title: Histopathological validation of electromechanical mapping in assessing myocardial viability in a porcine model of chronic ischemia.
abstract: OBJECTIVE
  Left ventricular electromechanical mapping (EMM) determines myocardial viability on the basis of endocardial electrograms. The aim of the present study was to validate EMM in differentiating infarcted myocardium from viable myocardium by histopathological analysis.
  
  
  METHODS
  Sixty days after implanting an ameroid constrictor over the left circumflex artery to create chronic ischemia in 19 pigs, EMM was performed to construct unipolar voltage (UPV), bipolar voltage (BPV) and linear local shortening (LLS) maps. Noninfarcted and infarcted myocardium were identified by histopathology. Threshold determinations comparing noninfarcted tissue with scarred tissue were made by measuring the area under the receiver operating characteristic curves.
  
  
  RESULTS
  From the 19 hearts, 149 myocardial segments were divided into noninfarcted myocardium (n=128) and transmural infarct (n=21). UPV, BPV and LLS values (4.7+/-1.2 mV, 2.8+/-2.5 mV and 10.0+/-5.1%, respectively) of infarcted segments were significantly lower than those in noninfarcted myocardium (10.9+/-3.4 mV, 4.5+/-2.4 mV and 15.7+/-9.5%, respectively; P<0.01 for each comparison). The threshold values of UPV, BPV and LLS differentiating noninfarcted from infarcted myocardium were 6.2 mV (98% sensitivity, 95% specificity, 97% accuracy), 2.8 mV (80% sensitivity, 72% specificity, 79% accuracy) and 12.3% (68% sensitivity, 67% specificity, 68% accuracy), respectively. The relative dispersion of voltage was lower for UPV versus BPV.
  
  
  CONCLUSIONS
  UPV can accurately differentiate infarcted from noninfarcted tissue in the chronic ischemic heart of pigs; however, BPV and LLS results were less accurate.
authors.affiliation: Stem Cell Center, Texas Heart Institute at St Luke's Episcopal Hospital, Houston, Texas, USA.
authors.forename: Yi
authors.initials: Y
authors.lastname: Zheng
authors.forename: Marlos R
authors.initials: MR
authors.lastname: Fernandes
authors.forename: Guilherme V
authors.initials: GV
authors.lastname: Silva
authors.forename: Cristiano O
authors.initials: CO
authors.lastname: Cardoso
authors.forename: John
authors.initials: J
authors.lastname: Canales
authors.forename: Amir
authors.initials: A
authors.lastname: Gahramenpour
authors.forename: Fred
authors.initials: F
authors.lastname: Baimbridge
authors.forename: Maria
authors.initials: M
authors.lastname: da Graça Cabreira-Hansen
authors.forename: Emerson C
authors.initials: EC
authors.lastname: Perin