title: Multilayer radial systolic strain can identify subendocardial ischemia: an experimental tissue Doppler imaging study of the porcine left ventricular wall.
abstract: OBJECTIVE
  This study investigates whether subendocardial ischemia can be detected by measuring multilayer radial systolic strain from epicardial tissue Doppler imaging.
  
  
  METHODS
  In 10 anesthetized open-chest pigs an extracorporeal shunt from the proximal brachiocephalic to the left anterior descending coronary artery was constricted in steps. Color microsphere injections and short axis Tissue Velocity Imaging (TVI) recordings were performed with open shunt, with a non-significant stenosis, and with 2 steps of shunt flow reduction.
  
  
  RESULTS
  With open shunt and no transmural flow gradient, there was a gradient of peak ejection strain with high values subendocardially for both 4 and 2 layer measurements. For 2 layer measurement strain was 56.0+/-10.5% subendocardially and 22.0+/-5.2% subepicardially. A non-significant stenosis, not altering transmural flow distribution, reduced strain to 40.3+/-5.4% in the endocardial half-layer. With reduced shunt flow resulting in subendocardial ischemia, peak ejection strain decreased further, primarily in inner wall layers, and postsystolic strain became evident. At severe stenosis (52.4+/-1.8% shunt flow reduction) strain was reduced to 3.8+/-3.6% in the subendocardium and 0.0+/-2.6% in the subepicardium.
  
  
  CONCLUSIONS
  Evaluation of myocardial function with multilayer radial systolic strain has a potential for detecting subendocardial ischemia.
authors.affiliation: Institute of Medicine, University of Bergen, Haukeland University Hospital, NO-5021 Bergen, Norway. knut.matre@med.uib.no
authors.forename: Knut
authors.initials: K
authors.lastname: Matre
authors.forename: Christian Arvei
authors.initials: CA
authors.lastname: Moen
authors.forename: Tord
authors.initials: T
authors.lastname: Fanneløp
authors.forename: Geir Olav
authors.initials: GO
authors.lastname: Dahle
authors.forename: Ketil
authors.initials: K
authors.lastname: Grong
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D004548:Elasticity; D004699:Endocardium / Q000000981:diagnostic imaging / Q000503:physiopathology; D007089:Image Enhancement; D007090:Image Interpretation, Computer-Assisted; D008863:Microspheres; D017202:Myocardial Ischemia / Q000000981:diagnostic imaging* / Q000503:physiopathology; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013314:Stress, Mechanical; D013552:Swine; D018608:Ultrasonography, Doppler