title: Quantitative comparison of spontaneous and paced 12-lead electrocardiogram during right ventricular outflow tract ventricular tachycardia.
abstract: OBJECTIVE
  The purpose of this study was to objectively quantify the similarity of 12-lead electrocardiogram (ECG) waveforms using two quantitative metrics, the correlation coefficient (CORR) and the mean absolute deviation (MAD).
  
  
  BACKGROUND
  Comparison of the 12-lead ECG morphology between ventricular tachycardia (VT) and a pace-map is frequently performed; however, there are no objective criteria for quantifying the similarity between two waveform morphologies.
  
  
  METHODS
  During ablation of right ventricular outflow tract (RVOT) VT, 12-lead ECG pace-maps were acquired from three superior septal sites, three superior free wall sites, and before each ablation attempt in 15 patients. The 12-lead ECG waveforms of the clinical tachycardia and pace-maps were compared using both MAD and CORR at each site.
  
  
  RESULTS
  The MAD scores were lower (i.e., more closely matched) for septal compared with free wall sites (15.9 +/- 5.3% vs. 25.3 +/- 10.2%; p < 0.001). Successful ablation sites had a significantly lower MAD score compared with unsuccessful sites (9.5 +/- 2.8% vs. 13.3 +/- 5.6%; p = 0.01), whereas there was only a trend toward a higher CORR for successful ablation sites (98.2 +/- 1.2% vs. 96 +/- 4.7%; p = 0.07). A MAD score < or =12% was 93% sensitive and 75% specific for identifying a successful ablation site. There was an inverse correlation between MAD score and distance from the site of VT origin (r = 0.63, p < 0.001).
  
  
  CONCLUSIONS
  A MAD score >12% between RVOT VT and a pace-map at any site suggests sufficient dissimilarity to dissuade ablation at that site. The MAD score can be used to standardize 12-lead ECG waveform morphology comparisons among different laboratories, and may be useful for guiding ablation of VT.
authors.affiliation: Division of Cardiology, Department of Internal Medicine, University of Pennsylvania Medical Center, 3400 Spruce Street, Philadelphia, PA 19104, USA. edward.gerstenfeld@uphs.upenn.edu
authors.forename: Edward P
authors.initials: EP
authors.lastname: Gerstenfeld
authors.forename: Sanjay
authors.initials: S
authors.lastname: Dixit
authors.forename: David J
authors.initials: DJ
authors.lastname: Callans
authors.forename: Yadavendra
authors.initials: Y
authors.lastname: Rajawat
authors.forename: Robert
authors.initials: R
authors.lastname: Rho
authors.forename: Francis E
authors.initials: FE
authors.lastname: Marchlinski
mesh_terms: D000328:Adult; D017115:Catheter Ablation; D004452:Echocardiography; D004562:Electrocardiography; D005260:Female; D006352:Heart Ventricles / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery; D006801:Humans; D008297:Male; D008875:Middle Aged; D010414:Pennsylvania; D011237:Predictive Value of Tests; D012680:Sensitivity and Specificity; D013223:Statistics as Topic; D017180:Tachycardia, Ventricular / Q000175:diagnosis* / Q000473:pathology* / Q000601:surgery; D016896:Treatment Outcome; D016277:Ventricular Function, Left / Q000502:physiology