title: Predictive value of impedance changes for real-time contact force measurements during catheter ablation of atrial arrhythmias in humans.
abstract: BACKGROUND
  Catheter-tissue contact force (CF) determines radiofrequency (RF) ablation lesion size. Impedance changes during RF delivery are used as surrogate markers for CF. The relationship between impedance and real-time CF in humans remains unknown.
  
  
  OBJECTIVE
  To determine whether impedance changes have predictive value for real-time CF during catheter ablation of atrial arrhythmias.
  
  
  METHODS
  Real-time CF, force-time integral, and impedance were measured in 2265 RF lesions for atrial fibrillation or flutter in 34 patients. Operators were blinded to CF measurements. Impedance preablation, at 5-second intervals for 30 seconds after the RF onset, maximal impedance fall and time to impedance plateau during RF were correlated with CF. Average CF was divided into low (≤20 g), intermediate (21-60 g), and high (>60 g) categories.
  
  
  RESULTS
  Preablation impedance poorly correlated with preablation CF (R = .07). Maximal impedance fall modestly correlated with average CF and force-time integral (R = .32 and .37, respectively). There was a large degree of overlap in impedance fall between different CF categories. A maximal impedance fall of 10 Ω could predict average CF of >20 g, with a sensitivity and specificity of 71% and 53% and a positive and negative predictive value of 51% and 49%, respectively. Impedance fall was only able to differentiate between different CF categories ≥15 seconds after the RF onset. Higher CFs moderately correlated with delayed plateau in impedance (R = .41).
  
  
  CONCLUSIONS
  Impedance measurements (both baseline and impedance fall) are, at best, moderately efficacious as surrogate markers for predicting real-time catheter-tissue CF. These findings highlight the importance of real-time CF measurements, rather than impedance changes to optimize ablation efficacy.
authors.affiliation: Department of Cardiology, The Royal Melbourne Hospital, Parkville, Victoria, Australia. jon. kalman@mh.org.au
authors.forename: Saurabh
authors.initials: S
authors.lastname: Kumar
authors.forename: H M
authors.initials: HM
authors.lastname: Haqqani
authors.forename: Martin
authors.initials: M
authors.lastname: Chan
authors.forename: Justin
authors.initials: J
authors.lastname: Lee
authors.forename: Matias
authors.initials: M
authors.lastname: Yudi
authors.forename: Michael C G
authors.initials: MC
authors.lastname: Wong
authors.forename: Joseph B
authors.initials: JB
authors.lastname: Morton
authors.forename: Liang-Han
authors.initials: LH
authors.lastname: Ling
authors.forename: Timothy
authors.initials: T
authors.lastname: Robinson
authors.forename: Patrick M
authors.initials: PM
authors.lastname: Heck
authors.forename: Nicholas F
authors.initials: NF
authors.lastname: Kelland
authors.forename: Karen
authors.initials: K
authors.lastname: Halloran
authors.forename: Steven J
authors.initials: SJ
authors.lastname: Spence
authors.forename: Peter M
authors.initials: PM
authors.lastname: Kistler
authors.forename: Jonathan M
authors.initials: JM
authors.lastname: Kalman
mesh_terms: D001281:Atrial Fibrillation / Q000503:physiopathology / Q000601:surgery*; D017115:Catheter Ablation / Q000379:methods*; D017097:Electric Impedance; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D016896:Treatment Outcome