Flow field study of radiofrequency ablation of renal sympathetic nerve: Numerical simulation and PIV experiments.

Renal sympathetic denervation (RSD) is a new method for the treatment of resistant hypertension (RH). However, few studies have focused on the effects of RSD on blood flow and the interaction between temperature field and flow field. In this paper, firstly, we designed a numerical simulation of electromagnetic field, flow field and temperature field coupling by finite element method. Secondly, numerical simulation results were verified by particle image velocimetry (PIV) and vitro experiment. From the simulation results, when the flow velocity increases to 0.05 m/s, the turbulence near the electrode disappeared and flow state became uniform laminar flow. With the increases of flow velocity (0 m/s to 0.1 m/s), temperature rise of the renal artery, the electrode tip and blood decreased from 13°C, 24°C and 5.4°C to 9.3°C, 9.7°C and 0.2°C, respectively. From PIV experiment and vitro experiment results, when the flow rate increases to 0.5 L/min, it appeared similar phenomenon with the velocity of 0.05 m/s in simulation. With the increases of flow rate (0 L/min to 0.8 L/min), temperature rise of three points decreased from 11.2°C, 20.5°C and 3.6°C to 7.8°C, 8.5°C, and 0.4°C, respectively. When the blood flow rate exceeds 0.5 L/min, there is no large velocity gradient and reflux area in the flow field, so there will be no hemolysis and thrombosis. Therefore, the temperature field has less influence on the flow field. With the increase of flow rate, the temperature at all three points decreases. Therefore, the flow field has an effect on the temperature field. But the central temperature of renal artery can still reach the treatment target in which temperature rises to be more than 6°C. Therefore, this study preliminarily verified the safety and effectiveness of RSD.