European Journal of Echocardiography Advance Access published online on March 14, 2008
European Journal of Echocardiography, doi:10.1093/ejechocard/jen110
Derivation of a size-independent variable for scaling of cardiac dimensions in a normal paediatric population
1 Cardiac Ultrasound Laboratory, Cardiology Division, Department of Medicine, Massachusetts General Hospital, Harvard Medical School, 55 Fruit Street, YAW-5E, Boston, MA 02115-2696, USA
2 Cardiovascular Research Center, Cardiology Division, Department of Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA
3 Division of Preventive Medicine, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA
Received 17 October 2007; .
* Corresponding author. Tel: +1 617 724 1993; fax: +1 617 643 1639. E-mail address: aeweyman{at}partners.org
 |
Abstract |
|---|
Aims: It is general practice to correct cardiac chamber size for body size by the process of scaling or normalization. Normalization is most commonly performed using simple linear or isometric correction; however, there is increasing evidence that this approach may be flawed. Likewise, there is little agreement concerning the appropriate scaling variable (measure of body size) for normalization. Therefore, we aimed to establish the optimal method for correcting the differences in body size in a large population of echocardiographically normal paediatric subjects.
Methods and results: We compared the relative ability of standard size variables including height (HT), body weight (BW), body mass index (BMI), and body surface area (BSA), in both isometric and allometric models, to remove the effect of body size in 4109 consecutive echocardiographically normal subjects <18 years of age, using the left atrial dimension (LAD) as a reference standard. Simple linear normalization resulted in significant residual correlations (r = –0.57 to –0.92) of the indexed value with the body size variable, the correlations with weight (WT) and BSA actually increasing. In contrast, correction by the optimal allometric exponent (AE) removed the effects of the indexed variable (residual correlations –0.01 to 0.01), with BW and BSA best removing the effects of all the measures of body size.
Conclusion: Conventional linear correction for body size is inaccurate in children and paradoxically increases the relationship of the indexed parameter with WT and BSA. Conversely, correction using the optimal AE removes the effect of that variable, with WT best correction for all measures of body size.
Keywords: Scaling; Allometric; Echocardiography; Linear; Classification
Both authors contributed equally to this work.