Tripolar versus bipolar ablation: insights into lesion growth and geometry using a novel ablation approach for therapy-refractory ventricular arrhythmias.

Efficacy of bipolar radiofrequency ablation (BA) is often limited by high impedance between the two ablation catheters in cases of therapy-refractory ventricular tachycardias. Tripolar ablation (TA) is a novel approach, adding a dispersive return electrode to BA. The study aimed to investigate differences in lesion growth and geometry in BA and TA using variable power (20-50W) during power-controlled, irrigated radiofrequency ablation on cross-sections of porcine heart preparations in an ex-vivo model. Using high-resolution imaging at one-second intervals, 1694 measurements in 40 lesions were analyzed regarding lesion geometries and ablation parameters. Baseline impedance was lower in TA (213.1 ± 20.6 Ω vs. 242.7 ± 23.6 Ω, p < 0.001) and distinct differences in lesion geometry were present. Specifically, TA produced deeper and wider lesions at the active catheter compared to the return catheter, resulting in trapezoidal lesions in contrast to rectangular lesions in BA. All lesions reached transmurality; however, lesion width continued to increase in BA and TA after transmurality had been achieved. The majority of steam pops (16/18) occurred above 40W without differences in BA and TA. In cases of high baseline impedance, TA using an additional dispersive return electrode seems effective. In this experimental setup, TA creates trapezoidal lesions in contrast to rectangular lesions in BA without an associated increase in the risk of steam pops.