New equations and a critical appraisal of coronary artery Z scores in healthy children.

BACKGROUND: The aim of this study was to find the best model to obtain valid and normally distributed Z scores for coronary artery (CA) diameters in a large, heterogeneous population of healthy children.

METHODS: Echocardiography was performed on 1,033 healthy children. Several regression models were tested with height, weight, body surface area, and aortic valve diameter. The computed Z scores were tested for normal distribution and stability.

RESULTS: CA diameter was best predicted using regression with the square root of body surface area. The weighted least squares method yielded normally distributed and very stable Z-score estimates for all CA segments. In prepubertal children, aortic valve diameter was also a valid predictor of CA diameter.

CONCLUSIONS: This study shows two valid methods to estimate Z scores for CA size in children of all ages. Such Z scores are important for risk stratification in patients with Kawasaki disease.