title: Clinical evaluation of a new technique to monitor return electrode skin temperature during radiofrequency ablation.
abstract: OBJECTIVE
  Return electrode burns occur occasionally in cardiac radiofrequency ablation and more frequently in tumor radiofrequency ablation. A return electrode incorporating a thermochromic liquid crystal (TLC) layer, which changes color with temperature, has been shown in sheep studies to accurately indicate underlying skin temperature. We aimed to validate the accuracy of TLC-coated return electrodes in indicating skin temperature in the clinical setting of cardiac radiofrequency ablation.
  
  
  RESULTS
  The top layer of a standard return electrode was replaced with TLC. Fluoro-optic thermometer (FOT) probes were laid on the skin side of the return electrode, which was then placed on the left lateral mid-thigh of 18 patients (mean age = 61 ± 12 years, 12 men) undergoing cardiac radiofrequency ablation. Return electrode photographs were taken when FOT temperature exceeded 35 °C. TLC color changes, observed in 11 patients, were converted to temperature and compared with FOT temperature. TLC temperature correlated well with FOT temperature (Pearson's coefficient = 0.97 ± 0.03). Bland-Altman analysis showed good agreement (mean temperature difference = -0.04 ± 0.08 °C, upper limit of agreement = 0.11 ± 0.005 °C, lower limit of agreement = -0.19 ± 0.005 °C). The maximum FOT temperature recorded was 39.6 °C. There was no thermal injury at the return electrode site on any patients, when assessed immediately after and the day following the procedure.
  
  
  CONCLUSIONS
  TLC-coated return electrodes accurately indicate underlying skin temperature in cardiac radiofrequency ablation and may help prevent burns. This technology might be essential in high energy radiofrequency ablation.
authors.affiliation: Department of Cardiology, Westmead Hospital, Sydney, Australia.
authors.forename: Siddharth J
authors.initials: SJ
authors.lastname: Trivedi
authors.forename: Toon Wei
authors.initials: TW
authors.lastname: Lim
authors.forename: Michael A
authors.initials: MA
authors.lastname: Barry
authors.forename: Karen
authors.initials: K
authors.lastname: Byth
authors.forename: David L
authors.initials: DL
authors.lastname: Ross
authors.forename: Aravinda
authors.initials: A
authors.lastname: Thiagalingam
authors.forename: Pramesh
authors.initials: P
authors.lastname: Kovoor
mesh_terms: D000368:Aged; D002058:Burns, Electric / Q000209:etiology / Q000517:prevention & control*; D017115:Catheter Ablation / Q000009:adverse effects / Q000295:instrumentation*; D004566:Electrodes; D004867:Equipment Design; D019544:Equipment Failure Analysis; D004869:Equipment Safety / Q000379:methods; D005246:Feedback; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative / Q000295:instrumentation*; D012867:Skin / Q000293:injuries; D012881:Skin Temperature / Q000502:physiology*; D013817:Thermography / Q000295:instrumentation*