title: Novel transitional zone index allows more accurate differentiation between idiopathic right ventricular outflow tract and aortic sinus cusp ventricular arrhythmias.
abstract: BACKGROUND
  Although several ECG algorithms have been proposed for differentiating the origins of outflow tract ventricular arrhythmia (OT-VA), their accuracy still is limited in cases with cardiac rotation.
  
  
  OBJECTIVE
  The purpose of this study was to assess whether a novel "cardiac rotation-corrected" transitional zone (TZ) index would be a useful marker for differentiating right ventricular outflow tract (RVOT) origin from aortic sinus cusp (ASC) origin.
  
  
  METHODS
  Surface ECGs of OT-VAs with left bundle branch block morphology and inferior axis in 112 patients who were successfully ablated in the RVOT (n = 87) or the ASC (n = 25) were analyzed. The TZ index was defined according to the site of R-wave transition of sinus beats and OT-VAs.
  
  
  RESULTS
  The TZ index was significantly lower in the ASC origin than in the RVOT origin (-1.2 ± 0.9 vs 0.3 ± 0.7, P <.0001). A cutoff value of the TZ index <0 predicted the ASC origin with 88% sensitivity and 82% specificity. The previously reported R-wave duration index ≥ 50% had a high specificity of 85% but a low sensitivity of 44%, and R/S-wave amplitude index ≥ 30% had 68% sensitivity and 79% specificity. The area under the curve by receiver operating characteristic curve analysis was 0.90 for the TZ index, which was significantly higher than the R-wave duration index and R/S-wave amplitude index of 0.74 and 0.76, respectively.
  
  
  CONCLUSIONS
  This novel TZ index can be a more useful marker for differentiating RVOT origin from ASC origin.
authors.affiliation: Department of Cardiology, Nagoya University Graduate School of Medicine, Nagoya, Japan.
authors.forename: Naoki
authors.initials: N
authors.lastname: Yoshida
authors.forename: Yasuya
authors.initials: Y
authors.lastname: Inden
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Uchikawa
authors.forename: Hiromi
authors.initials: H
authors.lastname: Kamiya
authors.forename: Kazuhisa
authors.initials: K
authors.lastname: Kitamura
authors.forename: Masayuki
authors.initials: M
authors.lastname: Shimano
authors.forename: Yukiomi
authors.initials: Y
authors.lastname: Tsuji
authors.forename: Makoto
authors.initials: M
authors.lastname: Hirai
authors.forename: Toyoaki
authors.initials: T
authors.lastname: Murohara
mesh_terms: D000368:Aged; D001146:Arrhythmia, Sinus / Q000601:surgery*; D018780:Body Surface Potential Mapping / Q000379:methods*; D017115:Catheter Ablation / Q000379:methods*; D005260:Female; D006329:Heart Conduction System / Q000503:physiopathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D012372:ROC Curve; D012680:Sensitivity and Specificity; D012850:Sinus of Valsalva; D014694:Ventricular Outflow Obstruction / Q000175:diagnosis / Q000503:physiopathology / Q000601:surgery*