title: Impact of duration of cryothermal application on clinical efficacy of pulmonary vein isolation using transvenous cryoablation.
abstract: BACKGROUND
  Recent studies have demonstrated that transvenous cryoablation is a safe and feasible method for pulmonary vein (PV) isolation for treatment of atrial fibrillation (AF). However, this technique is limited by a much longer ablation time than conventional radiofrequency ablation. The aim of this study was to determine the effect of duration of cryoablation application with double freeze-thaw cycles on clinical efficacy for PV isolation for treatment of AF.
  
  
  RESULTS
  We compared the clinical efficacy and procedural time of cryoablation (CryoCorTM, San Diego, CA, USA) for segmental PV isolation in 30 patients (mean age 51 +/- 13, 20 men) with paroxysmal AF using either double 5-minute (n = 15) or double 2.5-minute (n = 15) freeze-thaw cycle delivered with a 10 F deflectable transvenous catheter. Clinical recurrence of AF and the occurrence of PV stenosis as determined by computer tomography of the thorax were performed at 3- and 12-month follow-up. Acute successful electrical isolation of PV was achieved with cryoablation in 96 of 98 (98%) targeted PVs in 30 patients (mean: 3.2 +/- 0.8 PVs per patient). There were no significant differences between the baseline characteristics, the number of PV isolated per patient, the total number and percentage of effective cryoablation and the acute clinical efficacy between using double 5-minute and double 2.5-minute freezes (P > 0.05). However, the fluoroscopy time (107 +/- 43 vs 138 +/- 113 minutes, P = 0.06) and the procedural time (360 +/- 113 vs 510 +/- 115 minutes, P = 0.01) of using double 2.5-minute freezes was reduced by approximately 30% compared with double 5-minute freezes. At a mean of 20 +/- 8 month follow-up, there was no significant difference in the chronic clinical efficacy of cryoablation in terms of freedom from AF in the absence of antiarrhythmic drug therapy between using double 5-minute (6/15, 40%) and double 2.5-minute freezes (7/15, 46%, P = 0.98).
  
  
  CONCLUSIONS
  As compared with double 5-minute freeze, the use of a shorter double 2.5-minute freeze protocol significantly reduces the procedural time without affecting the acute and long-term clinical efficacy of cryoablation to isolate PV for treatment of AF.
authors.affiliation: Cardiology Division, Department of Medicine, The University of Hong Kong, Queen Mary Hospital, Hong Kong. hftes@hkucc.hku.hk
authors.forename: Hung-Fat
authors.initials: HF
authors.lastname: Tse
authors.forename: Chu-Pak
authors.initials: CP
authors.lastname: Lau
mesh_terms: D000328:Adult; D000368:Aged; D000704:Analysis of Variance; D001281:Atrial Fibrillation / Q000601:surgery*; D016009:Chi-Square Distribution; D003452:Cryosurgery / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011183:Postoperative Complications; D011667:Pulmonary Veins / Q000601:surgery*; D013997:Time Factors; D036542:Tomography, Spiral Computed; D016896:Treatment Outcome