Key result
Transfer function models estimate real-time RF ablation tissue temperature within ~4ºC of finite element simulations.
Why the study?
Can mathematical models based on transfer functions accurately estimate tissue temperature during radiofrequency cardiac ablation compared to finite element models?
Can mathematical models based on transfer functions accurately estimate tissue temperature during radiofrequency cardiac ablation compared to finite element models?
Effect estimate: <4ºC difference
Mathematical models based on transfer functions can estimate tissue temperature during radiofrequency cardiac ablation in real time with an error of less than 4ºC compared to finite element models.
Real-time temperature estimation remains investigational during ablation; leaves open clinical translation pending human validation.
Radiofrequency cardiac ablation (RFCA) has been used to treat certain types of cardiac arrhythmias by producing a thermal lesion. Even though a tissue temperature higher than 50ºC is required to destroy the target, thermal mapping is not currently used during RFCA. Our aim was thus to develop mathematical models capable of estimating tissue temperature from tissue characteristics acquired or estimated at the beginning of the procedure (electrical conductivity, thermal conductivity, specific heat and density) and the applied voltage at any time. Biological tissue was considered as a system with an input (applied voltage) and output (tissue temperature), and so the mathematical models were based on transfer functions relating these variables. We used theoretical models based on finite element method to verify the mathematical models. Firstly, we solved finite element models to identify the transfer functions between the temperature at a depth of 4 mm and a constant applied voltage using a 7Fr and 4 mm electrode. The results showed that the relationships can be expressed as first-order transfer functions. Changes in electrical conductivity only affected the static gain of the system, while specific heat variations produced a change in the dynamic system response. In contrast, variations in thermal conductivity modified both the static gain and the dynamic system response. Finally, to assess the performance of the transfer functions obtained, we conducted a new set of computer simulations using a controlled temperature protocol and considering the temperature dependence of the thermal and electrical conductivities, i.e. conditions closer to those found in clinical use. The results showed that the difference between the values estimated from transfer functions and the temperatures obtained from finite element models was less than 4ºC, which suggests that the proposed method could be used to estimate tissue temperature in real time.
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Alba-Martínez et al. (2012) studied Cardiac arrhythmias (Radiofrequency cardiac ablation). Mathematical models based on transfer functions vs. Finite element method (FEM) models was evaluated on Difference between estimated temperature and FEM-derived temperature (<4ºC difference). Mathematical models based on transfer functions estimated tissue temperature during radiofrequency cardiac ablation in real time with an error of less than 4ºC compared to finite element method simulations.
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