title: Transmural and endocardial Purkinje activation in pigs before local myocardial activation after defibrillation shocks.
abstract: BACKGROUND
  Earliest recorded postshock myocardial activations in pigs originate in the subepicardium of the apex and lateral free wall of the left ventricle (LV) 30-90 ms after the shock.
  
  
  OBJECTIVE
  The purpose of this study was to determine whether the Purkinje system is a candidate for the source of postshock activations by performing endocardial and transmural postshock activation mapping.
  
  
  METHODS
  In five pigs, 32 plunge needles with 12 electrodes (1-mm spacing) were inserted into the LV apex and lateral free wall. Up to 70 plunge needles with six electrodes (2-mm spacing) were spread throughout the remainder of the LV, while 9-12 plunge needles with four electrodes (2-mm spacing) were inserted into the right ventricle. A basket catheter with 32 bipolar recording sites was inserted into the LV. Defibrillation-threshold (DFT)-level shocks were delivered during 10 episodes of electrically induced ventricular fibrillation. Electrograms of postshock activation cycles were analyzed for Purkinje and myocardial activations.
  
  
  RESULTS
  Purkinje activations were recorded before local myocardial activation in 9% of basket electrograms and in 15% of plunge needles during the first postshock activation cycle. Purkinje activations were identified during the first and subsequent several postshock activation cycles in at least one basket and one needle electrogram in 96% and 98% of defibrillation episodes, respectively.
  
  
  CONCLUSIONS
  The Purkinje system is active during the early postshock activation cycles after DFT-level shocks. Further studies are required to determine whether activation initiates in the Purkinje system or whether it is activated by the myocardium or by Purkinje-myocardial junctional cells.
authors.affiliation: Department of Biomedical Engineering, University of Alabama at Birmingham, Birmingham, Alabama, USA.
authors.forename: Derek J
authors.initials: DJ
authors.lastname: Dosdall
authors.forename: Kang-An
authors.initials: KA
authors.lastname: Cheng
authors.forename: Jian
authors.initials: J
authors.lastname: Huang
authors.forename: J Scott
authors.initials: JS
authors.lastname: Allison
authors.forename: James D
authors.initials: JD
authors.lastname: Allred
authors.forename: William M
authors.initials: WM
authors.lastname: Smith
authors.forename: Raymond E
authors.initials: RE
authors.lastname: Ideker
mesh_terms: D000818:Animals; D018780:Body Surface Potential Mapping; D004554:Electric Countershock; D004566:Electrodes; D004699:Endocardium / Q000294:innervation*; D006329:Heart Conduction System / Q000503:physiopathology*; D006352:Heart Ventricles / Q000503:physiopathology*; D009206:Myocardium; D011690:Purkinje Fibers; D013552:Swine; D013997:Time Factors; D014693:Ventricular Fibrillation / Q000503:physiopathology*