title: Experimental validation of left ventricular transmural strain gradient with echocardiographic two-dimensional speckle tracking imaging.
abstract: OBJECTIVE
  To validate intramural strain measured by a speckle tracking imaging (STI) system against that measured by sonomicrometry crystals.
  
  
  RESULTS
  In 11 anaesthetized sheep, six sets of three sonomicrometry crystals were implanted in endo-, mid-wall, and epimyocardium on the anterior and lateral walls. Circumferential strain (CS) was calculated at three layers from endo-, mid-wall, and epicardial speckle. Radial strain (RS) was assessed for inner and outer halves of the myocardium. We compared ultrasound-derived strain measurements against those by sonomicrometry at baseline and during pharmacological stress and coronary occlusion. Intraclass correlation coefficients at baseline and during coronary occlusion were as follows: endocardial CS 0.80, 0.97; mid-wall CS 0.58, 0.89; epicardial CS 0.71, 0.81; endocardial RS 0.50, 0.78; epicardial RS 0.35, 0.83; and total RS 0.33, 0.71; respectively. At baseline, endocardial strains were higher than mid-wall and epicardial strains, resulting in an inner/outer wall RS gradient and inner/mid/outer wall CS gradients. Ischaemia caused significant reduction in all strains and disappearance of the strain gradient.
  
  
  CONCLUSIONS
  A newly developed STI system can accurately assess the intramural heterogeneity of CS distribution in normal and ischaemic myocardial segments and has the potential to become a non-invasive bedside tool for characterizing myocardial strain gradient.
authors.affiliation: Cardiovascular Division, Institute of Clinical Medicine, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8575, Japan. tomoco@md.tsukuba.ac.jp
authors.forename: Tomoko
authors.initials: T
authors.lastname: Ishizu
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Seo
authors.forename: Yoshiharu
authors.initials: Y
authors.lastname: Enomoto
authors.forename: Haruhiko
authors.initials: H
authors.lastname: Sugimori
authors.forename: Masayoshi
authors.initials: M
authors.lastname: Yamamoto
authors.forename: Tomoko
authors.initials: T
authors.lastname: Machino
authors.forename: Ryo
authors.initials: R
authors.lastname: Kawamura
authors.forename: Kazutaka
authors.initials: K
authors.lastname: Aonuma
mesh_terms: D000818:Animals; D004195:Disease Models, Animal; D004452:Echocardiography; D006352:Heart Ventricles / Q000000981:diagnostic imaging* / Q000503:physiopathology; D008297:Male; D012756:Sheep; D018487:Ventricular Dysfunction, Left / Q000000981:diagnostic imaging* / Q000503:physiopathology