Echo Z-Score & Normal Electrocardiogram

(Observational Study)

Study Summary

The objectives of this study were:

  • To establish normal values for common echo measurements in a racially diverse population of normal children from multiple centers over a wide geographic area.
  • To collect electrocardiograms (ECG) from the same population of normal children for future establishment of ECG reference values.

3566 Charts Reviewed

Data were collected on 3566 healthy nonobese children ≤18 years of age with normal echocardiograms.

Best Predictor Identified

Body size was found to be the best predictor of the sizes of cardiovascular structures, and age, sex, and race did not have a clinically significant effect on this relationship.

Calculator Available

The PHN z-scores are available in an online Z-score calculator.

What was the study about?

Echocardiography (echo) is crucial for the evaluation of children with congenital and acquired heart diseases. It is the primary way to see heart structures to establish diagnoses, determine treatment options, monitor disease progression, and assess the effects of intervention. The sizes of hearts and blood vessels are frequently affected by the abnormal way that blood flows in children with malformed heart structures. Treatment decisions rely on an accurate determination of cardiovascular size, which is an important component of this echo study. Accurate, normal values must be available for clinicians to distinguish a normal finding from an abnormal one and to determine if the size of a structure is adequate, too small, or too large to function effectively.

The Z-score tells us how far above or below the score is from the mean. Similar to growth charts, they allow comparisons of cardiac measurements obtained for an individual child with measurements obtained from a normal population adjusted for the effects of body size, age, gender, and/or race.

Who was in the study?

Patients less than or equal to 18 years of age with echo images performed after January 1, 2008. Patient records must also have documented height, weight, gender, and race.

What happened during the study?

This study was based on a retrospective chart review. This is what was done in the study:
  • We calculated the mean for common echo measurements adjusted for body size, age, gender, and race for a large group of normal children from multiple centers.
  • We also evaluated the effects of ethnicity on echo measurements.
  • We developed a repository of ECGs obtained from normal children that will be used to establish pediatric ECG reference values.

What were the results of the study?

  • Age, sex, and race do not have a clinically significant effect on the relationship between the sizes of cardiovascular structures and body size.
  • Body surface area (BSA) is a good measure to use for evaluating the effect of body size on the sizes of cardiovascular structures.
  • Z-scores for common pediatric echo measurements based on BSA alone are available in an online Z-score calculator.

Study Publications

  • Relationship of Echocardiographic Z Scores Adjusted for Body Surface Area to Age, Sex, Race, and Ethnicity: The Pediatric Heart Network Normal Echocardiogram Database

    L. Lopez, Circ Cardiovasc Imaging 2017; 10(11):e006979.

    Data were collected on 3566 healthy nonobese children ≤18 years of age with normal echocardiograms to produce reference values for echocardiogram measurements based on age, sex, race, ethnicity, height and weight. Body size was found to be the best predictor of the sizes of cardiovascular structures, and age, sex, and race did not have a clinically significant effect on this relationship.

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  • Electrocardiograms in Healthy North American Children in the Digital Age

    E.V. Saarel, Circ Arrhythm Electrophysiol 2018 Jul;11(7):e005808.

    Electrocardiography is a cornerstone in the cardiac evaluation of children. Wide variation in previously published data, much of which was obtained before the digital era, provided a strong motivation to obtain more reliable data on electrocardiogram (ECG) measurements in healthy children from North America. This study found that most ECG measurements varied by sex and race and differed from prior studies done in smaller, more racially and ethnically homogeneous populations. This study provides valuable data that can be used clinically for interpreting pediatric ECGs in the modern era for diagnosis or screening of heart disease in North America, particularly for Long QT syndrome and left ventricular hypertrophy.

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  • Challenges With Left Ventricular Functional Parameters: The Pediatric Heart Network Normal Echocardiogram Database

    P. C. Frommelt, J Am Soc Echocardiogr. 2019 Oct;32(10):1331-1338.e1.

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  • Challenges and lessons learned from the Pediatric Heart Network Normal Echocardiogram Database study

    D. Truong, Cardiol Young. 2020 Apr;30(4):456-461.

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