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endocardium failed. Mapping of the great cardiac vein performed with an irrigated 3.5-mm ablation catheter (AC) showed the earliest activation in the epicardial area of LVS. A second 4-mm AC, which served as a return catheter (RC), was introduced into LV outflow tract to the area of earliest endocardial PVC activation, and was connected to the modified purpose-made switchbox in order to connect the tip electrode (instead of dispersive patch) to B ipolar radiofrequency catheter ablation (RFCA) is an emerging option for treatment of arrhythmias resistant to standard unipolar attempts. A 43-yearold man was referred for bipolar ablation after 2 previously unsuccessful RFCA for symptomatic premature ventricular complexes (PVC) originating from the left ventricular summit (LVS; Figure A). Previous RFCA from the distal coronary venous system and from the anatomically adjacent IMAGES IN CARDIOVASCULAR MEDICINEAdvance Publication by-J-STAGE

Introduction Bipolar radiofrequency catheter ablation (Bi‐RFCA) emerged as an option for treatment of arrhythmias resistant to the conventional approach. Data on safety issues of Bi‐RFCA, including temperature values of intracardiac return electrode (IRE) are lacking. Objective To determine the safety profile of Bi‐RFCA regarding temperature measurements obtained from nonirrigated IRE of different sizes. Methods The study group consisted of consecutive patients after failed conventional RFCA who underwent Bi‐RFCA. Results Out of 1510 RFCA performed in our center, 19 patients underwent Bi‐RFCA due to refractory to previous RFCA ventricular arrhythmias (15 patients) or typical atrial flutter (four patients). Nonirrigated small (4 mm) and large (8 mm) tip catheters were used as IRE in 14 (including three cross‐overs to 8 mm IRE) and five patients, respectively. A total number of 164 bipolar applications were performed (128 for 4 mm and 36 for 8 mm IRE). Maximal temperatures of 4 mm IRE were significantly higher than those of 8 mm IRE (63°C ± 16°C vs 43°C ± 4°C; P = .027). A significant rise of temperature and steam‐pops, preventing further Bi‐RFCA, occurred in seven patients treated with 4 mm IRE. Bi‐RFCA using 4 mm IRE operated at significantly higher impedance values (211 ± 83 vs 143 ± 38; P = .04) and lower power values (mean 20 W ± 6 W vs 32 W ± 7 W, P = .0005; max 29 W ± 9 W vs 39 W ± 10 W, P = .027). Conclusion The use of 8 mm IRE for Bi‐RFCA is associated with lower temperatures of the catheter used as ground and lower incidence of steam‐pops which may suggest a better safety profile than 4 mm IRE. Determination of safety/efficacy balance requires further studies.

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