Copyright © 2005, The European Society of Cardiology
Letter to the Editors
Echonet, 317 Kifissias Avenue, Kifissia, 145 61 Athens, Greece
g.outroulis{at}echonet.gr
* Tel.: +30 210 6205 129; fax: +30 210 6205 119.
Dear Sir,
I read the very interesting paper of Storaa et al.1 which was published in the October 2004 issue. The researchers presented a new imaging technique of the left ventricle, tissue motion imaging (TMI), which allows visual and quantitative interpretation of regional tissue velocity, acceleration, displacement and strain for the whole cardiac cycle in one image.
Regarding the calculation of strain from TMI images the authors derived their data using the formula of one-dimensional Lagrangian strain 
=(L–L0)/L0.1 This formula describes a load–elongation relationship, and can be applied only for metals to test their linear elasticity (plasticity) under certain load, and not for living tissues.2 It is well established that living soft tissues are nonlinearly elastic (pseudoelastic), multiphase, nonhomogenous, and anisotropic materials.2,3 Cardiac muscle is an exponential type of material with viscoelastic properties, and a nonlinear stress–strain relationship should be used to describe its nonlinear elasticity.4–6
Therefore the above mentioned linear strain formula should not be used in TMI images for quantitative interpretation of strain. Nevertheless TMI seems to be a very promising technique for the qualitative assessment of the regional systolic and diastolic function of the left ventricle.
Yours faithfully,
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References |
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 Top References |
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- Storaa C., Cain P., Olstad B., Lind B., Brodin L.Å. Tissue motion imaging of the left ventricle – quantification of myocardial strain, velocity, acceleration and displacement in a single image. Eur J Echocardiogr (2004) 5:375–385.
[Abstract/Free Full Text] - Fung Y.C. A first course in continuum mechanics. (1977) 2nd ed. Englewood Cliffs, NJ, USA: Prentice-Hall, Inc.
- Fung Y.C., Fronek K., Patitucci P. Pseudoelasticity of arteries and the choice of its mathematical expression. Am J Physiol (1979) 237:H620–H631.[Web of Science][Medline]
- Waldman L.K., Fung Y.C., Covell J.W. Transmural myocardial deformation in the canine left ventricle. Normal in vivo three-dimensional finite strains. Circ Res (1985) 57:152–163.
[Abstract/Free Full Text] - Mirsky I., Parmley W.W. Assessment of passive elastic stiffness for isolated heart muscle and the intact heart. Circ Res (1973) 33:233–243.
[Abstract/Free Full Text] - Omens J.H., Fung Y.C. Residual strain in rat left ventricle. Circ Res (1990) 66:37–45.
[Abstract/Free Full Text]
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