title: Effectiveness of two radiofrequency ablation systems in atrial tissue.
abstract: OBJECTIVE
  The efficacy of the left atrial radiofrequency ablation procedure, for the curative treatment of atrial fibrillation, is dependent upon obtaining a confluent transmural line of hyperthermic cellular death. We compare the in vitro effectiveness of obtaining transmural hyperthermic cellular death (>55 degrees C) of both the Osypka single electrode and Boston Scientific Thermaline multi-electrode radiofrequency systems.
  
  
  METHODS
  Isolated cadaver porcine hearts were used to measure epicardial temperatures either 'central' or at the 'edge' in relation to an endocardial applied radiofrequency electrode. Reference set point was 70 degrees C, and 4-6-mm thick atrial tissue was used for all applications. 'Edge' temperatures with the Boston Scientific unit were measured whilst activating both adjacent electrodes.
  
  
  RESULTS
  Boston Scientific: Probe temperature closely approximated the set point. 'Central' epicardial temperature was lower than probe temperature until after 40 s application (P<0.05), 55 degrees C was reached at 50 s, maximal mean temperature 63.0+/-8.9 degrees C was reached at 100 s. Epicardial 'edge' temperature remained lower than probe temperature for the entire 120 s (P<0.05). Osypka: Probe temperature tended to overshoot the set point. 'Central' epicardial temperature paralleled and occasionally exceeded probe temperature reaching 55 degrees C within 10 s, maximal mean temperature 76.3+/-12.7 degrees C was reached at 10 s and exceeded the set point thereafter. 'Edge' temperature was no different to probe temperature or 'central' epicardial temperature. The mean epicardial temperatures produced with a 65 degrees C set point was no different to that with the 70 degrees C set point, except for a lower final temperature at 60 s.
  
  
  CONCLUSIONS
  The Boston Scientific system (70 degrees C set point) requires a minimum in vitro application of 40 s to transmurally increase 4-6 mm atrial tissue temperature above 55 degrees C, and 120-s duration per application would appear to be a reasonable clinical recommendation. The Osypka system transfers thermal energy more effectively, requiring less than 10 s in vitro to achieve a similar transmural temperature, and a 30-s application can be recommended. However, a tendency to overshoot both probe and set point temperature, suggests that a lower set point of 65 degrees C might be safer and as effective.
authors.affiliation: Department of Cardiothoracic Surgery, University of Cape Town, 7925, Cape Town, South Africa. uvonopp@thoracic.cts.uct.ac.za
authors.forename: U O
authors.initials: UO
authors.lastname: von Oppell
authors.forename: T
authors.initials: T
authors.lastname: Rauch
authors.forename: G
authors.initials: G
authors.lastname: Hindricks
authors.forename: H
authors.initials: H
authors.lastname: Kottkamp
authors.forename: F
authors.initials: F
authors.lastname: Mohr
mesh_terms: D000818:Animals; D017115:Catheter Ablation / Q000295:instrumentation*; D066298:In Vitro Techniques; D013552:Swine; D013696:Temperature