New Method for Predicting Efficiency of Heating by Measuring Bioimpedance During Radiofrequency Catheter Ablation in Humans

Abstract

Bioimpedance During Radiofrequency Catheter Ablation. Introduction: Efficiency of heating (defined as the average temperature divided by the average power) during radiofrequency (RF) catheter ablation (RFCA) can be predicted by the electrode‐tissue contact pressure before RFCA. To predict the efficiency of heating during RFCA, we prospectively measured bioimpedance and correlated the bioimpedance with the efficiency of heating in patients undergoing RFCA for supraventricular tachycardias. Method and Results: Of 239 RF applications in 55 patients, bioimpedance was measured from the distal pair of the electrodes of the ablation catheter using an extremely low current (10 μ A at 45 kHz). Tip electrode temperature was measured with a closed‐loop RF generator. Efficiency of heating and the difference (Δbioimpedance) between preablation bioimpedance (measured from the target ablation site) and baseline bioimpedance (measured in the right atrium without tissue contact) were calculated. There was significant positive correlation between preablation bioimpedance and efficiency of heating (regression coefficient = 0.053; P = 0.003) and between Δbioimpedance and efficiency of heating (regression coefficient = 0.067; P = 0.003). The highest degree of correlation was found during RFCA of the accessory pathways in the left free wall (regression coefficient = 0.14; P < 0.01). With preablation Δbioimpedance > 21.5 Ω, applications targeted at the left free‐wall, left posteroseptal, or right septal accessory pathways had a greater likelihood of achieving effective tissue heating (defined as maximal temperature achieved > 55°C). Conclusion: Both preablation bioimpedance and Δ bioimpedance have positive correlation with efficiency of heating during RFCA of supraventricular tachycardia. Measuring preablation bioimpedance appears to be a useful tool for predicting the efficiency of heating during RFCA.

Radiofrequency and Irrigated Ablation: Principles and Potential for Renal Artery Denervation (RDN) in the Treatment of Resistant Arterial Hypertension

“…As tissue is heated, there is a temperature-dependent drop in electrical impedance. A signifi cant positive correlation between preablation impedance and heating effi cacy was demonstrated, and a similar association has been observed between maximum drop in impedance during energy delivery and heating effi cacy [ 9 ]. Temperature monitoring also provides useful information about the quality of electrode/tissue contact.…”

Impedance and Temperature Monitoring Improve the Safety of Closed‐Loop Irrigated‐Tip Radiofrequency Ablation

“…[6][7][8] The impedance drop during radiofrequency (RF) ablation has been postulated to be secondary to increased myocardial tis- sue temperature. 7,9,10 However, the biophysical mechanisms underlying impedance change during RF ablation are still unclear. It is also unclear whether the impedance fall during ablation is due to irreversible changes in the myocardium or to reversible factors (e.g., temperature).…”

“…Titration of RF power using the drop‐in impedance during ablation has been proposed as an alternative strategy to temperature‐controlled or fixed‐power ablation protocols 6–8 . The impedance drop during radiofrequency (RF) ablation has been postulated to be secondary to increased myocardial tissue temperature 7,9,10 . However, the biophysical mechanisms underlying impedance change during RF ablation are still unclear.…”

Observations on Attenuation of Local Electrogram Amplitude and Circuit Impedance During Atrial Radiofrequency Ablation: An In vivo Investigation Using a Novel Direct Endocardial Visualization Catheter

“…The relationship between lesion growth and electrogram diminution has not been studied in detail until the recent introduction of microelectrode (ME) embedded catheters . Impedance decrement during ablations is another metric used to guide ablation time, and has been studied extensively for its usefulness as a surrogate marker for effective lesion formation and also to predict complications; however, the association with lesion growth remains unclear …”