Abstract 12317: Initial Impedance Decrease as an Indicator of Good Catheter Contact: Insights From a Comparison of Ablation With Force Sensing and Standard RF Catheters
Background: The tissue heating during radiofrequency (RF) application results in a resistance decrease measured at the catheter tip, which correlates with contact force. The aim of our study was to compare initial impedance decrease during PVI procedures using either a force sensing or a standard RF catheter.
Methods: We analyzed 573 RF applications of at least 20 seconds duration in 10 patients undergoing PVI who were randomized to treatment with an irrigated force-sensing RF catheter (Tacticath, Endosense) or a standard irrigated RF catheter (Thermocool, Biosense-Webster). A steerable sheath was used in all patients and a contact force of at least 15g was achieved in the force-sensing catheter group.
Results: Patients in the force-sensing and the standard catheter group were well matched in terms of age, gender, EF and LA size. The initial impedance was similar for RF applications in both groups (140 vs. 142 ohms). The initial decrease in impedance was significantly greater in the force-sensing catheter group compared to the standard catheter group. Median values of decreases (IQR) were 9 (6-12) vs. 3 (2-6) ohms at 5s, 11 (7-14) vs. 5 (3-8) ohms at 10s and 12 (8-17) vs. 6 (2-11) ohms at 20s (p<0.001 for all comparisons, Figure). At 10 seconds, 90% of lesions using a force-sensing catheter and only 50% of lesions using a standard catheter had a minimum impedance decrease of 5 ohms.
Conclusions: The impedance decrease observed at the beginning of an RF application is significantly greater when good catheter contact is ascertained by a force-sensing catheter compared to a standard catheter. Monitoring of the impedance decrease can therefore be used to indirectly assess catheter tip contact during RF application with a standard catheter. A decrease of at least 5 Ohms in the first 10 seconds may be a reasonable surrogate for good contact.
- © 2012 by American Heart Association, Inc.