Coronary Artery Z Score Regression Equations and Calculators Derived From a Large Heterogeneous Population of Children Undergoing Echocardiography

Background: Clinical decision making in Kawasaki disease relies on measurements of the coronary arteries obtained by 2-dimensional echocardiography. Z scores relating measured values to independent variables are invaluable in ensuring the accurate and consistent treatment of patients with Kawasaki disease. Methods: The right coronary artery (RCA), left main coronary artery (LMCA), and left anterior descending (LAD) coronary artery were measured in 432 normal digital echocardiograms from a heterogeneous population of normal subjects aged 0 to 20 years. Linear regression analyses were performed relating the measurements to various functions of independent variables, including body surface area (BSA), height, and height(2.7). The adjusted R-2 and mean square error values were compared for each of the models, and the best model was chosen to create a Z score calculator. Results: Using the model ln(measurement) = beta(1) + beta(2) X ln(BSA), the adjusted R-2 values were 0.638, 0.702, and 0.708 for the RCA, LMCA, and LAD coronary artery models, respectively, with mean square error < 0.0402. Conclusion: The calculation of accurate Z scores for coronary artery measurements in children can be accomplished using the Z-score calculator. (J Am Soc Echocardiogr 2009; 22: 159-164.)