title: Double potential interval and transisthmus conduction time for prediction of cavotricuspid isthmus block after ablation of typical atrial flutter.
abstract: BACKGROUND
  Complete bi-directional isthmus block is the endpoint of typical atrial flutter ablation. The purpose of this study was to investigate the feasibility of the local double potential (DP) interval and the change in transisthmus conduction time for predicting complete isthmus block after ablation of the cavotricuspid isthmus.
  
  
  METHODS
  The study population consisted of 32 patients with typical atrial flutter after a procedure of radiofrequency (RF) ablation of the cavotricuspid isthmus (16 had incomplete block and 16 had complete block). The transisthmus conduction time was determined during pacing from the proximal coronary sinus and low lateral right atrium before and after RF ablation. The DP interval close to the ablation line was evaluated after final RF energy application.
  
  
  RESULTS
  In the counterclockwise direction, transisthmus conduction time had an increase of 37 +/- 25.4% and 127.3 +/- 35.5% (P < 0.001), and the DP interval was 63.3 +/- 8.7 ms and 120 +/- 17.4 ms (P < 0.001) after achievement of incomplete and complete block, respectively. The sensitivity, specificity, positive and negative predictive values of an increase in the transisthmus conduction time > or =50% were 100%, 81%, 84% and 100%, respectively; those of DP interval > or =100 ms were 100%. In the clockwise direction, transisthmus conduction time had an increase of 38.8 +/- 28.6% and 135.7 +/- 63.6% (P < 0.001), and the DP interval was 63.6 +/- 13.8 ms and 127.7 +/- 27.1 ms (P < 0.001) after achievement of incomplete and complete block, respectively. The sensitivity, specificity, positive and negative predictive values of an increase in the transisthmus conduction time > or =50% were 100%, 67%, 83% and 100%, respectively; those of the DP interval > or =100 ms were 100%.
  
  
  CONCLUSIONS
  The transisthmus conduction time > or =50% increase or DP interval > or =100 ms was feasible to predict complete bi-directional isthmus block.
authors.affiliation: Division of Cardiology, Department of Medicine, National Yang-Ming University School of Medicine, Taipei Veterans General Hospital, Taiwan, ROC. cttai@vghtpe.gov.tw
authors.forename: Ching-Tai
authors.initials: CT
authors.lastname: Tai
authors.forename: Azizul
authors.initials: A
authors.lastname: Haque
authors.forename: Yung-Kuo
authors.initials: YK
authors.lastname: Lin
authors.forename: Hsuan-Ming
authors.initials: HM
authors.lastname: Tsao
authors.forename: Yu-An
authors.initials: YA
authors.lastname: Ding
authors.forename: Mau-Song
authors.initials: MS
authors.lastname: Chang
authors.forename: Shih-Ann
authors.initials: SA
authors.lastname: Chen
mesh_terms: D000200:Action Potentials; D000368:Aged; D001282:Atrial Flutter / Q000601:surgery*; D017115:Catheter Ablation / Q000379:methods*; D022062:Electrophysiologic Techniques, Cardiac / Q000379:methods*; D005240:Feasibility Studies; D005260:Female; D005500:Follow-Up Studies; D006327:Heart Block / Q000175:diagnosis* / Q000209:etiology* / Q000503:physiopathology; D006329:Heart Conduction System / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D012008:Recurrence; D012680:Sensitivity and Specificity; D013997:Time Factors; D016896:Treatment Outcome; D014261:Tricuspid Valve; D014684:Venae Cavae