New method for predicting efficiency of heating by measuring bioimpedance during radiofrequency catheter ablation in humans

Introduction: Efficiency of heating (defined as the average temperature div ided by the average power) during radiofrequency (RF) catheter ablation (RF CA) 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 heatin g 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 u sing an extremely low current (10 muA at 45 kHz), Tip electrode temperature was measured with a closed-loop RF generator. Efficiency of heating and th e difference (Delta bioimpedance) between preablation bioimpedance (measure d from the target ablation site) and baseline bioimpedance (measured in the right atrium without tissue contact) were calculated. There was significan t positive correlation between preablation bioimpedance and efficiency of h eating (regression coefficient = 0.053; P = 0.003) and between Delta bioimp edance 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 Delta bioimpedance > 21.5 Ohm, applications targeted at th e left free-wall, left posteroseptal, or right septal accessory pathways ha d a greater likelihood of achieving effective tissue heating (defined as ma ximal temperature achieved > 55 degreesC), Conclusion: Both preablation bioimpedance and Delta bioimpedance have posit ive 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.