title: Usefulness of unipolar electrograms to detect isthmus block after radiofrequency ablation of typical atrial flutter.
abstract: BACKGROUND
  RS morphology of the unipolar electrogram is associated with propagation of the wave front through the exploring electrode, whereas positive uniphasic (R) unipolar electrograms are characteristic of the end of activation.
  
  
  RESULTS
  Unipolar electrograms were recorded in 45 consecutive patients with atrial flutter who were undergoing radiofrequency ablation (RFA). Bidirectional cavotricuspid isthmus (CTI) block was achieved in 44 patients. The unipolar electrogram obtained before RFA at the low anterolateral right atrium during coronary sinus pacing changed from RS, rS, or QS to R or Rs in all patients after clockwise CTI block was obtained. The morphology of unipolar electrograms recorded close to the coronary sinus during pacing from the low anterolateral right atrium changed from RS or rS to R or Rs in all but 4 patients after counterclockwise CTI block. In the patient in whom CTI block was not achieved, the RS morphology of the unipolar electrogram remained unchanged. In 18 patients, the results of the RFA were assessed with only the unipolar electrogram. The unipolar electrogram correctly predicted 100% and 89% of the cases of clockwise and counterclockwise CTI block, respectively.
  
  
  CONCLUSIONS
  The creation of CTI block is associated with an easily detectable loss of negative components and development of an R or Rs pattern of the unipolar electrogram recorded close to the ablation line while pacing at the opposite side of the CTI.
authors: Department of Cardiology, Hospital General Universitario Gregorio Marañón, Madrid, Spain.
authors: J
authors: J
authors: Villacastin
authors: J
authors: J
authors: Almendral
authors: A
authors: A
authors: Arenal
authors: N P
authors: NP
authors: Castellano
authors: S
authors: S
authors: Gonzalez
authors: M
authors: M
authors: Ortiz
authors: J
authors: J
authors: García
authors: B
authors: B
authors: Vallbona
authors: J
authors: J
authors: Moreno
authors: J F
authors: JF
authors: Portales
authors: E G
authors: EG
authors: Torrecilla
mesh_terms: D000368:Aged; D001282:Atrial Flutter / Q000503:physiopathology* / Q000601:surgery; D017115:Catheter Ablation; D004562:Electrocardiography / Q000379:methods*; D005260:Female; D006329:Heart Conduction System / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies