777-2 Predictors of Abrupt Impedance Rise During Chilled-Tip Radiofrequency Catheter Ablation

Abstract

Electrode tip temperature monitoring during standard radiofrequency (RF) current catheter ablation can be used to prevent abrupt impedance rise (IR) associated with tip temperatures > 100°C. Electrode tip chilling during RF ablation by intraelectrode saline infusion can also reduce the likelihood of abrupt IR and allow larger lesion formation. However, both the utility of tip temperature monitoring during tip chilling and the registered tip temperature associated with IR are unknown. Twelve sheep (mean wt. 65 kg) received chilled RF ablation at up to 8 separate LV sites. High power RF current of 40, 50, 60 or 70W was delivered via modified 7Fr deflectable catheter with a 4 mm tip through which saline (26°C) was continuously infused at 0.6 mllsec. RF current duration was 60 seconds or until IR occurred. Tip temperature was continuously monitored by electrode tip thermocouple. A total of 95 applications of RF current were analyzed, of which 40 resulted in an abrupt IR. The frequency of IR increased with higher power applications (40W-8.3%, 50W-23%, 60W-63%, 70W-71%). Abrupt IR was observed at a mean temperature of 75.0 ± 11.8°C (range 44.4 to 94.7°C). This temperature was significantly higher than for RF applications not associated with IR (49.8 ± 8.3°C; P < 0.001). An abrupt IR was observed in all cases with tip temperature ≥67°C (N = 32). Audible “popping” emanating from the catheter tip occurred during 20 RF current applications, and most (90%) were associated with abrupt IR. Electrode tip temperature monitoring is useful during chilledtip RF ablation, but the thermocouple registers a lower temperature at the time of impedance rise compared to traditional RF ablation.