title: Circuit Impedance Could Be a Crucial Factor Influencing Radiofrequency Ablation Efficacy and Safety: A Myocardial Phantom Study of the Problem and its Correction.
abstract: BACKGROUND
  Circuit impedance could affect the safety and efficacy of radiofrequency (RF) ablation.
  
  
  OBJECTIVE
  To perform irrigated RF ablations with graded impedance to compare (1) lesion dimensions and overheated dimensions in fixed power ablations (2) and in power corrected ablations.
  
  
  METHODS
  Ablations were performed with irrigated Navistar Thermocool catheter and Stockert EP shuttle generator at settings of 40 W power for 60 seconds, in a previously validated myocardial phantom. The impedance of the circuit was set at 60 Ω, 80 Ω, 100 Ω, 120 Ω, 140 Ω, and 160 Ω. The lesion and overheated dimensions were measured at 53 °C and 80 °C isotherms, respectively. In the second set of ablations, power was corrected according to circuit impedance.
  
  
  RESULTS
  In total, 70 ablations were performed. The lesion volume was 72.0 ± 4.8% and 44.7 ± 4.6% higher at 80 Ω and 100 Ω, respectively, compared to that at 120 Ω and it was 15.4 ± 1.2%, 28.1 ± 2.0%, and 38.0 ± 1.8% lower at 140 Ω, 160 Ω, and 180 Ω, respectively. The overheated volume was four times larger when impedance was reduced to 80 Ω from 100 Ω. It was absent at 120 Ω and above. In the power corrected ablations, the lesion volumes were similar to that of 40 W/120 Ω ablations and there was no evidence of overheating.
  
  
  CONCLUSIONS
  The lesion and overheated dimensions were significantly larger with lower circuit impedance during irrigated RF ablation and the lesion size was smaller in high impedance ablations. Power delivery adjusted to impedance using a simple equation improved the consistency of lesion formation and prevented overheating.
authors.affiliation: Cardiology Department, Westmead Hospital, Sydney, Australia.|Sydney Medical School, University of Sydney, Australia.
authors.forename: Abhishek
authors.initials: A
authors.lastname: Bhaskaran
authors.affiliation: Cardiology Department, Westmead Hospital, Sydney, Australia.|Sydney Medical School, University of Sydney, Australia.|School of Electrical and Information Engineering, University of Sydney, Australia.
authors.forename: M A
authors.initials: MA
authors.lastname: Barry
authors.affiliation: Cardiology Department, Westmead Hospital, Sydney, Australia.|Sydney Medical School, University of Sydney, Australia.
authors.forename: Jim
authors.initials: J
authors.lastname: Pouliopoulos
authors.affiliation: Cardiology Department, Westmead Hospital, Sydney, Australia.
authors.forename: Chrishan
authors.initials: C
authors.lastname: Nalliah
authors.affiliation: Cardiology Department, Westmead Hospital, Sydney, Australia.
authors.forename: Pierre
authors.initials: P
authors.lastname: Qian
authors.affiliation: Cardiology Department, Westmead Hospital, Sydney, Australia.|Sydney Medical School, University of Sydney, Australia.
authors.forename: William
authors.initials: W
authors.lastname: Chik
authors.affiliation: Cardiology Department, Westmead Hospital, Sydney, Australia.|Sydney Medical School, University of Sydney, Australia.
authors.forename: Sujitha
authors.initials: S
authors.lastname: Thavapalachandran
authors.affiliation: Cardiology Department, Westmead Hospital, Sydney, Australia.|Sydney Medical School, University of Sydney, Australia.
authors.forename: Lloyd
authors.initials: L
authors.lastname: Davis
authors.affiliation: School of Electrical and Information Engineering, University of Sydney, Australia.
authors.forename: Alistair
authors.initials: A
authors.lastname: McEwan
authors.affiliation: Cardiology Department, Westmead Hospital, Sydney, Australia.|Sydney Medical School, University of Sydney, Australia.
authors.forename: Stuart
authors.initials: S
authors.lastname: Thomas
authors.affiliation: Cardiology Department, Westmead Hospital, Sydney, Australia.|Sydney Medical School, University of Sydney, Australia.
authors.forename: Pramesh
authors.initials: P
authors.lastname: Kovoor
authors.affiliation: Cardiology Department, Westmead Hospital, Sydney, Australia.|Sydney Medical School, University of Sydney, Australia.
authors.forename: Aravinda
authors.initials: A
authors.lastname: Thiagalingam
mesh_terms: D017115:Catheter Ablation / Q000379:methods* / Q000592:standards; D017097:Electric Impedance; D004867:Equipment Design / Q000379:methods* / Q000592:standards; D009206:Myocardium; D019047:Phantoms, Imaging / Q000592:standards
keywords: circuit impedance; lesion dimensions; myocardial phantom; radiofrequency ablation; safety