title: Temporal-component analysis of diastolic electrograms in ventricular tachycardia differentiates nonvulnerable regions of the circuit.
abstract: BACKGROUND
  Successful activation mapping of ventricular tachycardia (VT) is dependent on the identification of a region of diastolic conduction by use of point-by-point sequential mapping. It is important to identify the site of transition from diastolic conduction to systolic activation of healthy myocardium (exit site) and differentiate this from nonvulnerable regions of the circuit.
  
  
  OBJECTIVE
  We sought to determine the temporal and component characteristics of exit-site electrograms using simultaneous multielectrode endocardial mapping and to differentiate them from bystander sites during activation mapping.
  
  
  METHODS
  Sixteen VTs induced in 12 patients with ischemic cardiomyopathy who underwent multielectrode mapping during VT performed with a custom-made 112-bipolar-electrode endocardial array were analyzed retrospectively. The activation sequence in systole and diastole was annotated, and the timing at exit and bystander sites of the near-field component was characterized in relation to surface electrocardiogram activation and to the far-field component. Spectral content of bipolar electrograms recorded at these sites was additionally analyzed to identify the near-field to far-field interval.
  
  
  RESULTS
  The mean activation time at exit sites was 60.0 ± 31.5 ms (range 21-113 ms) ahead of surface QRS but was not significantly different from bystander sites (72.0 ± 55.0 ms, P = .63). However, the time delay from local to far-field activity was significantly lower at exit sites than at bystander sites (24.9 ± 15.6 vs. 86.6 ± 92.0 ms, P = .003), which was confirmed by spectral analysis (10.0 ± 13.1 vs. 89.0 ± 64.5 ms, P = .003).
  
  
  CONCLUSIONS
  Our analysis suggests that temporal-component analysis of diastolic electrograms during activation mapping of VT provides a practical method to differentiate nonvulnerable sites from the exit site without the need for pacing maneuvers.
authors.affiliation: Division of Cardiology, University Health Network, Toronto General Hospital, Toronto, Ontario, Canada.
authors.forename: Moloy
authors.initials: M
authors.lastname: Das
authors.affiliation: Division of Cardiology, University Health Network, Toronto General Hospital, Toronto, Ontario, Canada.
authors.forename: Eugene
authors.initials: E
authors.lastname: Downar
authors.affiliation: Division of Cardiology, University Health Network, Toronto General Hospital, Toronto, Ontario, Canada.
authors.forename: Stéphane
authors.initials: S
authors.lastname: Massé
authors.affiliation: Division of Cardiology, University Health Network, Toronto General Hospital, Toronto, Ontario, Canada.
authors.forename: Louise
authors.initials: L
authors.lastname: Harris
authors.affiliation: Division of Cardiology, University Health Network, Toronto General Hospital, Toronto, Ontario, Canada.
authors.forename: Doug
authors.initials: D
authors.lastname: Cameron
authors.affiliation: Division of Cardiology, University Health Network, Toronto General Hospital, Toronto, Ontario, Canada.
authors.forename: Krishnakumar
authors.initials: K
authors.lastname: Nair
authors.affiliation: Division of Cardiology, University Health Network, Toronto General Hospital, Toronto, Ontario, Canada.
authors.forename: Vijay S
authors.initials: VS
authors.lastname: Chauhan
authors.affiliation: Division of Cardiology, University Health Network, Toronto General Hospital, Toronto, Ontario, Canada.
authors.forename: Danna A
authors.initials: DA
authors.lastname: Spears
authors.affiliation: Division of Cardiology, University Health Network, Toronto General Hospital, Toronto, Ontario, Canada.
authors.forename: Andrew C
authors.initials: AC
authors.lastname: Ha
authors.affiliation: Division of Cardiology, University Health Network, Toronto General Hospital, Toronto, Ontario, Canada.
authors.forename: Nicholas
authors.initials: N
authors.lastname: Jackson
authors.affiliation: Division of Cardiology, University Health Network, Toronto General Hospital, Toronto, Ontario, Canada. Electronic address: k.nanthakumar@uhn.on.ca.
authors.forename: Kumaraswamy
authors.initials: K
authors.lastname: Nanthakumar
mesh_terms: D000328:Adult; D000368:Aged; D003971:Diastole; D004562:Electrocardiography / Q000295:instrumentation* / Q000379:methods*; D004566:Electrodes; D004699:Endocardium / Q000503:physiopathology*; D005260:Female; D006329:Heart Conduction System / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D013599:Systole; D017180:Tachycardia, Ventricular / Q000503:physiopathology*; D013997:Time Factors
keywords: Exit site; Ischemic cardiomyopathy; Multielectrode mapping; Ventricular tachycardia