title: Evaluation of the surface ECG in detecting isthmus conduction block after ablation of typical atrial flutter.
abstract: OBJECTIVE
  To investigate the value of changes in P wave morphology and duration detected by surface electrocardiogram (ECG) during proximal coronary sinus (PCS) and low lateral right atrial (LLRA) stimulation as a marker for complete bidirectional isthmus conduction block in the procedure of typical atrial flutter ablation.
  
  
  METHODS
  Morphology, duration, and ratio of a positive terminal P wave were estimated in 52 typical atrial flutter patients before and after radiofrequency catheter ablation (RFCA).
  
  
  RESULTS
  Atrial flutter ablation resulted in a complete bidirectional isthmus block in all 52 patients. The terminal portion of the P wave towards a positive morphology was detected in 90.7% (47/52) patients both during PCS and LLRA stimulation. These changes were predominantly observed in the inferior leads. Positive morphological changes of the terminal P wave portion and the measured P wave ratio (40% +/- 12%) in the inferior leads indicating bidirectional isthmus conduction block with a sensitivity of 87.5% and a specificity of 91.7% were observed. An increment of 20 ms or more in P wave duration during the PCS stimulation and 10 ms or more during the LLRA stimulation indicating the conduction block with a sensitivity of 90% and a specificity of 100%.
  
  
  CONCLUSIONS
  The variation of P wave morphology and duration in inferior leads of the surface ECG is a helpful technique to assess the complete bidirectional isthmus conduction block in the procedure of typical atrial flutter ablation.
authors.affiliation: Department of Cardiology, Qianfoshan Hospital of Shandong Province, Jinan, Shandong, China. yansuhua5537@163.com
authors.forename: Su-hua
authors.initials: SH
authors.lastname: Yan
authors.forename: Wen-juan
authors.initials: WJ
authors.lastname: Cheng
authors.forename: Ming-you
authors.initials: MY
authors.lastname: Chen
authors.forename: Mei
authors.initials: M
authors.lastname: Xue
authors.forename: He-sheng
authors.initials: HS
authors.lastname: Hu
mesh_terms: D001282:Atrial Flutter / Q000503:physiopathology / Q000601:surgery*; D017115:Catheter Ablation; D016009:Chi-Square Distribution; D004562:Electrocardiography; D005260:Female; D006327:Heart Block / Q000175:diagnosis* / Q000503:physiopathology; D006329:Heart Conduction System / Q000503:physiopathology* / Q000601:surgery; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012680:Sensitivity and Specificity; D016896:Treatment Outcome