Agreement between Z-score and an arch-to-ascending aorta ratio derived from CT angiography for detection of aortic arch hypoplasia

Zhanar Moldakhanova

2025

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DOI 10.54500/2790-1203-2025-6-125-amj002
Data confidence 70 medium
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Abstract

Background.Aortic arch hypoplasia (AAH) is an important congenital cardiovascular abnormality that requires accurate anatomical characterization for appropriate surgical planning. Computed tomography angiography (CTA) provides high-resolution measurements of the ascending aorta and transverse aortic arch; however, different diagnostic criteria may classify hypoplasia inconsistently.Objective.This study aimed to compare the agreement between a Z-score-based definition of AAH and a ratio-based morphologic criterion derived from CTA measurements.Methods.This retrospective study included 48 pediatric patients with clinically confirmed AAH who underwent CTA. The ascending aorta diameter, transverse aortic arch diameter, and the arch-to-ascending aorta (Arch/AAo) ratio were obtained from multiplanar reformatted CTA images. Hypoplasia was defined using two approaches: (1) Z-scores (≤ −2), and (2) a ratio-based criterion (Arch/AAo < 0.50). Summary statistics were computed for all measurements, and agreement between methods was assessed using percent agreement, Cohen’s κ, and McNemar’s test. Results.The mean ascending aorta diameter was 0.95 ± 0.46 cm, the mean transverse arch diameter was 0.50 ± 0.27 cm, and the median Arch/AAo ratio was 0.50 (IQR 0.43-0.65). The Z-score method classified 47 of 48 patients (97.9%) as hypoplastic, whereas the ratio criterion identified 18 patients (37.5%) as hypoplastic. Agreement between methods was 44.2%, with a Cohen’s κ of 0.03, indicating minimal concordance beyond chance. McNemar’s test demonstrated significant disagreement between classifications (χ² = 22.04).Conclusion.The Z-score and Arch/AAo ratio methods differ substantially in how they classify AAH. While Z-scores incorporate normative size adjustment, the ratio criterion reflects anatomical proportionality and identifies a more selective subset of patients with marked transverse arch narrowing. Clinicians should recognize these methodological differences when assessing AAH and selecting criteria for diagnosis or surgical decision-making.Keywords: aortic arch hypoplasia,congenital heart defects,computed tomography angiography,Z-score,aortic ratio,pediatric cardiovascular imaging,aortic measurements,diagnostic agreement.