Defining ascending aorta dilatation in pediatric bicuspid aortic valve: Comparison of known classical and new z-score nomograms, and anthropometric parameters indexing for its assessment

Abstract

Background: Ascending aorta (AscAo) dilatation assessment and definition in pediatric bicuspid aortic valve (BAV) is challenging. We compared the Pediatric Heart Network (PHN) nomogram against the Halifax (HZ) one and analyzed their association with body surface area indexing (BSAI).

Methods: Echocardiographies from a national BAV registry were analyzed. AscAo and sinus of Valsalva, standardized using nomograms and BSAI, were compared by correlation and Bland-Altman tests. Nomogram +2 and + 3 z-scores thresholds contrasted against >21 mm/BSA-m2 by logistic regression and kappa agreement index. Age subgroup analysis was between adult-size (≥10 years and BSA ≥1.5 m²) and small children.

Results: A total 3858 reports were analyzed. The PHN nomogram resulted in higher AscAo z-scores (median 1.516 versus 1.413). Nomogram correlation was Rho_Spearman = 0.979 and Bland-Altman agreement bias was 0.302, with higher divergence in extreme z-scores. Patients ≥10 years and BSA ≥1.5 m² showed better concordance (bias -0.212 versus 0.440) despite similar correlation to the younger group. There was moderate but significant correlation amongst AscAo BSA-indexed diameters and PHN (Rho_Spearman = 0.514, p < 0.001) and HZ nomograms (Rho_Spearman = 0.366, p < 0.001), being higher in the older cohort than the younger, both by PHN (Rho_Spearmam 0.961 versus 0.424) and HZ (Rho_Spearman 0.952 versus 0.540). Higher area under the curve was obtained by PHN. A lower percentage was classified as dilated with PHN than by BSA-I in the adult-size cohort, but not in younger patients.

Discussion: There was good correlation and concordance between HZ and PHN nomograms, the latter resulting in higher z-scores. PHN has better agreement with BSA-I than HZ, with the PHN > +3 z-score threshold being the highest predictor for BSA-I dilatation definition, also showing higher specificity and sensitivity. BSA-I classified fewer patients as dilated than nomograms in adult-sized children but not in the younger cohort. Clinicians should be aware of this effect of BSA when normalizing diameters.

Keywords: Ascending aorta dilatation; Bicuspid aortic valve; Body surface area; Nomograms; Pediatrics.