title: Site-specific influence of transversal conduction across crista terminalis on recognition of isthmus block.
abstract: BACKGROUND
  Transversal conduction across crista terminalis (CT) is commonly observed during low-rate coronary sinus (CS) pacing after isthmus ablation and sometimes mimics incomplete clockwise isthmus block (IB). Site-specific influence of trans-cristal conduction gap on recognition of clockwise IB has been poorly understood.
  
  
  METHODS
  Forty-five patients with common-type atrial flutter underwent mapping of CT and free wall lateral to CT during CS pacing of 100 ppm using CARTO after verification of IB, while duodecapolar catheter was positioned along tricuspid annulus to map periannular activation.
  
  
  RESULTS
  A total of 43 gaps were demonstrated at upper (n = 15, 35%), middle (n = 17, 40%), and lower one-thirds of CT (n = 11, 25%) in 36 of 45 patients (80%). Gaps were single in 31 (69%) and multiple in 5 patients (11%). Activation patterns of free wall lateral to CT in CARTO maps were descending pattern without gaps (n = 9, 20%), collision pattern with a single gap (n = 31, 69%), and simultaneous pattern with multiple gaps (n = 5, 11%). Activation sequence of duodecapolar catheter was complete block pattern in 41 (91%) and incomplete block pattern in 4 patients (9%), masquerading as persistent clockwise isthmus conduction. The incomplete block pattern in duodecapolar catheter was exclusively associated with a gap at the lower CT (0/15, 0/17, and 4/11 gaps at upper, middle, and lower CT, respectively; P < 0.01) and was attributable to faster conduction across CT gaps than in complete block pattern.
  
  
  CONCLUSIONS
  Trans-cristal conduction was commonly observed during low-rate CS pacing. Rapid transversal conduction exclusively across lower CT masqueraded as incomplete clockwise IB.
authors.affiliation: Division of Cardiology, National Cardiovascular Center, Suita, Japan. k-otomo@fj8.so-net.ne.jp
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Otomo
authors.forename: Hideo
authors.initials: H
authors.lastname: Okamura
authors.forename: Takashi
authors.initials: T
authors.lastname: Noda
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Satomi
authors.forename: Wataru
authors.initials: W
authors.lastname: Shimizu
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Suyama
authors.forename: Takashi
authors.initials: T
authors.lastname: Kurita
authors.forename: Naohiko
authors.initials: N
authors.lastname: Aihara
authors.forename: Shiro
authors.initials: S
authors.lastname: Kamakura
mesh_terms: D001282:Atrial Flutter / Q000503:physiopathology* / Q000601:surgery; D017115:Catheter Ablation; D004594:Electrophysiology; D005260:Female; D006329:Heart Conduction System / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged