title: Simple method of counterclockwise isthmus conduction block by comparing double potentials and flutter cycle length.
abstract: OBJECTIVE
  Local wide split double potentials are used as a parameter to determine complete conduction block during cavotricuspid isthmus ablation in patients with isthmus dependent atrial flutter. However, delayed slow conduction in that region can sometimes be very difficult to differentiate from complete block. Flutter cycle length (FCL) can be used to confirm isthmus conduction block, because FCL is a measure of conduction time around the tricuspid annulus (TA). This study was designed to determine which degree of splitting of the local electrograms is adequate to confirm complete isthmus block, using FCL as a reference.
  
  
  METHODS
  Cavotricuspid isthmus (CTI) ablation was performed in fifty consecutive patients. The interval between the pacing stimulus on the lateral side of the CTI and the first component of the double potentials on the block line (SD1) corresponded to the counterclockwise conduction time. The interval between the pacing stimulus and second component (SD2) represented the clockwise conduction time to the contralateral side of the ablation line. SD1 and SD2 were measured before and after complete isthmus block.
  
  
  RESULTS
  An SD1+SD2 reaching 90% of the FCL identified the counterclockwise isthmus conduction block with 94% sensitivity and 100% specificity.
  
  
  CONCLUSIONS
  If the sum of SD1 and SD2 following isthmus ablation was close to the FCL, complete conduction block was predicted with high diagnostic accuracy and positive predictive value for at least counterclockwise conduction.
authors.affiliation: Division of Cardiology, Department of Internal Medicine, Research Institute of Clinical Medicine, Chonbuk National University, Jeonju, Korea.
authors.forename: Kyoung-Suk
authors.initials: KS
authors.lastname: Rhee
authors.forename: Keun-Sang
authors.initials: KS
authors.lastname: Kwon
authors.forename: Sun Hwa
authors.initials: SH
authors.lastname: Lee
authors.forename: Kang-Hyu
authors.initials: KH
authors.lastname: Lee
authors.forename: Sang Rok
authors.initials: SR
authors.lastname: Lee
authors.forename: Jei Keon
authors.initials: JK
authors.lastname: Chae
authors.forename: Won-Ho
authors.initials: WH
authors.lastname: Kim
authors.forename: Jae-Ki
authors.initials: JK
authors.lastname: Ko
authors.forename: Gi-Byoung
authors.initials: GB
authors.lastname: Nam
authors.forename: Kee-Joon
authors.initials: KJ
authors.lastname: Choi
authors.forename: You-Ho
authors.initials: YH
authors.lastname: Kim