title: Initial impedance decrease as an indicator of good catheter contact: insights from radiofrequency ablation with force sensing catheters.
abstract: BACKGROUND
  Good catheter-tissue contact force (CF) is critical for transmural and durable lesion formation during radiofrequency (RF) ablation but is difficult to assess in clinical practice. Tissue heating during RF application results in an impedance decrease at the catheter tip.
  
  
  OBJECTIVE
  The purpose of this study was to correlate achieved CF and initial impedance decreases during atrial fibrillation (AF) ablation.
  
  
  METHODS
  We correlated achieved CF and initial impedance decreases in patients undergoing ablation for AF with two novel open-irrigated CF-sensing RF catheters (Biosense Webster SmartTouch, n = 647 RF applications; and Endosense TactiCath, n = 637 RF applications). We then compared those impedance decreases to 691 RF applications with a standard open-irrigated RF catheter (Biosense Webster ThermoCool).
  
  
  RESULTS
  When RF applications with the CF-sensing catheters were analyzed according to an achieved average CF <5 g, 5-10 g, 10-20 g, and >20 g, the initial impedance decreases during ablation were larger with greater CF. Corresponding median values at 20 seconds were 5 Ω (interquartile range [IQR] 2-7), 8 Ω (4-11), 10 Ω (7-16), and 14 Ω (10-19) with the SmartTouch and n/a, 4 Ω (0-10), 8 Ω (5-12), and 13 Ω (8-18) with the TactiCath (P <.001 between categories for both catheters). When RF applications with the SmartTouch (CF-sensing catheter, median achieved CF 12 g) and ThermoCool (standard catheter) were compared, the initial impedance decrease was significantly greater in the CF-sensing group with median decreases of 10 Ω (6-14 Ω) vs 5 Ω (2-10 Ω) at 20 seconds (P <.001 between catheters).
  
  
  CONCLUSIONS
  The initial impedance decrease during RF applications in AF ablations is larger when greater catheter contact is achieved. Monitoring of the initial impedance decrease is a widely available indicator of catheter contact and may help to improve formation of durable ablation lesions.
authors.affiliation: Cardiovascular Division, Brigham and Women's Hospital, Boston, Massachusetts; University Hospital, Basel, Switzerland. Electronic address: treichlin@uhbs.ch.
authors.forename: Tobias
authors.initials: T
authors.lastname: Reichlin
authors.affiliation: University Hospital, Basel, Switzerland.
authors.forename: Sven
authors.initials: S
authors.lastname: Knecht
authors.affiliation: Cardiovascular Division, Brigham and Women's Hospital, Boston, Massachusetts.
authors.forename: Christopher
authors.initials: C
authors.lastname: Lane
authors.affiliation: University Hospital, Basel, Switzerland.
authors.forename: Michael
authors.initials: M
authors.lastname: Kühne
authors.affiliation: Cardiovascular Division, Brigham and Women's Hospital, Boston, Massachusetts; Leviev Heart Center, Sheba Medical Center, Tel Hashomer, Israel.
authors.forename: Eyal
authors.initials: E
authors.lastname: Nof
authors.affiliation: Cardiovascular Division, Brigham and Women's Hospital, Boston, Massachusetts.
authors.forename: Nagesh
authors.initials: N
authors.lastname: Chopra
authors.affiliation: Cardiovascular Division, Brigham and Women's Hospital, Boston, Massachusetts.
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Tadros
authors.affiliation: Helmsley Electrophysiology Center, The Cardiovascular Institute, Mount Sinai School of Medicine, New York, New York.
authors.forename: Vivek Y
authors.initials: VY
authors.lastname: Reddy
authors.affiliation: University Hospital, Basel, Switzerland.
authors.forename: Beat
authors.initials: B
authors.lastname: Schaer
authors.affiliation: Cardiovascular Division, Brigham and Women's Hospital, Boston, Massachusetts.
authors.forename: Roy M
authors.initials: RM
authors.lastname: John
authors.affiliation: University Hospital, Basel, Switzerland.
authors.forename: Stefan
authors.initials: S
authors.lastname: Osswald
authors.affiliation: Cardiovascular Division, Brigham and Women's Hospital, Boston, Massachusetts.
authors.forename: William G
authors.initials: WG
authors.lastname: Stevenson
authors.affiliation: University Hospital, Basel, Switzerland.
authors.forename: Christian
authors.initials: C
authors.lastname: Sticherling
authors.affiliation: Cardiovascular Division, Brigham and Women's Hospital, Boston, Massachusetts.
authors.forename: Gregory F
authors.initials: GF
authors.lastname: Michaud
mesh_terms: D000368:Aged; D001281:Atrial Fibrillation / Q000601:surgery; D017115:Catheter Ablation / Q000295:instrumentation* / Q000379:methods*; D057785:Catheters; D004867:Equipment Design; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged
keywords: AF; Atrial fibrillation ablation; CF; Contact force sensing catheter; EGM; IQR; Impedance decrease; PV; PVI; RF; atrial fibrillation; contact force; electrogram; interquartile range; pulmonary vein; pulmonary vein isolation; radiofrequency