title: Functional pace-mapping responses for identification of targets for catheter ablation of scar-mediated ventricular tachycardia.
abstract: BACKGROUND
  Myocardial scars harbor areas of slow conduction and display abnormal electrograms. Pace-mapping at these sites can generate a 12-lead ECG morphological match to a targeted ventricular tachycardia (VT), and in some instances, multiple exit morphologies can result. At times, this can also result in the initiation of VT, termed pace-mapped induction (PMI). We hypothesized that in patients undergoing catheter ablation of VT, scar substrates with multiple exit sites (MES) identified during pace-mapping have improved freedom from recurrent VT, and PMI of VT predicts successful sites of termination during ablation.
  
  
  RESULTS
  High-density mapping was performed in all subjects to delineate scar (0.5-1.5 mV). Sites with abnormal electrograms were tagged, stimulated (bipolar 10 mA at 2 ms), and targeted for ablation. MES was defined as >1 QRS morphology from a single pacing site. PMI was defined as initiation of VT during pace-mapping (400-600 ms). In a 2-year period, 44 consecutive patients with scar-mediated VT underwent mapping and ablation. MES were observed during pace-mapping in 25 patients (57%). At 9 months, 74% of patients who exhibited MES during pace-mapping had no recurrence of VT compared with 42% of those without MES observed (P=0.024), with an overall freedom from VT of 61%. Thirteen patients (30%) demonstrated PMI, and termination of VT was seen in 95% (18/19) of sites where ablation was performed.
  
  
  CONCLUSIONS
  During pace-mapping, electrograms that exhibit MES and PMI may be specific for sites critical to reentry. These functional responses hold promise for identifying important sites for catheter ablation of VT.
authors.affiliation: UCLA Cardiac Arrhythmia Center, UCLA Health System, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095-1679, USA. rtung@mednet.ucla.edu
authors.forename: Roderick
authors.initials: R
authors.lastname: Tung
authors.forename: Nilesh
authors.initials: N
authors.lastname: Mathuria
authors.forename: Yoav
authors.initials: Y
authors.lastname: Michowitz
authors.forename: Ricky
authors.initials: R
authors.lastname: Yu
authors.forename: Eric
authors.initials: E
authors.lastname: Buch
authors.forename: Jason
authors.initials: J
authors.lastname: Bradfield
authors.forename: Ravi
authors.initials: R
authors.lastname: Mandapati
authors.forename: Isaac
authors.initials: I
authors.lastname: Wiener
authors.forename: Noel
authors.initials: N
authors.lastname: Boyle
authors.forename: Kalyanam
authors.initials: K
authors.lastname: Shivkumar
mesh_terms: D000368:Aged; D017115:Catheter Ablation; D002921:Cicatrix / Q000150:complications*; D015331:Cohort Studies; D004562:Electrocardiography; D005260:Female; D006329:Heart Conduction System / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D012008:Recurrence; D012189:Retrospective Studies; D017180:Tachycardia, Ventricular / Q000209:etiology* / Q000503:physiopathology / Q000601:surgery*; D016896:Treatment Outcome