Bipolar radiofrequency ablation: The impact of tip load, application duration, power, and indifferent electrode size on the transmurality of a lesion

Background The main determinant of the radiofrequency (RF) ablation effect is transmurality of the lesion. Bipolar radiofrequency ablation (BA) creates transmurality in a higher proportion of cases than unipolar ablation (UA), but little is known about optimal RF settings. Material and methods This study aimed to compare UA and BA based on different application time, cathode tip load, anode size and power settings for achieving a transmural lesion in vitro. A Thermocool electrode was used for ablation (cathode) and a 4 mm or 8 mm tip catheter was used as the ground electrode (anode) for BA. The tested settings were tip load (10 g and 20 g), power (30 W or 40 W), and application duration (30, 60, or 90 s). After ablation, we measured scar size and transmurality of the lesion. Results BA created significantly larger and deeper scars compared with UA. Transmurality was achieved respectively in 42% and 2% of cases (p<0.001). Higher tip load resulted in larger scar size, and transmurality was achieved in 37% and 20% of cases (p=0.05). Scar size and transmurality increased with RF duration (5%, 39% and 42% of specimens, respectively (p<0.001). Bigger tip size of the ground electrode was related to higher transmurality (22% vs 61%, p<0.001). No relationship was found between power and transmurality. Optimal parameter settings were 20 g tip load, indifferent electrode with 8 mm tip, and 90 s RF duration (97.6% transmurality). Conclusions BA is more effective than UA in achieving transmural lesions. Optimal settings for BA consist of longer RF duration, higher tip load, and bigger tip size of the indifferent electrode.