence intervals of the ratios of aortic isthmus to DAO, distal arch to DAO, and proximal arch to DAO were approximately 0.6, 0.8, and 1.0, respectively. In addition, in the group with coarctation, all area ratios of aortic isthmus to DAO were0.6, which was significantly different from the group of normal controls (P.001). The area ratios of distal arch to DAO and proximal arch to DAO were also significantly different between two groups (P.001 for both).Measurement of aortic area was reproducible. The established reference curves and formulas and minimal area ratios were convenient for further clinical use.