title: Focal Transcatheter Cryoablation: Is a Four-Minute Application Still Required?
abstract: BACKGROUND
  The standard 4-minute application time for transcatheter cryoablation was determined in the 1990s when the system employed less potent chlorofluorocarbon refrigerants. The current refrigerant, nitrous oxide, generates substantially colder temperatures, with a faster cooling rate.
  
  
  RESULTS
  We conducted a preclinical study on 32 mongrel dogs with stratified randomization of right atrial, right ventricular, and left ventricular chambers to 2-minute versus 4-minute application times using 8-mm electrode tip cryocatheters (Freezor Max, Medtronic CryoCath LP, Montreal, Canada). Animals were sacrificed one month after the procedure. Three-dimensional morphometric analyses were conducted in a blinded fashion. A total of 193 identified ablation lesions were processed for histological analyses, 102 with 2-minute applications and 91 with 4-minute applications. Ablation lesion surface area (167.8 ± 21.6 mm2vs. 194.3 ± 22.6 mm2, P = 0.40), maximum depth (4.4 ± 0.2 mm vs. 4.5 ± 0.2 mm, P = 0.71), and volume (125.7 ± 69.5 mm3vs. 141.0 ± 83.5 mm3, P = 0.25) were similar between groups. Overall, 90.2% of ablation lesions in the right atrium were transmural, 45.6% in the right ventricle, and 2.4% in the left ventricle, with no differences between 2-minute and 4-minute application times (P = 0.55). Thrombus was detected on the endocardial surface of 0.0% and 3.3% of ablation lesions created with 2-minute and 4-minute application times, respectively (P = 0.10).
  
  
  CONCLUSIONS
  Single 2-minute and 4-minute application times result in catheter ablation lesions of similar size using the modern cryoablation system with nitrous oxide as a refrigerant. While these findings suggest the potential to reduce the standard 4-minute application time, further studies are required to compare clinical efficacy.
authors.affiliation: Electrophysiology Service and Research Center, Montreal Heart Institute, Université de Montréal, Montreal, Canada.
authors.forename: Françis
authors.initials: F
authors.lastname: Bessière
authors.affiliation: Electrophysiology Service and Research Center, Montreal Heart Institute, Université de Montréal, Montreal, Canada.
authors.forename: Marc
authors.initials: M
authors.lastname: Dubuc
authors.affiliation: Electrophysiology Service and Research Center, Montreal Heart Institute, Université de Montréal, Montreal, Canada.
authors.forename: Jason
authors.initials: J
authors.lastname: Andrade
authors.affiliation: Montreal Health Innovations Coordinating Centre (MHICC), Université de Montréal, Montreal, Canada.
authors.forename: Azadeh
authors.initials: A
authors.lastname: Shohoudi
authors.affiliation: Electrophysiology Service and Research Center, Montreal Heart Institute, Université de Montréal, Montreal, Canada.
authors.forename: Martin G
authors.initials: MG
authors.lastname: Sirois
authors.affiliation: Electrophysiology Service and Research Center, Montreal Heart Institute, Université de Montréal, Montreal, Canada.
authors.forename: Blandine
authors.initials: B
authors.lastname: Mondésert
authors.affiliation: Electrophysiology Service and Research Center, Montreal Heart Institute, Université de Montréal, Montreal, Canada.
authors.forename: Katia
authors.initials: K
authors.lastname: Dyrda
authors.affiliation: Electrophysiology Service and Research Center, Montreal Heart Institute, Université de Montréal, Montreal, Canada.
authors.forename: Lena
authors.initials: L
authors.lastname: Rivard
authors.affiliation: Electrophysiology Service and Research Center, Montreal Heart Institute, Université de Montréal, Montreal, Canada.
authors.forename: Laurent
authors.initials: L
authors.lastname: Macle
authors.affiliation: Electrophysiology Service and Research Center, Montreal Heart Institute, Université de Montréal, Montreal, Canada.
authors.forename: Peter G
authors.initials: PG
authors.lastname: Guerra
authors.affiliation: Electrophysiology Service and Research Center, Montreal Heart Institute, Université de Montréal, Montreal, Canada.
authors.forename: Bernard
authors.initials: B
authors.lastname: Thibault
authors.affiliation: Electrophysiology Service and Research Center, Montreal Heart Institute, Université de Montréal, Montreal, Canada.
authors.forename: Mario
authors.initials: M
authors.lastname: Talajic
authors.affiliation: Electrophysiology Service and Research Center, Montreal Heart Institute, Université de Montréal, Montreal, Canada.
authors.forename: Denis
authors.initials: D
authors.lastname: Roy
authors.affiliation: Electrophysiology Service and Research Center, Montreal Heart Institute, Université de Montréal, Montreal, Canada.|Montreal Health Innovations Coordinating Centre (MHICC), Université de Montréal, Montreal, Canada.
authors.forename: Paul
authors.initials: P
authors.lastname: Khairy
mesh_terms: D000818:Animals; D006328:Cardiac Catheterization / Q000379:methods*; D003080:Cold Temperature; D003452:Cryosurgery / Q000379:methods*; D004285:Dogs; D006325:Heart Atria / Q000473:pathology / Q000601:surgery*; D006352:Heart Ventricles / Q000473:pathology / Q000601:surgery*; D023421:Models, Animal; D009609:Nitrous Oxide / Q000494:pharmacology*; D013997:Time Factors
chemical_list: D009609:Nitrous Oxide
keywords: catheter ablation; cryoablation; cryoenergy