title: Determinants of lesion dimensions during transcatheter microwave ablation.
abstract: BACKGROUND
  Transcatheter microwave ablation is a novel technique for treating cardiac arrhythmias.
  
  
  METHODS
  We investigated the effects of catheter temperature, application duration, and antenna length on lesion dimensions during catheter-based microwave ablation. In a swine thigh muscle preparation, microwave was delivered at targeted temperatures of 60 degrees C (n = 18), 70 degrees C (n = 27), 80 degrees C (n = 43), or 90 degrees C (n = 18) for 120 seconds with 10-mm antenna; and at targeted temperatures of 80 degrees C for 120 seconds (n = 22), 150 seconds (n = 18), 180 seconds (n = 18), 210 seconds (n = 18), and 240 seconds (n = 17) with 20-mm antenna using 10 F catheter (MedWaves, San Diego, CA, USA) during parallel orientation. Conventional radiofrequency ablation (RF) using a 4-mm tip electrode was performed as control.
  
  
  RESULTS
  With 120-second energy applications, lesion length and depth were significantly larger with targeted temperatures of 80 degrees C and 90 degrees C than 60 degrees C (P< 0.05). Furthermore, lesion depth and width, but not length, were significantly increased by prolonging energy application duration from 120 to 240 seconds at targeted temperature of 80 degrees C (P< 0.05). Compared to RF, microwave lesions were significantly longer but had comparable depth and width. A 20-mm microwave antenna produced longer lesions than either a 10-mm antenna or RF ablation catheter. Multivariate analysis demonstrated that targeted temperature >or=80 degrees C, application duration >or=150 seconds, and use of 20-mm antenna were independent predictors for lesion depth and width (P< 0.05). Surface dessication was observed in 4/18 (22%) lesions at 90 degrees C, as compared with 1/136 (0.7%) at 80 degrees C targeted tip temperature (P < 0.05).
  
  
  CONCLUSIONS
  This study demonstrated that lesions size with transcatheter microwave ablation can be controlled by adjusting targeted temperature, energy application duration, and antenna length. A targeted temperature of 80 degrees C for more than 150 seconds should provide optimal lesion dimensions and lower risk of surface dessication or charring.
authors.affiliation: Department of Medicine, Cardiology Division, University of Hong Kong, Hong Kong, China. hftse@hkucc.hku.hk
authors.forename: Hung-Fat
authors.initials: HF
authors.lastname: Tse
authors.forename: Songyan
authors.initials: S
authors.lastname: Liao
authors.forename: Chung-Wah
authors.initials: CW
authors.lastname: Siu
authors.forename: Liu
authors.initials: L
authors.lastname: Yuan
authors.forename: John
authors.initials: J
authors.lastname: Nicholls
authors.forename: George
authors.initials: G
authors.lastname: Leung
authors.forename: Ted
authors.initials: T
authors.lastname: Ormsby
authors.forename: Gregory K
authors.initials: GK
authors.lastname: Feld
authors.forename: Chu-Pak
authors.initials: CP
authors.lastname: Lau
mesh_terms: D000818:Animals; D001831:Body Temperature; D017115:Catheter Ablation / Q000379:methods*; D005260:Female; D008872:Microwaves / Q000627:therapeutic use*; D018482:Muscle, Skeletal / Q000473:pathology* / Q000502:physiology / Q000601:surgery*; D013552:Swine