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Adriana Saltijeral, Leopoldo Perez de Isla, Obese children and myocardial deformation changes: some discrepancies but a large number of common points, European Heart Journal - Cardiovascular Imaging, Volume 15, Issue 4, April 2014, Page 473, https://doi.org/10.1093/ehjci/jet264
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We read with interest the article entitled ‘Alterations of left ventricular myocardial strain in obese children’ by Labombarda et al.1 regarding the use of two-dimensional (2D) strain imaging to study whether severely overweight children show early abnormalities in myocardial function.
First of all we would like to point out that we published an article with a similar population and similar results 2 years ago.2 We also would like to make some comments with the intention to help to understand the results. In our study, we used three-dimensional wall motion tracking (3D-WMT) technology (Artida system, Toshiba Medical Systems, Japan) instead of 2D speckle tracking technology. We found a decrease in left ventricular longitudinal and circumferential strains but an increase in radial strain, with a maintained left ventricular ejection fraction. As the authors say in the article, when using the 2D strain technology, ‘radial strain is calculated perpendicularly at the longitudinal motion and is very influenced by the longitudinal out-of-plane motion, much more than the field of circumferential motion’. We think they are completely right as it is one of the main limitations of the 2D speckle tracking technology. The new 3D-WMT technology allows us to avoid this problem as it follows the speckles in a volume and not in a plane. From our point of view, this could be the reason why we found an increase in the radial strain in obese children and Labombarda et al. did not. A decrease in the longitudinal and circumferential strain might be accompanied by an increase in the radial strain in order to maintain the global left ventricular ejection fraction. This fact probably represents a compensation mechanism in early stages of disease. Early impairment of left ventricular subendocardial layers may be the reason for this reduction in the longitudinal and circumferential strain. Nevertheless, radial strain is less dependent on this subendocardial region and may increase to maintain the left ventricular ejection fraction. Keeping in mind all these concepts, we think that our results explain how a decrease in the longitudinal strain plus a decrease in the circumferential strain may coexist with a preserved left ventricular ejection fraction, as we and Labombarda et al. show in our respective results.
