Randomized comparison of two techniques for titrating power during radiofrequency ablation of accessory pathways

Impedance Versus Temperature Monitoring. Introduction: The purpose of this study was to prospectively compare the value of impedance and temperature monitoring during accessory pathway ablation. Temperature and impedance monitoring can be used during radiofrequency ablation of accessory pathways to titrate power to achieve adequate but not excessive tissue heating. Methods and Results: One hundred thirty-two patients with a single accessory pathway were randomly assigned to undergo ablation using either impedance monitoring or temperature monitoring. During impedance monitoring, the endpoint for titration of power was a 5- to 10-Ω decrease in the measured impedance while for temperature monitoring the endpoint was to achieve a temperature of 58° to 62°C. Two protocols were used. In protocol 1 (90 patients), impedance monitoring was performed with a nonthermistor catheter and temperature monitoring was performed with a thermistor catheter. In protocol 2 (42 patients), a thermistor catheter was used in all patients. In protocol 1, the success rate (93% vs 93%; P = 1.0), ablation procedure duration (57 ± 56 vs 41 ± 41 min), fluoroscopy time (48 ± 29 vs 41 ± 23 min; P = 0.3), number of applications (6.2 ± 4.7 vs 5.7 ± 4.6; P = 0.8), and the number of applications associated with coagulum formation (0.1 ± 0.3 vs 0.3 ± 0.6; P = 0.1) were similar in the two groups. In protocol 2, as in protocol 1, there were no differences in the success rate (91% vs 95%; P = 1.0), ablation procedure duration (49 ± 37 vs 62 ± 55 min; P = 0.4), fluoroscopy time (46 ± 24 vs 49 ± 36 min; P = 0.8), number of applications (6.8 ± 7.0 vs 7.8 ± 12.1; P = 0.7), or number of applications associated with coagulum formation (0.3 ± 0.6 vs 0.2 ± 0.7; P = 0.6) between the impedance and temperature monitoring groups. Conclusion: Temperature and impedance monitoring are equally effective in optimizing the results of accessory pathway ablation.