Effects of Blood Flow on the Tip Contact Force of Cardiac Ablation Catheters

Robotic Catheter Ablation is a teleoperated robotic procedure. The robotic system for this procedure has a leader-follower configuration, thus lacking direct human touch on organs and instruments. However, the sense of touch is replaced by force sensor feedback that enables surgeons to monitor the contact force between the catheter and the patient's heart. Due to the high cost of sensorized cardiac catheters, sensor-free force estimation techniques have gained momentum in the state of the art. These techniques, for the most part, neglect the effects of blood flow in the left atrium, while recent clinical evidence suggests that blood flow disturbance can affect the stability and safety of catheter tip-tissue contact. This study was aimed at identifying the mechanisms by which blood flow may compromise tip-tissue contact force and quantifying such effects systematically. To this end, first utilizing a closed-loop flow channel, we examined the effects of blood (represented by water) flow on the magnitude of the tip contact force at physiological and pathological flow rates in 3D-printed pulmonary veins. Also, five configurations of an ablation catheter were considered to investigate the combined effects of catheter deflection and positioning of the catheter tip. Our results show that the tip contact force can greatly change because of the fluid flow, e.g., up to 37% when the catheter is close to the left inferior pulmonary vein. Also, even in the absence of blood flow, the maximum contact force was observed to reduce by increasing the catheter deflection. Diminishing tip contact force was exacerbated at higher flow rates. This study provides a quantitative mechanical explanation of why robotic ablation may result in suboptimal right inferior pulmonary vein isolation.