Numerical model for radio-frequency ablation of the endocardium and its experimental validation

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Abstract
A theoretical model for the study of the radiofrequency (RF) ablation technique is presented. The model relies on a finite-element time-domain calculation of the temperature distribution in a block of tissue, resulting from the flow of RF (<1 MHz) electrical current. A thermal damage function is used to calculate the extent of the lesion on the basis of the temperature elevation and the duration of exposure. This work extends the model proposed by D.E. Haines and D.D. Watson (PACE, vol.12, p.962-76, 1989) by including a more realistic and variable geometry, the cooling effect of the blood flow and a transient analysis. Furthermore, the nonlinearity caused by the temperature dependence of the tissue properties is also considered. The complexity of the model being appreciable, an experiment demonstrating its validity is also described. While remaining workable, the experiment is sophisticated enough to lead to convincing conclusions. It consists in measuring the temperature distribution and the time-dependent electrode resistance during "ablation" of a tissue-equivalent material. Various electrode configurations and electrical excitations are investigated. In all cases, the experimental results agree reasonably well with the numerical calculations. This confirms that the model is accurate for the investigation of RF ablation.