Simulation Analysis And Control System Design Of Contact Force Factors In Cardiac Radiofrequency Ablation

Cardiac radiofrequency(RF)ablation is a first-line or quasi-first-line treatment option for conditions such as arrhythmias,atrial fibrillation and ventricular tachycardia.Factors affecting the effectiveness of RF ablation treatment include RF power,ablation time and tissue temperature.Currently,with the widespread use of pressure-monitored radiofrequency ablation catheters in clinical practice,the influence of the contact force between the ablation electrode and myocardial tissue on the ablation effect has become one of the current research hotspots in the field of radiofrequency ablation.To analyze the role of contact force,a finite element model of cardiac RF ablation with coupled temperature-electromagnetic-mechanical fields is constructed in this paper;and a RF ablation catheter contact force control system is designed to control the contact force of the ablation electrodes.Specifically,the main elements are as follows:First,based on the heat transfer equation,thermoelastic mechanical modeling equation of myocardial tissue,and thermal lesion assessment equation during RF ablation,a coupled temperatureelectromagnetic-mechanical multiphysics field model for cardiac RF ablation was established using Comsol Multiphysics.The effect of different ablation parameters on ablation thermal lesions was investigated by the results of finite element model calculations of cardiac radiofrequency ablation.With the increase of contact force,the size of thermal lesion zone,thermal lesion permeability,and thermal lesion zone width/depth ratio all increase,however,the thermal lesion generation time changes less;force-time integral(FTI)as a predictor of thermal lesion has good accuracy in the preablation period,but decreases as the ablation time increases;In addition,the thermal convection coefficient,tissue parameters and shrinkage coefficient all affect the thermal lesion size as well as the maximum temperature inside the tissue.Secondly,to achieve accurate control of ablation electrode contact force,the RF ablation catheter contact force control system based on the lower computer and upper computer was designed.Among them,the lower computer hardware part uses Arduino Mega2560 as the control core,resistive pressure sensor as the contact force measurement element,stepper motor and drive unit as the control module,and bluetooth as the wireless data transmission module;the upper computer hardware part uses PC.In the software part,the lower computer program receives,processes,converts and sends the voltage value from the pressure sensor and calculates the control amount of the stepper motor using the hybrid PID control system;the upper computer Lab VIEW program receives the value from the pressure sensor and calculates the real-time FTI value.Finally,an experimental platform for the catheter contact force control system was built to carry out experiments to evaluate the dynamic response and safety performance,and to verify whether the required target FTI can be achieved in the specified time under the system steady state.The experimental results show that the system can enter and recover to the steady state relatively quickly under both step input and disturbed conditions;the steady state system controls the contact force within a certain range and reaches the required FTI within a specified time.