title: Effect of limb lead electrodes location on ECG and localization of idiopathic outflow tract tachycardia: a prospective study.
abstract: BACKGROUND
  Different kinds of the surface ECG limb electrode positions may affect the limb lead vector and therefore the accuracy of the 12-lead ECG in localization of outflow tract ventricular tachycardia (OTVT). This study was intended to evaluate and compare the accuracy of the standard and the modified 12-lead ECG for localization of OTVT using the current published criteria.
  
  
  RESULTS
  Twenty consecutive patients (10 men, mean age, 51.6 ± 13.4 years) with OT-VT were included. A standard ECG with the distal placement of the limb lead electrodes and a modified ECG with the limb electrodes placed on the torso were recorded during the OT-VT and were used for localization by 2 electrophysiologists who were blinded to the successful ablation site to compare the accuracy of the 2 ECGs. The R wave amplitude during OT-VT in lead I of the standard 12-lead ECG was significantly higher compared to the modified surface ECG (0.225 ± 0.145 mV vs 0.139 ± 0.111 mV, P = 0.032). The S wave in aVR during OT-VT was significantly more negative compared to the modified surface ECG (-0.682 ± 0.182 mV vs -0.527 ± 0.228 mV, P = 0.017). The rate of accurate localization of the successful ablation sites in the anterior versus posterior outflow tract by the 2 observers using standard ECG (70% and 80%) were higher compared to modified ECG (50% and 60%, P = 0.042).
  
  
  CONCLUSIONS
  The R wave amplitude in lead I and the depth of the S wave amplitude in lead aVR of the standard surface ECG during OT-VT is significantly larger compared to the modified surface ECG. As the QRS morphology of the OT-VT is usually the first clue to the possible site of successful ablation, the standard 12-lead ECG should be used for more accurate localization of the origin of the OT-VT.
authors.affiliation: Department of Electrophysiology, University of Leipzig, Heart Center, Leipzig, Germany. dr.arasharya@gmail.com
authors.forename: Arash
authors.initials: A
authors.lastname: Arya
authors.forename: Yan
authors.initials: Y
authors.lastname: Huo
authors.forename: Fredrick
authors.initials: F
authors.lastname: Frogner
authors.forename: Ulrike
authors.initials: U
authors.lastname: Wetzel
authors.forename: Philipp
authors.initials: P
authors.lastname: Sommer
authors.forename: Thomas
authors.initials: T
authors.lastname: Gaspar
authors.forename: Sergio
authors.initials: S
authors.lastname: Richter
authors.forename: Christopher
authors.initials: C
authors.lastname: Piorkowski
authors.forename: Gerhard
authors.initials: G
authors.lastname: Hindricks
mesh_terms: D000328:Adult; D000368:Aged; D018780:Body Surface Potential Mapping / Q000295:instrumentation* / Q000379:methods; D004562:Electrocardiography / Q000295:instrumentation* / Q000379:methods; D004566:Electrodes; D005121:Extremities / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D017180:Tachycardia, Ventricular / Q000175:diagnosis / Q000503:physiopathology*; D014694:Ventricular Outflow Obstruction / Q000175:diagnosis / Q000503:physiopathology*