Supplementary Material for: Cardiac Valve Annulus Diameters in Extremely Preterm Infants: A Cross-Sectional Echocardiographic Study

Background: With the increasing incidence of births of very preterm very-low-birth-weight infants, there is a demand for echocardiographic reference values of cardiac dimensions. Objectives: The aim of this study was to provide reference values of cardiac valve annulus diameters in a cohort of extremely preterm very-low-birth-weight neonates and to correlate these with patient characteristics. Methods: Valve diameters of 376 infants of < 32 weeks’ gestation and with a birth weight of ≤2,000 g were measured using 2-dimensional echocardiography. Correlations between valve diameters and patient characteristics (birth length/weight, body surface area, gestational age, and sex) were assessed. Birth weight was used to establish linear regression models. Inter- and intraobserver agreement was assessed through intraclass correlation coefficient (ICC) analysis. Results: Substantial variability was found (aortic valve mean [standard deviation; range]: 5.0 mm [0.6; 3.7–6.5]; pulmonic valve: 5.8 mm [0.8; 3.4–7.9]; mitral valve: 8.0 mm [1.0; 5.5–10.5]; tricuspid valve: 7.6 mm [1.2; 4.9–10.6]). There was a moderate correlation between birth weight and valve diameter (R² aortic valve: 0.36; pulmonic valve: 0.20; mitral valve: 0.24; tricuspid valve: 0.24). Adequate intraobserver (ICC range 0.74–0.91) and interobserver agreement (ICC range 0.77–0.89) was found. Conclusions: Our study provides ready-to-use reference values for cardiac valve annulus diameters for extremely preterm infants.