title: Effect of radiofrequency energy delivery in proximity to metallic medical device components.
abstract: BACKGROUND
  Radiofrequency (RF) ablation of cardiac arrhythmias is often performed in the presence of metallic materials in the heart.
  
  
  OBJECTIVE
  We hypothesize that metal objects in proximity to an RF ablation source can lead to ohmic heating of surrounding tissue. Furthermore, we hypothesize that insulation of the metal can mitigate this RF effect.
  
  
  METHODS
  A model consisting of viable bovine myocardium or thermochromic liquid crystal medium, a circulating saline bath at 37°C, and a load cell was used. A 4-mm RF ablation catheter was positioned with 10 g of force over bovine myocardium and placed in proximity to a copper wire, a defibrillator lead, and a circular mapping catheter. RF was applied at 30 W, and tissue temperatures were measured. Ablation near insulated and noninsulated esophageal temperature probes was also performed.
  
  
  RESULTS
  Ablation in proximity to metal resulted in higher temperatures. Average maximum distances for observed thermal changes to >45°C for the ± lead were 5.2 ± 0.3 mm and 5.7 ± 0.4 mm when metal was interposed between the catheter and the ground electrode. Presence of an esophageal temperature probe increased temperatures in tissues adjacent to the probe and caused lesions remote to the ablation site. Esophageal probe insulation prevented these tissue temperature increases and injury to nontargeted tissues.
  
  
  CONCLUSIONS
  Effects of RF ablation are potentiated near metallic components of medical devices, leading to significant tissue heating. Further research is needed to assess the safety impact of RF in the myocardium near metallic objects, particularly esophageal temperature probes.
authors.affiliation: Section of Cardiac Electrophysiology, Division of Cardiology, University of Colorado, Aurora, Colorado.
authors.forename: Duy T
authors.initials: DT
authors.lastname: Nguyen
authors.affiliation: Section of Cardiac Electrophysiology, Division of Cardiology, University of Colorado, Aurora, Colorado.
authors.forename: Waseem
authors.initials: W
authors.lastname: Barham
authors.affiliation: Section of Cardiac Electrophysiology, Division of Cardiology, University of Colorado, Aurora, Colorado.
authors.forename: Lijun
authors.initials: L
authors.lastname: Zheng
authors.affiliation: Section of Cardiac Electrophysiology, Division of Cardiology, University of Colorado, Aurora, Colorado.
authors.forename: Sarah
authors.initials: S
authors.lastname: Dinegar
authors.affiliation: Section of Cardiac Electrophysiology, Division of Cardiology, University of Colorado, Aurora, Colorado.
authors.forename: Wendy S
authors.initials: WS
authors.lastname: Tzou
authors.affiliation: Section of Cardiac Electrophysiology, Division of Cardiology, University of Colorado, Aurora, Colorado. Electronic address: william.sauer@ucdenver.edu.
authors.forename: William H
authors.initials: WH
authors.lastname: Sauer
mesh_terms: D000818:Animals; D001145:Arrhythmias, Cardiac / Q000473:pathology / Q000601:surgery*; D001831:Body Temperature; D017115:Catheter Ablation / Q000295:instrumentation*; D002417:Cattle; D004195:Disease Models, Animal; D004566:Electrodes; D006358:Hot Temperature; D008422:Materials Testing / Q000379:methods*; D009206:Myocardium / Q000473:pathology*; D013817:Thermography / Q000379:methods*
keywords: Esophageal temperature probe; Metal proximity; Ohmic heating; Radiofrequency ablation; Remote heating