A z-score calculator for the ascending aorta (AAO), based on this article, is now available at ParameterZ.
The source article is relatively recent (2006) and confirms my own experience: z-score data for the ascending aorta are hard to find.
We provide for the first time a published regression equation for calculation based on BSA of the expected size of the ascending aorta in children, which allows calculation of z scores.
Their data is based on a sample of 88 normal patients- the sample size was chosen to match their group of patients with bicuspid aortic valve. Technically speaking, this sample size is too small to be used to construct reference values. The demographic data describing the reference population is not provided.
The manner of z-score prediction was modeled after Daubeney et al., for "consistency with the prediction equations... used for other structures in our echocardiographic laboratory". Personally, I think that the "transform both sides" technique (regressing the log of both the BSA and the AAO measurements) is perfectly reasonable for modeling this relationship. However, I continue to have misgivings about the patent substitution of the regression root mean square error for the sample standard deviation- particularly for the purpose of calculating a z-score.
In the absence of any other AAO z-score equations, I used the following two manners to cross-check the Halifax data:
- The "internally standardized" approach of Sheil et al., using the observed consistent ratio between the size of the AAO and the aortic annulus: 1.16. I used the Boston aortic valve z-score data in combination with their ratiometric approach- I call these the Derived AAO values.
- Data from UCLA was used to generate z-scores for an exploration of dilated aortic root in children with bicuspid aortic valves. Their published data provide us with a formula for predicting a height-based mean value for the AAO.
- Dilatation of the ascending aorta in paediatric patients with bicuspid aortic valve: frequency, rate of progression and risk factors.
- Warren AE, Boyd ML, O'Connell C, Dodds L. Heart. 2006 Oct;92(10):1496-500. Epub 2006Mar 17.
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- Validation and re-evaluation of a discriminant model predicting anatomic suitability for biventricular repair in neonates with aortic stenosis.
- Colan SD, McElhinney DB, Crawford EC, Keane JF, Lock JE. J Am Coll Cardiol. 2006 May2;47(9):1858-65. Epub 2006 Apr 17.
- Frequency of aortic root dilation in children with a bicuspid aortic valve.
- Gurvitz M, Chang RK, Drant S, Allada V. Am J Cardiol. 2004 Nov15;94(10):1337-40.
- Two-dimensional echocardiographic aortic root dimensions in normal children and adults.
- Roman MJ, Devereux RB, Kramer-Fox R, O'Loughlin J. Am J Cardiol. 1989 Sep1;64(8):507-12.
- Interpretation of echocardiographic measurements: a call for standardization.
- Vasan RS, Levy D, Larson MG, Benjamin EJ. Am Heart J. 2000 Mar;139(3):412-22.
- Relationship of the dimension of cardiac structures to body size: an echocardiographic study in normal infants and children.
- Daubeney PE, Blackstone EH, Weintraub RG, Slavik Z, Scanlon J, Webber SA. CardiolYoung. 1999 Jul;9(4):402-10.
