Approximate Thermal Modeling of Radiofrequency Cardiac Ablation Approximate Thermal Modeling of Radiofrequency Cardiac Ablation
The approximate thermal model uses a convective boundary condition to account for convective cooling of the myocardial surface. This model also uses a point source rather than the complicated heat generation function that accounts for the spatial variation of the voltage in the cardiac tissue. A C program was written to evaluate the engineering model. The effect of the convection coefficient (h), the depth at which the point source is located (zo), and the power dissipation rate (P) on the 50 ˚C isotherm in the cardiac tissue is shown. The accuracy of the approximate model depends greatly on the values of these three parameters.
Rigorous three-dimensional numerical modeling was done in order to validate the engineering model. The numerical model was done using a commercial computational fluid dynamics (CFD) package. This software solved the steady, incompressible Reynolds-Averaged Navier-Stokes (RANS) equations—along with the Reynolds-Averaged energy transport equation—using an unstructured, segregated, pressure-based finite-volume procedure. This model is different from other numerical RF ablation models in that it took into account the turbulent flow of the blood. It also accounted for the effect of the flow past the electrode and the spatially varying heat generation function. The heat generation function was found from the solution of the Laplace equation to find the voltage distribution in the tissue.
The three unknown parameters governing the approximate thermal model were changed manually and good fits of the approximate model with the numerical model resulted, proving that the engineering model can accurately predict the size of the 50 ˚C isotherm in the cardiac tissue.
School:Brigham Young University
School Location:USA - Utah
Source Type:Master's Thesis
Keywords:heat transfer rfca radiofrequency ablation
Date of Publication:08/09/2005