Impact of tip design and thermocouple location on the efficacy and safety of radiofrequency application.

Abstract

The FlexAbility™ SE catheter has a laser-cut 8Fr 4-mm flexible tip irrigated through laser-cut kerfs with a thermocouple 0.3mm from the distal end. The TactiCath™ SE catheter has an 8Fr 3.5-mm tip and 6-irrigation port with a thermocouple 2.67mm proximal to the tip. We investigated the impact of these differences on the efficacy and safety of radiofrequency (RF) applications. RF applications at a range of powers (20W, 30W, and 40W), contact forces (5g, 15g, and 25g), and durations (10-60s) using perpendicular/parallel catheter orientation were performed in excised porcine hearts. Lesion characteristics and incidence of steam pops were compared. A total of 540 lesions were examined. The FlexAbility™ SE catheter produced smaller lesion depths (4.0mm vs. 4.4mm, p = 0.014 at 20W; 4.6mm vs. 5.6mm, p = 0.015 at 30W), surface areas (22.7mm2 vs. 29.2mm2 at 20W, p = 0.005; 23.2mm2 vs. 28.7mm2, p = 0.009 at 30W), and volumes (126.1mm3 vs. 175.1mm3, p = 0.018 at 20W; 183.2mm3 vs. 304.3mm3, p = 0.002 at 30W) with perpendicular catheter placement. However, no differences were observed with parallel catheter placement. Steam-pops were significantly less frequently observed with the FlexAbility™ SE catheter (4% vs. 22%, p < 0.001) irrespective of catheter direction to the tissue. Multivariate analysis showed that use of the TactiCath™ SE catheter, power ≥ 40W, contact force ≥ 25g, RF duration > 30s, parallel angle, and impedance drop ≥ 20Ω were significantly associated with occurrence of steam-pops. The FlexAbility™ SE catheter reduced the risk of steam-pops but produced smaller lesions with perpendicular catheter placement compared to the TactiCath™ SE catheter.