Doppler strain rate echocardiography versus magnetic resonance imaging.

Editor must not exceed 400 words in length and must be limited to three authors and five references. They should not have tables or figures and should relate solely to an article published in Circulation within the preceding 12 weeks. Authors of letters selected for publication will receive prepublication proofs, and authors of the article cited in the letter will be invited to reply. Replies must be signed by all authors listed in the original publication. Please submit three typewritten, double-spaced copies of the letter to Herbert L. Fred, MD, ࡆ the Circulation Editorial Office. Letters will not be returned. To the Editor: In the recently published article by Edvardsen et al 1 in Circulation where Doppler strain rate (SDE) was compared with magnetic resonance imaging (MRI) tissue-tagged strain rate imaging, it is a significant loss for the readers that the differences in strains obtained from MRI and SDE were glossed over so casually by the authors. As stated in the article, strain is the time integral of incremen-tal strain rate. One assumes SDE performs this time integral for a small area on the echocardiographic image, with various sections of heart tissue moving through that small area during the heart cycle (ie, Doppler imaging cannot yet " track " tissue through the heart cycle), whereas MRI performs this time integral between " fixed " sections of heart tissue moving away or toward one another. One analogy of SDE is that of observing a small area of a river from the banks of the river (Eulerian method of description) versus MRI, which is more akin to observing a small area of river while floating on the river (Lagrangian method of description). 2 Even if " the limits of agreement between the techniques were relatively small, " the 2 techniques are not measuring the same variable. If the 2 variables have a consistent relationship, as shown nicely in this study, then it should be stated as such. 1. Edvardsen T, Gerber BL, Garot J, et al. Quantitative assessment of intrinsic regional myocardial deformation by Doppler strain rate echo-cardiography in humans: validation against three-dimensional tagged magnetic resonance imaging. Response The comment from Dr DeGroff on our recently published article 1 relates to the fundamental difference between measuring strain by Doppler echocardiography, where measurements are taken from a fixed point in space, and measuring strain by tagged magnetic resonance imaging (MRI), where measurements are …