title: Irrigated bipolar radiofrequency ablation with transmurality feedback for the surgical Cox-Maze procedure.
abstract: BACKGROUND
  Nonirrigated radiofrequency ablation (RFA) has been used to replicate the surgical scars of the Cox-Maze procedure. This study aimed to demonstrate that an irrigated, bipolar RFA energy source could also effectively replicate Cox-Maze lesions with impedance monitoring to predict the transmurality of ablated tissue.
  
  
  METHODS
  A complete Cox-Maze lesion pattern was created ex vivo on fresh porcine atria using an irrigated, bipolar RFA system. Tissues were clamped between opposing electrodes with steady pressure to ensure an intimate tissue-electrode interface during ablation. A proprietary feedback and control algorithm monitored tissue impedance and terminated ablation when lesions were deemed transmural by a plateau in impedance decline. Ablation time and power, lesion width and length, and tissue thickness were recorded. Lesions were stained with 1% triphenyltetrazolium chloride and sectioned for gross assessment of transmurality.
  
  
  RESULTS
  One hundred thirty-seven lesions were created on 11 porcine hearts. The total ablation time per lesion was 14.8 +/- 1.2 seconds (range, 10.0-19.0 seconds). Lesions averaged 4.2 +/- 1.3 mm (range, 1.3-10.2 mm) in width. Average tissue thickness was 3.0 +/- 1.7 mm (range, 0.5-9.9 mm). Crosssectional examination revealed that 100% of lesions were transmural (n = 718), and no tissue defects were observed.
  
  
  CONCLUSIONS
  These results indicate that irrigated bipolar RFA energy can produce transmural Cox-Maze lesions ex vivo on intact porcine atria and that impedance monitoring is a reliable predictor of lesion transmurality. Additional in vivo studies are under way to further demonstrate the efficacy and safety of irrigated, bipolar RFA technology.
authors.affiliation: Division of Cardiovascular Surgery, Mayo Clinic, Rochester, Minnesota 55905, USA. hammer.chad@mayo.edu
authors.forename: Chad E
authors.initials: CE
authors.lastname: Hamner
authors.forename: Alison
authors.initials: A
authors.lastname: Lutterman
authors.forename: D Dean
authors.initials: DD
authors.lastname: Potter
authors.forename: Thoralf M
authors.initials: TM
authors.lastname: Sundt
authors.forename: Hartzell V
authors.initials: HV
authors.lastname: Schaff
authors.forename: David
authors.initials: D
authors.lastname: Francischelli
mesh_terms: D000818:Animals; D001281:Atrial Fibrillation / Q000601:surgery*; D006348:Cardiac Surgical Procedures / Q000379:methods; D017115:Catheter Ablation / Q000009:adverse effects / Q000295:instrumentation / Q000379:methods*; D006325:Heart Atria / Q000601:surgery; D013552:Swine; D007507:Therapeutic Irrigation / Q000379:methods*