Numerical simulations of temperature inside the heart tissues to evaluate the performances of cryoablative probe

Abstract

In the present paper the behaviour of human cardiac tissue during cryo-ablation is simulated with a finite difference algorithm which solves the Pennes' equation including the phase change during freezing of the cardiac tissues. The evolution of temperatures at different points is calculated and the movement of the ice front is obtained from simulation results. All phenomena related to heat transfer in living tissue are considered: heat conduction, heat release and absorption due to heat capacity, metabolism and blood perfusion. Although the geometry and the assumed boundary conditions are quite simple, the structure of the developed model can be easily adapted to more complex geometries. Model results show for instance that with a power of 10 W tissues distant 0.5 mm from the probe are ablated, while the other tissues more than 0.5 mm remain at −20 °C, so undamaged The results also show that the outcome of cryo-ablation treatment depends on many parameters: operational parameters such as the power heat absorbed by the probe (i.e. the mass flow rate of the cryo-fluid) and the duration of therapy application; biothermal parameters such as metabolic heat flux and blood perfusion; thermophysical properties of the tissue. Among these the effects of both blood perfusion and metabolic rate result less influencing. The numerical model presented could be useful to estimate the best conditions for the application of the probe during treatment and the possible change of the cure parameters to adapt the therapy to different patients.