Regression Equations for Calculation of Z Scores of Cardiac Structures in a Large Cohort of Healthy Infants, Children, and Adolescents: An Echocardiographic Study

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Background

Decision making in the care of pediatric patients with congenital and acquired heart disease remains reliant on detailed measurements of cardiac structures using 2-dimensional echocardiography. Calculated z scores are often used to normalize these measurements to the patient's body size. Existing normal data in the literature are limited by small sample size, small numbers of measured cardiac structures, and inadequate data for the calculation of z scores. Accordingly, we sought to develop normative data in a large pediatric cohort using modern echocardiographic equipment from which z scores could be calculated.

Methods

Two-dimensional and M-mode echocardiography was performed in 782 patients ranging in age from 1 day to 18 years. Measurements were made of 21 individual cardiac structures. Regression equations were derived to relate the size of the various cardiac structures to body surface area. Data are presented graphically, and regression equations are derived relating cardiac dimension to body surface area.

Conclusion

The presented data will allow the calculation of z scores for echocardiographically measured cardiac structures. This information will be valuable for clinicians caring for infants and children with known or suspected cardiac disease.

Section snippets

Study Patients

The study population consisted of 813 patients aged 1 day to 18 years (median age 70 months) who were evaluated in the echocardiography laboratory at the Children's Hospital of Michigan between July 1, 2001, and September 30, 2003. Thirty-one patients had missing data for height or weight, leaving 782 patients available for analysis. Patients included in the study had no clinical, electrocardiographic, chest x-ray, or echocardiographic evidence of congenital or acquired cardiac disease. Most

Results

Table 2 shows the regression results for each of the 21 echocardiographic measurements on BSA. The information presented includes the estimated regression coefficients (β0, β1, β2, and β3) mean square error (MSE), and R2 value (coefficient of determination). R2 is the standard statistic used to measure how well data fit the selected regression model (goodness of fit) and has a value ranging from 0 to 1, with 1 representing a perfect fit and 0 representing a total lack of fit. Figure 1, Figure 2

Discussion

The detailed measurement of cardiac structures remains a crucial aspect in the management of children with various types of congenital and acquired cardiac disease. Decisions on the type and timing of interventions often rely to a large extent on these measurements. For example, the relative hypoplasia of a chamber or valve may dictate the choice of a 4-chamber repair versus a single-ventricle palliation. Similarly, chamber dilation from a congenital shunt lesion may be compared with these

Conclusions

We report the dimensions of 21 commonly measured cardiac structures in a large cross-sectional cohort of normal infants, children, and adolescents, relative to BSA. Regression equations are presented for the mean dimensions and variances across the range of body size. These equations may be used in the calculation of z scores that are commonly used in clinical decision making for pediatric patients with congenital or acquired cardiac disease.

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