Monday, April 1, 2013

Pretty Useless Surface Charts

a quick update about newly available aortic root reference values.

I read the fairly recent AJC article Normal limits in relation to age, body size and gender of two-dimensional echocardiographic aortic root dimensions in persons ≥15 years of age and struggled to make use of their “surface charts”- maybe you did too. Here is an example “surface” representing “aortic diameters” (I presume they mean the sinus of Valsalva) for females:


At first, I thought it was intended to serve as a nomogram, i.e., that this device is what we are supposed to use to check our measured values against... but clearly that is impossible.

Mostly, this is just a simple demonstration of how the authors are communicating to us that aortic diameters increase with both body size and age. You should definitely not try to interpolate reference values from this- you’ll go cross-eyed, almost for sure.

I double-dog dare you to come up with a value for someone in the middle of those axes- say a 45 year old, 160 cm person.

Instead, try this:

I put together a quick tool that will help you find the correct reference values for the aortic root (aortic valve and sinus of Valsalva) that are gender-specific age- and size-adjusted. For instance, here are the calculated values for the previously mentioned and difficult-to-interpolate 160 cm, 45 year old female:

I did not incorporate these new calculations into the existing ones for a couple of reasons, not the least of which is time. The other concerns are that these new values are mainly for adults (all subjects were >=15yrs), and that these calculations are multi-factorial (age, size, and gender) and would have required a major re-work of the interface, for which I do not have the time. I hope to do some rough comparisons sometime in the future, but for now I hope they are useful for those that deal with adult patients, both young and old.