Coronary Normograms and Coronary-aortic Ratio for Determination of Coronary Dilatation

Echocardiographic measurements of the internal diameter of the left (LCA) and right (RCA) main coronary arteries were performed on 390 children (215 male, 175 female) with normal cardiac structures, who were within the ages of 2 months to 8 years. They have normal clinical examination and complete echocardiographic examination prior to enrollment for the study. The maximal internal diameters within the cardiac cycles were measured at a distance of 5 to 10 mm from the origins of the LCA and RCA.The racial composition of the study population comprises 73.3% Chinese, 17.4% Malay, 6.2% Indian and 3.1% others. Their mean age was 34 months (range 2 to 106 months). The mean weight and height were 13.0 ± 6.0 kg and 88.6 ± 20.9 cm, respectively. After controlling for age, height, weight and body surface area (BSA), the LCA and RCA diameters were larger in boys (mean difference 0.1mm, p < 0.005). The diameter of the LCA and RCA correlated linearly with age, height, weight and BSA (Pearson R > 0.8, p < 0.005). The regression equations, prediction graphs and z-score graphs are given. For the same patient, the LCA is generally larger than the RCA (mean difference 0.30 ± 0.21mm; mean percentage difference 16 ± 12.5%, p < 0.005). The LCA-to-aortic annulus (LCA/Ao) and RCA-to-aortic annulus (RCA/Ao) ratio fall within a narrow range that is independent of sex, weight, height or body surface area. The LCA/Ao ratio = 0.15 ± 0.02 (range 0.09 to 0.21), and RCA/Ao ratio = 0.13 ± 0.02 (range 0.09 to 0.20). Conclusion: The regression equations and normograms for the LCA and RCA will serve as useful guides to determine coronary abnormalities, especially in children with Kawasaki Disease. The LCA/RCA-aortic ratio can serve as a quick index to detect coronary dilatation/ectasia.