Catheter Ablation -> Atrial Fibrillation & Atrial Flutter: -> Ablation Techniques D-PO01-NC - Non-CME Poster Session (ID 14) Poster

D-PO01-NC-02 - Intra-lesion Temperature Rise And Local Impedance Drop Predictive Of Lesion Growth On Rf Ablation Catheter With Mini Electrodes (ID 825)

  K.E. Garrott: Salary from Employment (Commercial Interest) - Boston Scientific.
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Background: Cardiac RF lesions form at tissue temperatures >50°C. Open-irrigated ablation and chamber flow limit catheter temperature sensing as a measure of lesion growth. A metric such as local impedance (LI, DIRECTSENSE™, Boston Scientific) that is sensitive to volumetric tissue heating could provide feedback on lesion formation.
Objective: To evaluate the relationship between LI and tissue heating during RF ablation in an in vitro model.
Methods: Intra-lesion temperature was measured using 3 51µm thermocouples placed 0, 2, and 4mm into explanted swine tissue. LI was measured with only ablation catheter electrodes, and starting impedance controlled at 120Ω. RF was applied until a 10, 20, 30, or 35Ω drop was achieved at powers of 20, 30, 40, and 50W.
Results: Lesions (n=59) were created. With a monoexponential fit, 2mm and 4mm temperature better predicted lesion depth (R=0.79 and R=0.82, respectively) than 0mm surface temperature (R=0.5). LI drop also strongly predicted lesion depth (R=0.79). LI drop and 2mm temperature had a strong linear correlation, as did rate of change (R=0.86, measured by time to 63% maximum rise or drop, Figure). Target LI drops of 10, 20, 30, and 35Ω resulted in lesion depths of 0.96±0.6, 1.9±0.4, 2.6±0.7, and 3.5±0.8mm and maximum 2mm temperatures of 64±6.8, 73±11, 89±9.4, and 96±4.2°C, respectively.
Conclusion: LI drop indicates volumetric tissue heating with high fidelity to intra-lesion temperature across a range of delivered power. This in vitro data demonstrate that LI is a valuable indicator of intra-lesion temperature, with LI drops larger than 10Ω creating lesions greater than 1mm in depth with a maximum temperature greater than 64°C.