title: ECG criteria for accurate localization of left anterolateral and posterolateral accessory pathways.
abstract: BACKGround : Left lateral accessory pathway (AP) location along the mitral annulus (MA) can influence ablation strategy, including choice of a transseptal or retrograde aortic approach and the use of deflectable sheaths and/or bidirectional catheters. We aimed to develop electrocardiographic (ECG) criteria to accurately localize a left lateral AP, hypothesizing that the relationship of QRS amplitudes in limb leads II and III could be used to differentiate left anterolateral (LAL) from left posterolateral (LPL) AP locations.
  
  
  METHODS
  The ECGs from patients who underwent ablation of a left-sided AP between 2001 and 2008 were evaluated for the relationship of QRS amplitudes in limb leads II and III. A LAL-AP was defined by successful ablation between 12 and 3 o'clock on the MA, as seen in left anterior oblique (LAO) fluoroscopic projection. A LPL-AP was defined by successful ablation between 3 and 6 o'clock in the LAO projection.
  
  
  RESULTS
  In 249 consecutive patients undergoing AP ablation, 23 met the prespecified inclusion criteria: manifest preexcitation due to single AP, ablated successfully in a LAL or LPL location. The ratio of dominant QRS amplitude in lead II to lead III was ≥ 1 in 10/11 patients with LAL-AP, compared with 3/12 patients with a LPL-AP (P = 0.002). Using these criteria, two blinded reviewers predicted a LAL or LPL location with 87% accuracy and 100% interobserver agreement.
  
  
  CONCLUSIONS
  We report new ECG criteria that can be used to accurately predict the anterior and posterior location of a left lateral AP. Such localization may facilitate procedural planning.
authors.affiliation: Department of Medicine, Section of Cardiology, University of Chicago, Chicago, Illinois 60614, USA. jmoss@bsd.uchicago.edu
authors.forename: Joshua D
authors.initials: JD
authors.lastname: Moss
authors.forename: Edward P
authors.initials: EP
authors.lastname: Gerstenfeld
authors.forename: Rajat
authors.initials: R
authors.lastname: Deo
authors.forename: Mathew D
authors.initials: MD
authors.lastname: Hutchinson
authors.forename: David J
authors.initials: DJ
authors.lastname: Callans
authors.forename: Francis E
authors.initials: FE
authors.lastname: Marchlinski
authors.forename: Sanjay
authors.initials: S
authors.lastname: Dixit
mesh_terms: D058606:Accessory Atrioventricular Bundle / Q000503:physiopathology* / Q000601:surgery*; D000465:Algorithms; D017115:Catheter Ablation; D004562:Electrocardiography; D005260:Female; D005471:Fluoroscopy; D006801:Humans; D008297:Male; D012372:ROC Curve; D016896:Treatment Outcome; D014927:Wolff-Parkinson-White Syndrome / Q000503:physiopathology* / Q000601:surgery*