title: Electrode radius predicts lesion radius during radiofrequency energy heating. Validation of a proposed thermodynamic model.
abstract: Myocardial heating by transcatheter delivery of radiofrequency (RF) energy has been proposed as an effective means of arrhythmia ablation. A thermodynamic model describing the radial temperature gradient at steady state during RF-induced heating is proposed. If one assumes that RF power output is adjusted to maintain a constant electrode-tissue interface temperature at all times, then this thermodynamic model predicts that the radius of the RF-induced lesion will be directly proportional to the electrode radius. A total of 76 RF-induced lesions were created in a model of isolated canine right ventricular free wall perfused and superfused with oxygenated Krebs-Henseleit buffer. Electrode radius was varied between 0.75 and 2.25 mm. RF energy (500 kHz) was delivered for 90 seconds, and the power output was adjusted to maintain a constant electrode-tissue interface temperature of 60 degrees C. A strong linear correlation was observed between electrode radius and lesion radius in two dimensions: transverse (p = 0.0001, r = 0.85) and transmural (p = 0.0001, r = 0.89). With these data, the temperature correlation with irreversible myocardial injury in this model was calculated at 46.6-48.8 degrees C. Therefore, the proposed thermodynamic model closely predicts the observed relation between electrode radius and lesion size during RF myocardial heating.
authors.affiliation: Department of Internal Medicine, University of Virginia, School of Medicine, Charlottesville.
authors.forename: D E
authors.initials: DE
authors.lastname: Haines
authors.forename: D D
authors.initials: DD
authors.lastname: Watson
authors.forename: A F
authors.initials: AF
authors.lastname: Verow
mesh_terms: D000818:Animals; D004285:Dogs; D004566:Electrodes; D005069:Evaluation Studies as Topic; D005544:Forecasting; D006321:Heart / Q000528:radiation effects*; D006358:Hot Temperature; D008962:Models, Theoretical; D009206:Myocardium / Q000473:pathology; D011846:Radio Waves; D013696:Temperature; D013816:Thermodynamics