Should fluid dynamics be included in computer models of RF cardiac ablation by irrigated-tip electrodes?

Figures

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  Fig. 1. Geometry of the three-dimensional computational models built (not to scale). Cardiac tissue thickness (H) was 20 mm and the dimensions of cardiac chamber X and Y (Z = Y) were obtained from a convergence test. RF current flows between an active electrode and the dispersive electrode (bottom). The active electrode (7Fr, 4 mm) is a multi-hole open-irrigated electrode, which is assumed to be inserted into cardiac tissue to a depth DE. In the reduced model the saline irrigation through the small holes in the electrode tip is simply modeled by fixing a temperature condition of 40 °C on its surface, while in the full model it is modeled by an inlet velocity boundary condition Usaline at the electrode-blood interface. Thermal lesion is assessed by the 50 °C isotherm and its geometry is characterized by: maximum depth (D), maximum width (MW), depth at the maximum width (DW) and surface width (SW)

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  Fig. 2. Boundary conditions of the models: a electrical boundary conditions, b thermal boundary conditions for the reduced model, and c thermal and velocity boundary conditions for the full model

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  Fig. 3. Temperature distributions at 10 s (a) and 60 s (b) obtained with the full model. Solid lines are those of the lesion boundaries computed by the full model while dashed lines are those computed by the reduced model

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  Fig. 4. Comparison of the progress of lesion depth (a), surface width (b) and maximum width (c) between the reduced (red lines) and the full (blue lines) models, for high and low blood flow rates and three electrode insertion depths (DE) (0.5, 1.0 and 1.5 mm)

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  Fig. 5. Comparison of the progress of maximum temperatures reached in the tissue (a) and blood (b) between the reduced (red lines) and full (blue lines) models, for high and low blood flow rates and three electrode insertion depths (DE) (0.5, 1.0 and 1.5 mm)

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  Fig. 6. Temperature distributions at 60 s (a) for the full model (black and white solid lines are those of the lesion boundaries computed by the full and reduced model, in this case multiplying by three the thermal convective coefficients. The dashed line is that computed by the reduced model using the previous thermal convective coefficients) and the comparison of progress of maximum blood temperatures (b) between the reduced (red lines) and full (blue line) models for low blood flow rate using an electrode insertion depth (DE) of 1.0 mm. The rationale for increasing the value of thermal convective coefficients at both interfaces was to try to match the lesion surface width of the reduced model with that of the full model