title: A novel hybrid transcatheter ablation system that combines radiofrequency and cryoenergy.
abstract: BACKGROUND
  Radiofrequency (RF) and cryoenergy are largely considered independent modalities for the transcatheter ablation of cardiac arrhythmias. There are numerous theoretical advantages to engineering a system capable of delivering both energy forms.
  
  
  RESULTS
  We designed a hybrid steerable catheter capable of delivering RF and cryoenergy independently, sequentially, and simultaneously. The novel catheter system was tested pre-clinically by creating a total of 180 ablation lesions in 20 mongrel dogs. Right atrial and right and left ventricular sites were preselected by a randomized factorial design devised to compare sequential and simultaneous RF and cryoenergy applications to standard RF, irrigated RF, and standard cryoablation. A steerable 4-mm electrode-tip hybrid catheter ("Fire and Ice") was created by modifying a 7 F cryocatheter (Freezor, CryoCath Technologies, Montreal, Canada). RF energy was injected via a copper wire, thermocouples were isolated to reduce RF interference, and 100 KHz band pass filters and RF chokes were added. Sequential low-dose RF (20 W, 60 seconds) preceding or following cryoablation resulted in larger lesions (P = 0.0010). The addition of RF energy did, however, produce more thrombus than cryoenergy alone, with clot detected on 82.4% versus 12.1% of ablation lesions, P < 0.0001. Simultaneously applying the two energy modalities (45 W, 10 or 30 degrees C, 60 seconds) created more voluminous lesions than standard RF ablation (median 288.1 vs 126.1 mm(3), P = 0.0333) of similar dimension to irrigated RF ablation.
  
  
  CONCLUSIONS
  A versatile catheter system was fashioned capable of creating standard cryoablation lesions, standard RF lesions, and simultaneous lesions of similar dimension to irrigated RF.
authors.affiliation: Department of Medicine and Research Center, Montreal Heart Institute, Montreal, Canada. paul.khairy@umontreal.ca
authors.forename: Paul
authors.initials: P
authors.lastname: Khairy
authors.forename: Catherine
authors.initials: C
authors.lastname: Cartier
authors.forename: Patrick
authors.initials: P
authors.lastname: Chauvet
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Tanguay
authors.forename: Bertin
authors.initials: B
authors.lastname: Siméon
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Lalonde
authors.forename: Marc
authors.initials: M
authors.lastname: Dubuc
mesh_terms: D000818:Animals; D017115:Catheter Ablation / Q000295:instrumentation / Q000379:methods* / Q000639:trends; D003452:Cryosurgery / Q000295:instrumentation / Q000379:methods* / Q000639:trends; D004285:Dogs; D004867:Equipment Design / Q000295:instrumentation / Q000379:methods / Q000639:trends; D009206:Myocardium / Q000473:pathology