title: Accuracy of the unipolar electrogram for identification of the site of origin of ventricular activation.
abstract: BACKGROUND
  The purpose of this study was to determine the accuracy of the unipolar electrogram for identifying the earliest site of ventricular activation. The earliest site of ventricular activation may be identified with the unipolar electrogram by the absence of an R wave. However, the accuracy of this technique is unknown.
  
  
  RESULTS
  A single ventricular premature complex was induced mechanically at the tip of an electrode catheter to simulate a ventricular premature depolarization site of origin. Unipolar electrograms were recorded from the right ventricular septum at the tip electrode and at 2, 5, 8, and 11 mm from the electrode tip in 20 patients. No R waves were detected at the ventricular premature depolarization site of origin. R waves were detected in 4 of 20 patients (20%) at 2 mm from the tip electrode and 7 of 20 patients (35%) at 5, 8, and 11 mm from the tip electrode. An R wave was not observed at distances < or = 11 mm from the site of tachycardia origin in 13 of 20 patients (65%).
  
  
  CONCLUSIONS
  While an R wave in the unipolar electrogram can be seen as close as 2 mm from the site of impulse origin, the absence of an R wave as an indicator of the site of impulse origin in the right ventricle is highly inaccurate. Therefore, the absence of an R wave in the unipolar electrogram is unlikely to be an adequate guide for identification of an effective target site for ablation of right ventricular tachycardia.
authors.affiliation: Department of Internal Medicine, University of Michigan Medical Center, Ann Arbor 48109-0022, USA.
authors.forename: K C
authors.initials: KC
authors.lastname: Man
authors.forename: E G
authors.initials: EG
authors.lastname: Daoud
authors.forename: B P
authors.initials: BP
authors.lastname: Knight
authors.forename: M
authors.initials: M
authors.lastname: Bahu
authors.forename: R
authors.initials: R
authors.lastname: Weiss
authors.forename: A
authors.initials: A
authors.lastname: Zivin
authors.forename: S J
authors.initials: SJ
authors.lastname: Souza
authors.forename: R
authors.initials: R
authors.lastname: Goyal
authors.forename: S A
authors.initials: SA
authors.lastname: Strickberger
authors.forename: F
authors.initials: F
authors.lastname: Morady
mesh_terms: D000328:Adult; D000368:Aged; D017115:Catheter Ablation; D003951:Diagnostic Errors; D004562:Electrocardiography / Q000295:instrumentation / Q000379:methods*; D004566:Electrodes; D004594:Electrophysiology / Q000295:instrumentation / Q000379:methods; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010865:Pilot Projects; D018497:Ventricular Dysfunction, Right / Q000175:diagnosis / Q000601:surgery; D018879:Ventricular Premature Complexes / Q000175:diagnosis* / Q000601:surgery