title: Recognition of far-field electrograms during entrainment mapping of ventricular tachycardia.
abstract: OBJECTIVE
  The goal of this study was to assess entrainment for distinguishing far-field potentials (FFP) due to depolarization of tissue at a distance from the mapping catheter from the local potential (LP) due to depolarization of tissue at the catheter electrode during mapping of ventricular tachycardia (VT).
  
  
  BACKGROUND
  Electrograms with multiple peaks commonly complicate mapping and identification of catheter ablation targets in infarcts.
  
  
  METHODS
  Retrospective analysis of catheter mapping data from eight patients with prior infarction was performed to evaluate multipotential electrograms at sites where pacing entrained VT. Potentials that were visible and not altered during pacing were defined as FFP. Potentials obscured by the pacing stimulus were designated possible LPs. The criteria for FFP were then assessed in a second cohort of five patients.
  
  
  RESULTS
  At 32 of 39 (82%) sites with multiple potentials, entrainment identified one of the potentials as an FFP. Radiofrequency ablation, assessed at 15 sites, reduced the amplitude of LPs by 62%, without significant effect on FFP amplitude. At 56% of sites with multiple potentials, measuring the postpacing interval to an FFP would lead to erroneous classification of the site location relative to the reentry circuit. In prospective evaluation, double potentials were identified at 77 sites in infarcts; entrainment demonstrated an FFP at 66 (86%) sites.
  
  
  CONCLUSIONS
  Far-field potentials are common during mapping in infarcts. Many can be distinguished from local potentials by entrainment, improving the accuracy of mapping.
authors.affiliation: Cardiovascular Division, Department of Internal Medicine, Brigham and Women's Hospital, Harvard Medical School, 75 Francis Street, Boston, MA 02115, USA.
authors.forename: Stanley
authors.initials: S
authors.lastname: Tung
authors.forename: Kyoko
authors.initials: K
authors.lastname: Soejima
authors.forename: William H
authors.initials: WH
authors.lastname: Maisel
authors.forename: Makoto
authors.initials: M
authors.lastname: Suzuki
authors.forename: Laurence
authors.initials: L
authors.lastname: Epstein
authors.forename: William G
authors.initials: WG
authors.lastname: Stevenson
mesh_terms: D000368:Aged; D017115:Catheter Ablation; D004562:Electrocardiography; D022062:Electrophysiologic Techniques, Cardiac; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D017180:Tachycardia, Ventricular / Q000175:diagnosis* / Q000503:physiopathology / Q000601:surgery