Electrode Thermal Profile During Ventricular RF Ablation

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BACKGROUND: Electrode-tissue contact and orientation influence radiofrequency (RF) ablation heating, lesion size, and steam pops, and is not easily assessed. A catheter with 6 distal electrode temperature sensors provides thermal profiles that may help clarify electrode-tissue interactions. OBJECTIVES: The aim of this study was to evaluate the relationships between thermal profiles, catheter orientation, impedance fall, steam pops, and discordant temperature-impedance changes during ventricular RF ablation. METHODS: We analyzed 2,085 RF applications in 100 patients, titrating power to a maximum temperature <50 °C and impedance fall >10 Ω. Stable thermal profiles were classified as embedded, central, or peripheral. Catheter orientation from the force vector was classified as perpendicular, oblique, or parallel. RESULTS: The thermal profile aligned with the force vector at 60.9% of stable sites, with 72.1% of peripheral profiles being oblique/parallel and 80.4% of central profiles being perpendicular. Impedance fall was discordant with temperature at 890 (42.7%) sites. Catheter orientation and thermal profiles differed for low temperature-high impedance fall, compared with high temperature-low impedance fall discordant sites (P < 0.001). An embedded thermal profile (all sensors ≥45 °C) most often occurred with perpendicular or oblique orientations, had the greatest impedance falls, and had the highest incidence of steam pops (8.6% vs 1.3%; P < 0.001). No steam pops occurred with impedance falls <14 Ω or maximum temperature <45.8 °C, or when impedance fall and temperature were discordant. CONCLUSIONS: Electrode thermal profiles provide information complementary to force vector and impedance, reflecting electrode-tissue interactions that are also related to discrepancies in impedance fall and temperature during RF ablation. They can potentially help optimize RF ablation lesion size while avoiding steam pops.

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