title: Localizing the critical isthmus of postinfarct ventricular tachycardia: the value of pace-mapping during sinus rhythm.
abstract: BACKGROUND
  Most postinfarct ventricular tachycardias (VTs) are sustained by a reentrant mechanism. The "protected isthmus" of the reentrant circuit is critical for the maintenance of VTs and the target for catheter ablation. Various techniques based on conventional electrophysiology and/or detailed three-dimensional (3D) reconstruction of the VT circuit are used to unmask this isthmus.
  
  
  OBJECTIVE
  The purpose of this study was to assess pace-maps (PMs) to identify postinfarct VT isthmuses. We hypothesized that an abrupt change in paced QRS morphology may be used to identify a VT isthmus and be targeted for successful ablation.
  
  
  METHODS
  High-density 3D PMs were matched to the subsequent 3D endocardial reentrant VT activation mapping in 10 patients (8 men; age 70.7 ± 10.8 years) who underwent successful postinfarct VT ablation. At each pacing site in a given patient, the 12-lead ECG recorded during pacing was compared to that of VT, with the resulting matching percentage (up to 100% for perfect matches) allocated to this point to generate color-coded PMs.
  
  
  RESULTS
  With respect to VT isthmuses, the best percentages of matching were found in the exit zones and isthmus exit part (89% ± 8% and 84% ± 7%, respectively) and the poorest adjacent to scar border in the outer entrance zones (23% ± 28%), in the entrance zones (39% ± 34%), and in the entrance part of the isthmus (32% ± 26%). The color-coded sequence (from the best to the poorest matching sites) on the PMs revealed figure-of-eight pictures matching the VT activation time maps and identifying VT isthmuses.
  
  
  CONCLUSIONS
  Pace-mapping is useful for unmasking VT isthmuses in patients with well-tolerated postinfarct endocardial reentrant VTs.
authors: Christian
authors: C
authors: de Chillou
authors: Laurent
authors: L
authors: Groben
authors: Isabelle
authors: I
authors: Magnin-Poull
authors: Marius
authors: M
authors: Andronache
authors: Mohamed
authors: M
authors: MagdiAbbas
authors: Ning
authors: N
authors: Zhang
authors: Ahmed
authors: A
authors: Abdelaal
authors: Sonia
authors: S
authors: Ammar
authors: Jean-Marc
authors: JM
authors: Sellal
authors: Jérôme
authors: J
authors: Schwartz
authors: Béatrice
authors: B
authors: Brembilla-Perrot
authors: Etienne
authors: E
authors: Aliot
authors: Francis E
authors: FE
authors: Marchlinski
mesh_terms: D000368:Aged; D018780:Body Surface Potential Mapping; D004562:Electrocardiography; D055356:Endometrial Ablation Techniques; D005260:Female; D006801:Humans; D008297:Male; D009203:Myocardial Infarction / Q000150:complications*; D017180:Tachycardia, Ventricular / Q000209:etiology / Q000503:physiopathology*