Echo Z-Score Suggested Reading

 

Lots of people have asked me something like:

We are finding discrepancies in Z scores calculated by your method and the Z scores calculated by software provided by Boston...
WHY ?

I usually feel obligated to first set the record straight: these are not my z-score calculations. They are calculators based upon published literature, and I cite the source literature on the same page as the calculator... In some cases it is clear that this misconception is a language barrier issue, and I must apologize for that. English is the only language I know (well, apart from some Spanish, but most of that I can't repeat in polite company).

To really answer the question I have to admit: I don't really have all the words, or even some of the right words, and I am basically incapable of organizing them in a meaningful order.

Fortunately, the lucid discussion about reference values for pediatric echo, the matters of predicting echo normal values, and the general application of z-scores towards pediatric cardiology has already been done– and by people far brighter and more eloquent than me. I have read and (mostly) understand, and I therefore highly recommend, the following:

• the invited editorial Establishing norms for echocardiographic measurements of cardiovascular structures and function in children
• the original article Theoretical and empirical derivation of cardiovascular allometric relationships in children
• the excellent chapter in Nadas' Pediatric Cardiology: Methodological Issues in Clinical Research
• the recent work, A Novel Method of Expressing Left Ventricular Mass Relative to Body Size in Children

Why are your z-scores different? I don't know for sure, but I can take some guesses. Certainly, I recognize that there are differences.

The inevitable, and, possibly, better question is "Which one is most correct ?"

Universal Z-Score Calculations

According to the Spring issue of the ASE's Pediatric and Congenital Heart Disease Council News, interesting things are afoot:

The council has developed a Normative Database working group... to develop consensus methods for standardization of measures acquired during the pediatric echocardiogram with a long-term goal of creating a normative database of universally available standardized z-score calculations for the pediatric and young adult population.

I have toyed around a bit with making a few z-score calculators for pediatric echo universally available, and in the process one thing became clear: we are a long way from a consensus on z-scores. And, while enormously useful, the z-score calculators by themselves seem to only scratch the surface of what is now possible.

What is truly fascinating to me is the idea of a universal normative database. While I have yet to implement such a design through ParameterZ.com, what I have learned is: technology is not a barrier to creating an online pediatric echo reference values database.

What would be really cool is to marry the reference values with something that would...

... allow participants to create and generate web-based, secure echo reports that are standardized and complete.

(That is the ASE's promised echo toolbox reporting tool).

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I have been contemplating the concept of web based pediatric echo z-scores and standardized echo reports for some time.

I have to say that I am excited and eager to see what more and greater minds come up with.

Fetal Ventricular Wall Dimensions

Reference values for fetal ventricular wall thickness are not easy to come by. This gadget is based on one of few available references.

Evaluation of Fetal Heart Dimensions from 12 Weeks to Term
Cora Firpo, MD, Julien I.E. Hoffman, MD, and Norman H. Silverman, MD
Am J Cardiol 2001 [link]

Measurements of the ventricular walls and septum were made from the "4-chamber" views, below the coapted AV valve leaflets, in diastole.