title: Creating bidirectional conduction block in the cavotricuspid isthmus by cryothermal ablation with a short freeze time: Insight from the results with a 2-minute freeze cycle.
abstract: BACKGROUND
  Optimal freeze doses are unknown during cryothermal cavo-tricuspid isthmus (CTI) ablation. This study aimed to evaluate the feasibility of 2-minute freeze doses for CTI ablation.
  
  
  METHODS
  Forty-eight consecutive patients undergoing cryothermal CTI ablation following pulmonary vein isolation were enrolled. CTI ablation was performed with 2-minute freeze cycles and 8-mm tip cryocatheters.
  
  
  RESULTS
  Bidirectional CTI block was successfully achieved in 45(93.8%) patients with a median of 5.0[4.0-6.0] cryocatheter applications. The total procedure and fluoroscopic times were a median of 16.5[13.0-20.0] and 4.0[2.0-5.0]min, respectively. A crossover to radiofrequency was performed in 3 patients including 1 due to coronary spasms during the cryoapplication. The tip temperature when block was achieved was a median of -81.0[-73.3 - -84.0]°C. Application times from the start of the last application to achieving block were significantly longer in patients with acute conduction resumption than in those without (46.8±4.0 vs. 20.2±8.8s, p<0.0001), and the optimal cutoff point for predicting no acute resumption was 38.5s (sensitivity 100%, specificity 99.5%). Vasospastic angina occurred in 2 patients, during the procedure in 1 and after in another. Durability could be evaluated a median of 6.0[3.0-8.0] months after the procedure in 14 patients, and conduction resumption was observed in 8(57.1%). The majority of gaps were located at the inferior vena cava edge.
  
  
  CONCLUSIONS
  Acute CTI block was obtained by 2-minute freeze cycles with short procedure and fluoroscopic times. Care should be taken to avoid coronary spasms during the peri-procedural period. Additional cryoapplications might be required to improve conduction block durability.
authors.affiliation: Cardiovascular Center, Tsuchiura Kyodo Hospital, Tsuchiura, Ibaraki, Japan. Electronic address: mshinsuke@k3.dion.ne.jp.
authors.forename: Shinsuke
authors.initials: S
authors.lastname: Miyazaki
authors.affiliation: Cardiovascular Center, Tsuchiura Kyodo Hospital, Tsuchiura, Ibaraki, Japan.
authors.forename: Jin
authors.initials: J
authors.lastname: Iwasawa
authors.affiliation: Cardiovascular Center, Tsuchiura Kyodo Hospital, Tsuchiura, Ibaraki, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Taniguchi
authors.affiliation: Cardiovascular Center, Tsuchiura Kyodo Hospital, Tsuchiura, Ibaraki, Japan.
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Nakamura
authors.affiliation: Cardiovascular Center, Tsuchiura Kyodo Hospital, Tsuchiura, Ibaraki, Japan.
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Hachiya
authors.affiliation: Cardiovascular Center, Tsuchiura Kyodo Hospital, Tsuchiura, Ibaraki, Japan.
authors.forename: Junji
authors.initials: J
authors.lastname: Matsuda
authors.affiliation: Cardiovascular Center, Tsuchiura Kyodo Hospital, Tsuchiura, Ibaraki, Japan.
authors.forename: Takamitsu
authors.initials: T
authors.lastname: Takagi
authors.affiliation: Cardiovascular Center, Tsuchiura Kyodo Hospital, Tsuchiura, Ibaraki, Japan.
authors.forename: Tomonori
authors.initials: T
authors.lastname: Watanabe
authors.affiliation: Heart Rhythm Center, Tokyo Medical and Dental University, Tokyo, Japan.
authors.forename: Kenzo
authors.initials: K
authors.lastname: Hirao
authors.affiliation: Cardiovascular Center, Tsuchiura Kyodo Hospital, Tsuchiura, Ibaraki, Japan.
authors.forename: Yoshito
authors.initials: Y
authors.lastname: Iesaka
mesh_terms: D000368:Aged; D001282:Atrial Flutter / Q000175:diagnosis / Q000503:physiopathology / Q000601:surgery*; D003452:Cryosurgery / Q000379:methods*; D004562:Electrocardiography / Q000379:methods; D005260:Female; D006329:Heart Conduction System / Q000503:physiopathology / Q000601:surgery*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011667:Pulmonary Veins / Q000601:surgery; D013997:Time Factors; D016896:Treatment Outcome
keywords: Atrial flutter; Cavo-tricuspid isthmus; Cryoablation; Freeze cycle; Vasospastic angina