Purpose: Contact force (CF) sensing during radiofrequency (RF) ablation allows controlling lesion size. The aim of this study was to analyze the impact of catheter tip location and orientation on the association of CF and impedance decrease.
Methods: We retrospectively analyzed RF applications from 32 patients undergoing catheter ablation for paroxysmal atrial fibrillation using a force-sensing catheter and 3D mapping system. CF, catheter location and orientation relative to the tissue during ablation as well as the absolute impedance decrease during the first 20 s of ablation as a surrogate for lesion effectiveness were analyzed for 791 RF applications.
Results: While a higher CF was achieved around the right pulmonary veins (12.5 vs. 11.4 g, p = 0.045), a lower median absolute impedance decrease within the first 20 s was seen around the right veins compared to the left veins (9.3 vs. 10.2 Ω, p = 0.02). With different catheter orientations relative to the tissue, higher CF and impedance decrease was seen when the catheter was orientated parallel or oblique to the tissue (30°-145°) as compared perpendicularly (0-30°) with a median CF of 13.2 vs. 8.0 g (p < 0.001) and a median impedance decrease during the first 20 s of 11 vs. 7 Ω (p < 0.001). Importantly, achieved CF, baseline impedance, catheter orientation and location all independently predicted the initial absolute and relative impedance decrease in a multivariable linear regression model (p < 0.05).
Conclusions: The effectiveness of RF ablation lesions, as assessed by the initial impedance decrease, is not only dependent on the achieved catheter CF but also on catheter orientation and location.