title: Defining the transmurality of a chronic myocardial infarction by ultrasonic strain-rate imaging: implications for identifying intramural viability: an experimental study.
abstract: BACKGROUND
  In a correlative functional/histopathologic study, we investigated the regional deformation characteristics of both chronic nontransmural and transmural infarctions before and after a dobutamine challenge.
  
  
  RESULTS
  After stenosing copper-coated stent implantation to produce circumflex artery endothelial proliferation, 18 pigs were followed up for 5 weeks. Posteuthanasia histology showed 10 to have a nontransmural and 8 a transmural infarction. Eight nonstented animals served as controls. Regional radial function was monitored by measuring ultrasound-derived peak systolic strain rates (SR(SYS)) and systolic strains (epsilon(SYS)) (1) before stent implantation and (2) at 5 weeks, at baseline (bs) and during an incremental dobutamine infusion. In controls, dobutamine induced a linear increase in SR(SYS) (dobutamine: bs, 4.8+/-0.4 s(-1); 20 microg x kg(-1) x min(-1), 9.9+/-0.7 s(-1); P<0.0001) and an initial increase of epsilon(SYS) at low dose (bs, 58+/-5%; at 5 microg x kg(-1) x min(-1), 78+/-6%; P<0.05) but a subsequent decrease during higher infusion rates. In the nontransmural group, bs SR(SYS) and epsilon(SYS) were significantly lower than prestent values (SR(SYS), 2.9+/-0.5 s(-1) and epsilon(SYS), 32+/-6%, P<0.05 versus prestent). During dobutamine infusion, SR(SYS) increased slightly at 5 microg x kg(-1) x min(-1) (4.7+/-0.6 s(-1), P<0.05) but fell during higher infusion rates, whereas epsilon(SYS) showed no change. For nontransmural infarctions, transmural scar extension correlated closely with epsilon(SYS) at bs (r=0.88). For transmural infarctions, SR(SYS) at bs was significantly reduced and epsilon(SYS) was almost not measurable (SR(SYS), 1.8+/-0.3 s(-1); epsilon(SYS), 3+/-4%). Both deformation parameters showed no further change during the incremental dobutamine infusion.
  
  
  CONCLUSIONS
  Ultrasonic deformation values could clearly differentiate chronic nontransmural from transmural myocardial infarction. The transmural extension of the scar could be defined by the regional deformation response.
authors.affiliation: Department of Cardiology, University Hospital Gasthuisberg, Leuven, Belgium.
authors.forename: Frank
authors.initials: F
authors.lastname: Weidemann
authors.forename: Christoph
authors.initials: C
authors.lastname: Dommke
authors.forename: Bart
authors.initials: B
authors.lastname: Bijnens
authors.forename: Piet
authors.initials: P
authors.lastname: Claus
authors.forename: Jan
authors.initials: J
authors.lastname: D'hooge
authors.forename: Paul
authors.initials: P
authors.lastname: Mertens
authors.forename: Eric
authors.initials: E
authors.lastname: Verbeken
authors.forename: Alex
authors.initials: A
authors.lastname: Maes
authors.forename: Frans
authors.initials: F
authors.lastname: Van de Werf
authors.forename: Ivan
authors.initials: I
authors.lastname: De Scheerder
authors.forename: George R
authors.initials: GR
authors.lastname: Sutherland
mesh_terms: D000818:Animals; D002470:Cell Survival; D002908:Chronic Disease; D004195:Disease Models, Animal; D004280:Dobutamine; D004452:Echocardiography; D025401:Echocardiography, Stress; D006321:Heart / Q000187:drug effects; D006439:Hemodynamics / Q000187:drug effects; D009200:Myocardial Contraction / Q000187:drug effects; D009203:Myocardial Infarction / Q000145:classification* / Q000175:diagnosis* / Q000473:pathology; D011237:Predictive Value of Tests; D015607:Stents; D013314:Stress, Mechanical; D013552:Swine; D013599:Systole; D014055:Tomography, Emission-Computed
chemical_list: D004280:Dobutamine