title: Noncontact mapping to guide ablation of right ventricular outflow tract tachycardia.
abstract: OBJECTIVE
  [corrected] The aim of this study was to determine whether noncontact mapping is feasible in the right ventricle and assess its utility in guiding ablation of difficult-to-treat right ventricular outflow tract (RVOT) ventricular tachycardia (VT).
  
  
  BACKGROUND
  In patients without inducible arrhythmia, RVOT VT may be difficult to ablate. Noncontact mapping permits ablation guided by a single tachycardia complex, which may facilitate ablation of difficult cases. However, the mapping system may be geometry-dependent, and it has not been validated in the unique geometry of the RVOT.
  
  
  METHODS
  Ten patients with left bundle inferior axis VT, no history of myocardial infarction and normal left ventricular function underwent noncontact guided ablation; seven had failed previous ablation and three had received a defibrillator. All noncontact maps were analyzed by a blinded reviewer to determine whether the arrhythmia focus was epicardial and to predict on the basis of the map whether arrhythmia would recur.
  
  
  RESULTS
  The procedure was acutely successful in 9 of 10 patients. During a mean follow-up of 11 months, 7 of 9 patients remained arrhythmia-free. Both patients in whom the blinded reviewer predicted failure had arrhythmia recurrence: one due to epicardial origin with multiple endocardial exit sites and one due to discordance between site of lesion placement and earliest activation on noncontact map.
  
  
  CONCLUSIONS
  Mechanisms of ablation failure in RVOT VT include absence of sustained arrhythmia, difficulty with substrate localization and epicardial origin of arrhythmia. In this study, noncontact mapping was safely and effectively used to guide ablation of patients with difficult-to-treat RVOT VT.
authors.affiliation: Division of Cardiovascular Disease, Mayo Clinic, 200 First Street SW, Rochester, MN 55905, USA. pfriedman@mayo.edu
authors.forename: Paul A
authors.initials: PA
authors.lastname: Friedman
authors.forename: Samuel J
authors.initials: SJ
authors.lastname: Asirvatham
authors.forename: Suellen
authors.initials: S
authors.lastname: Grice
authors.forename: Michael
authors.initials: M
authors.lastname: Glikson
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Munger
authors.forename: Robert F
authors.initials: RF
authors.lastname: Rea
authors.forename: Win K
authors.initials: WK
authors.lastname: Shen
authors.forename: Arshad
authors.initials: A
authors.lastname: Jahanghir
authors.forename: Douglas L
authors.initials: DL
authors.lastname: Packer
authors.forename: Stephen C
authors.initials: SC
authors.lastname: Hammill
mesh_terms: D000328:Adult; D018780:Body Surface Potential Mapping / Q000379:methods*; D017115:Catheter Ablation / Q000379:methods*; D022062:Electrophysiologic Techniques, Cardiac; D005260:Female; D005500:Follow-Up Studies; D006352:Heart Ventricles / Q000033:anatomy & histology / Q000503:physiopathology; D006801:Humans; D021621:Imaging, Three-Dimensional; D008297:Male; D008875:Middle Aged; D017180:Tachycardia, Ventricular / Q000601:surgery*; D017211:Treatment Failure