title: Change in size of lesions over 3 weeks after radiofrequency ablation of left ventricle.
abstract: BACKGROUND
  The initial success or failure of radiofrequency ablation (RFA) does not always reflect the long-term outcome that can lead to complications such as late atrioventricular block or recurrence of accessory pathways. We hypothesize that these occurrences may be due to a change in lesion size over time.
  
  
  RESULTS
  Intramural RFAs were performed on five greyhounds at thoracotomy using an epicardial approach into the left ventricular (LV) wall. Twenty-one gauge needle electrode ablations were created in the anterior aspect of the left ventricle. Radiofrequency energy was delivered at 600 Hz for 60 seconds and at an electrode temperature of 90 degrees C. Eight ablations were created in each greyhound and the chest was closed. After 3 weeks, a further eight ablations were created under the same conditions in the lateral aspect of the LV, ensuring they were well away from the chronic lesions, and the dogs were sacrificed an hour later. All lesions were removed, stained with Gomori Trichrome and measured. There was no significant difference in lesion size detected in the 1-hour-old lesions compared with 3-week-old lesions. Acute lesions were well demarcated by an area of fibrous scar and a central necrotic region. Chronic lesions showed chronic inflammatory cells and strands of collagen.
  
  
  CONCLUSIONS
  This study shows no change in lesion dimension over time and hence a change in size may not contribute to a change in RFA outcome over time.
authors.affiliation: Department of Cardiology, Westmead Hospital, University of Sydney, Westmead, NSW 2145, Australia. Kovoor@westgate.wh.usyd.edu.au
authors.forename: Pramesh
authors.initials: P
authors.lastname: Kovoor
authors.forename: Michael
authors.initials: M
authors.lastname: Daly
authors.forename: Michelle
authors.initials: M
authors.lastname: Mikhail
authors.forename: Vicki
authors.initials: V
authors.lastname: Eipper
authors.forename: Barbara
authors.initials: B
authors.lastname: Dewsnap
authors.forename: David L
authors.initials: DL
authors.lastname: Ross
mesh_terms: D000818:Animals; D017115:Catheter Ablation; D004195:Disease Models, Animal; D004285:Dogs; D005500:Follow-Up Studies; D006352:Heart Ventricles / Q000473:pathology* / Q000601:surgery; D017180:Tachycardia, Ventricular / Q000601:surgery*; D013997:Time Factors; D016896:Treatment Outcome