title: Electrogram analysis and pacing are complimentary for recognition of abnormal conduction and far-field potentials during substrate mapping of infarct-related ventricular tachycardia.
abstract: BACKGROUND
  Mapping to identify scar-related ventricular tachycardia re-entry circuits during sinus rhythm focuses on sites with abnormal electrograms or pace-mapping findings of QRS morphology and long stimulus to QRS intervals. We hypothesized that (1) these methods do not necessarily identify the same sites and (2) some electrograms are far-field potentials that can be recognized by pacing.
  
  
  RESULTS
  From 12 patients with coronary disease and recurrent ventricular tachycardia undergoing catheter ablation, we retrospectively analyzed electrograms and pacing at 546 separate low bipolar voltage (<1.5 mV) sites. Electrograms were characterized as showing evidence of slow conduction if late potentials (56%) or fractionated potentials (76%) were present. Neither was present at (13%) sites. Pacing from the ablation catheter captured 70% of all electrograms. Higher bipolar voltage and fractionation were independent predictors for pace capture. There was a linear correlation between the stimulus to QRS duration during pacing and the lateness of a capturing electrogram (P<0.001), but electrogram and pacing markers of slow conduction were discordant at 40% of sites. Sites with far-field potentials, defined as those that remained visible and not captured by pacing stimuli, were identified at 48% of all pacing sites, especially in areas of low bipolar voltage and late potentials. Initial radiofrequency energy application rendered 74% of targeted sites electrically unexcitable.
  
  
  CONCLUSIONS
  Far-field potentials are common in scar areas. Combining analysis of electrogram characteristics and assessment of pace capture may refine identification of substrate targets for radiofrequency ablation.
authors.affiliation: From the Cardiac Arrhythmia Center, Cardiovascular Division, Brigham and Women's Hospital, Boston, MA.
authors.forename: Samuel H
authors.initials: SH
authors.lastname: Baldinger
authors.affiliation: From the Cardiac Arrhythmia Center, Cardiovascular Division, Brigham and Women's Hospital, Boston, MA.
authors.forename: Koichi
authors.initials: K
authors.lastname: Nagashima
authors.affiliation: From the Cardiac Arrhythmia Center, Cardiovascular Division, Brigham and Women's Hospital, Boston, MA.
authors.forename: Saurabh
authors.initials: S
authors.lastname: Kumar
authors.affiliation: From the Cardiac Arrhythmia Center, Cardiovascular Division, Brigham and Women's Hospital, Boston, MA.
authors.forename: Chirag R
authors.initials: CR
authors.lastname: Barbhaiya
authors.affiliation: From the Cardiac Arrhythmia Center, Cardiovascular Division, Brigham and Women's Hospital, Boston, MA.
authors.forename: Eue-Keun
authors.initials: EK
authors.lastname: Choi
authors.affiliation: From the Cardiac Arrhythmia Center, Cardiovascular Division, Brigham and Women's Hospital, Boston, MA.
authors.forename: Laurence M
authors.initials: LM
authors.lastname: Epstein
authors.affiliation: From the Cardiac Arrhythmia Center, Cardiovascular Division, Brigham and Women's Hospital, Boston, MA.
authors.forename: Gregory F
authors.initials: GF
authors.lastname: Michaud
authors.affiliation: From the Cardiac Arrhythmia Center, Cardiovascular Division, Brigham and Women's Hospital, Boston, MA.
authors.forename: Roy
authors.initials: R
authors.lastname: John
authors.affiliation: From the Cardiac Arrhythmia Center, Cardiovascular Division, Brigham and Women's Hospital, Boston, MA.
authors.forename: Usha B
authors.initials: UB
authors.lastname: Tedrow
authors.affiliation: From the Cardiac Arrhythmia Center, Cardiovascular Division, Brigham and Women's Hospital, Boston, MA. wstevenson@partners.org.
authors.forename: William G
authors.initials: WG
authors.lastname: Stevenson
mesh_terms: D000368:Aged; D002304:Cardiac Pacing, Artificial / Q000379:methods*; D017115:Catheter Ablation; D022062:Electrophysiologic Techniques, Cardiac / Q000379:methods*; D005260:Female; D005500:Follow-Up Studies; D006329:Heart Conduction System / Q000503:physiopathology* / Q000601:surgery; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000150:complications*; D012189:Retrospective Studies; D017180:Tachycardia, Ventricular / Q000209:etiology / Q000503:physiopathology* / Q000628:therapy; D016896:Treatment Outcome
keywords: catheter ablation; ischemic cardiomyopathy; substrate ablation; tachycardia; ventricular