title: Unipolar electrogram characteristics predictive of successful radiofrequency catheter ablation of accessory pathways.
abstract: BACKGROUND
  The purpose of this study was to determine the characteristics of the unipolar electrogram that are most helpful in predicting successful radiofrequency ablation of accessory pathways.
  
  
  RESULTS
  The unipolar electrogram was analyzed at 185 ablation sites in 53 patients; 94 attempts were directed at the site of earliest atrial activation ("atrial group") and 91 at the site of earliest ventricular activation ("ventricular group"). The electrogram was analyzed for several features, including pattern ("QS" or "initial R"). Unipolar pattern: Overall, a "QS" pattern was seen at 55% of unsuccessful, 75% of temporarily successful, and 90% of permanently successful sites. For the atrial group, the respective frequencies were 53%, 77%, and 92%, and for the ventricular group, 57%, 73%, and 86%. The difference in pattern distribution between unsuccessful and permanently successful sites was significant for all groups: overall, P < 0.0001; atrial group, P = 0.0005; ventricular group, P = 0.02. Absence of a "QS" pattern (i.e., "initial R") predicted a 92% chance of unsuccessful ablation. Additional features: Activation times were significantly shorter at permanently successful than at unsuccessful (P < 0.0001) or temporarily successful sites (P = 0.0002). No significant differences were found in atrial or ventricular amplitudes or in A/V ratios. Intrinsic deflection slew was lower at temporarily successful sites (P = 0.03 vs all other sites).
  
  
  CONCLUSIONS
  Ablation at sites revealing an "initial R" pattern (i.e., absent "QS") is very unlikely to be successful. Activation time is shorter at successful sites. These features are equally applicable when mapping the atrial potential as when mapping the ventricular potential.
authors.affiliation: Division of Cardiology, The University of Western Ontario, London, Canada.
authors.forename: M A
authors.initials: MA
authors.lastname: Barlow
authors.forename: G J
authors.initials: GJ
authors.lastname: Klein
authors.forename: C S
authors.initials: CS
authors.lastname: Simpson
authors.forename: F D
authors.initials: FD
authors.lastname: Murgatroyd
authors.forename: R
authors.initials: R
authors.lastname: Yee
authors.forename: A D
authors.initials: AD
authors.lastname: Krahn
authors.forename: A C
authors.initials: AC
authors.lastname: Skanes
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D016275:Atrial Function; D017115:Catheter Ablation; D002648:Child; D004562:Electrocardiography / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D013617:Tachycardia, Supraventricular / Q000503:physiopathology* / Q000601:surgery*; D016896:Treatment Outcome; D016276:Ventricular Function; D014927:Wolff-Parkinson-White Syndrome / Q000503:physiopathology* / Q000601:surgery*