Clinical evaluation of a new technique to monitor return electrode skin temperature during radiofrequency ablation

Abstract

Purpose: 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.

Methods and 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.

Conclusion: 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.