Echo Z-Score Study Basics

Echocardiography is crucial for the evaluation of children with congenital and acquired heart diseases. It is the primary imaging modality for establishing diagnoses, determining treatment options, monitoring disease progression, and assessing the effects of intervention. The sizes of cardiovascular structures are frequently affected by the abnormal hemodynamics of a disease state, particularly in children. Because treatment decisions rely on an accurate determination of cardiovascular size, quantification is an important component of the echo study. Reliable, accurate, and generalizable normal reference values must be readily 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. In addition to their importance in the clinical setting, reference values are also used to define the population of interest and as primary or secondary outcomes in research studies designed to evaluate medical or surgical therapies.

Previous studies suggest that measurements in normal children are confounded by body size, age, gender, and race. Adjustments must be made for these factors before the effect of a disease state on the cardiovascular system can be assessed. Echo Z-scores have gained widespread acceptance in both clinical practice and research in pediatric cardiology. 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.

The Z-score tells us how many standard deviations (SDs) the observation is from the mean, and it is positive or negative according to whether the observation lies above or below the mean. It can be calculated from various subpopulations based on a particular set of parameters (including body size, age, gender, and race).

The objectives of this study are:
  • To establish a Z-score database for common echocardiographic (echo) measurements based on a uniformly defined and 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

Who can be in the study?

Patients less than or equal to 18 years of age with echo images in in DICOM (Digital Imaging and Communications in Medicine) format from studies performed after January 1, 2008. Patient records must also have documented height, weight, gender, and race.

What do we have to do to be in the study?

This study is retrospective chart review; therefore we will not be actively recruiting participants.

This is what needs to be done in the study:
  • We will calculate the mean and standard deviation (SD) for common echo measurements adjusted for body size, age, gender, and race for a large group of normal children using retrospective data from multiple centers.
  • Determine the best body surface area (BSA) calculation method for describing the relationship between BSA and the sizes of cardiovascular structures.
  • Evaluate the effects of other potential confounders such as height, weight, body mass index (BMI), and ethnicity on echo measurements.
  • Develop a repository of ECGs obtained from normal children that would be used to establish robust pediatric ECG reference values.

How long will we be in the study?

This chart review study will last for approximately 24 months.

What are the possible benefits to being in this study?

At present, both clinical decision-making and the conduct of research are affected by the limitations of current Z-score nomograms. To date, normal reference values for echo measurements obtained from multiple centers and geographic locations and adjusted for body size, age, gender, and race do not exist, and a multicenter study to determine these Z-scores for a large and racially diverse population of normal children is warranted.

What are the possible risks to being in this study?

There are no risks associated with echocardiography.

What are the costs to me to be in the study?