title: Radiofrequency lesions produced by handheld temperature controlled probes for use in atrial fibrillation surgery.
abstract: OBJECTIVE
  Detailed analysis of the size and shape of lesions produced by handheld radiofrequency ablation devices at open heart surgery has not been reported previously.
  
  
  METHODS
  Radiofrequency lesions were made from the epicardial surface of the cardiac ventricles in open-chested dogs. The effects of electrode size, electrode temperature and duration of ablation were studied. In a second group of experiments simultaneous multielectrode ablation was performed on the ventricular epicardium after cold cardioplegia.
  
  
  RESULTS
  Using a single 12 x 2.5 mm electrode and a target temperature of 80 degrees C the lesion depth increased from 3.8+/-0.9 mm at 15 s, to 6.1+/-0.9 mm at 120 s (P=0.01). Increasing the target temperature from 70 to 90 degrees C (for 60 s) increased lesion depth from 5.0+/-1.2 to 5.6+/-1.7 mm (P=0.2). There was no difference in depth of lesions with the two electrode widths (4.0+/-0.5 mm (large) vs. 3.9+/-1.0 mm (small)). Lesions produced using the multielectrode probe (80 degrees C, 60 s) were 30-35 mm long with even penetration into the tissue. The mean depth of these lesions on microscopic sections was 3.9 mm. The mean width was 7.1 mm.
  
  
  CONCLUSIONS
  Handheld probes can be used to make deep linear lesions in the myocardium. Lesions expand rapidly and are wider than they are deep. A multielectrode ablation device allows rapid formation of linear lesions.
authors.affiliation: Department of Cardiology, Westmead Hospital, Westmead, NSW 2145, Australia. stuartpt@yahoo.com
authors.forename: S P
authors.initials: SP
authors.lastname: Thomas
authors.forename: I A
authors.initials: IA
authors.lastname: Nicholson
authors.forename: G R
authors.initials: GR
authors.lastname: Nunn
authors.forename: D L
authors.initials: DL
authors.lastname: Ross
mesh_terms: D000818:Animals; D001281:Atrial Fibrillation / Q000601:surgery*; D017115:Catheter Ablation / Q000295:instrumentation / Q000379:methods*; D004285:Dogs; D004566:Electrodes; D009206:Myocardium / Q000473:pathology*; D013696:Temperature