Bipolar versus unipolar radiofrequency ablation in ventricular arrhythmias: a comparative analysis of biophysical characteristics

Background Bipolar catheter ablation (Bi-RFA) has emerged as a treatment strategy for ventricular arrhythmias (VA) arising from deep intramural substrate. To date, no in vivo study has compared the periprocedural biophysical characteristics of bipolar and unipolar radiofrequency ablation lesions. Purpose The study aimed to compare the biophysical characteristics of ventricular uni- and bipolar ablation lesions in clinically comparable patient cohorts. Methods In this single-centre retrospective study, all consecutive patients (Group 1, n=36) undergoing Bi-RFA for VAs between January 2022 and February 2026 were included. These patients were compared with a clinically comparable unipolar ablation cohort (Group 2, n=36) selected from the prospective registry comprising 428 unipolar ablation procedures for VAs. Periprocedural data for all ablation points from each procedure were exported from the mapping system and analysed. In bipolar procedures only bipolar ablation points were assessed, even if additional unipolar ablation was performed. Results A total of 72 patients (36 per group) were included. Median age was 65 years, 81% were male, 51% had ischemic cardiomyopathy, and median left ventricular (LV) ejection fraction was 40% (IQR 25-50). The most patients (83%) underwent ablation for ventricular tachycardia whereas the remaining patients for primary ventricular contractions (Fig.1A). Baseline characteristics were comparable between groups, except for a higher proportion of previous VT ablation in the bipolar cohort (66.7% vs 22.2%, p<0.001). The most common targets of ablation were the interventricular septum (36% vs 42%, p=0.8), LV summit (33% vs 11%, p=0.045), LV free wall (25% vs 44%, p=0.14) (Figure 1B). The total number of ablation points (27 vs 32 points, p=0.104) and total RF application duration (647 vs 794 seconds, p=0.45) did not differ significantly between groups. However, bipolar procedures were associated with longer procedure time (175 vs 135.5 min, p=0.017), longer fluoroscopy duration (15.2vs 9.0 min, p<0.001), and higher radiation dose (1347 vs 564 cGy·cm², p<0.001). In the Bi-RFA group a median of 9 (IQR7-14) bipolar applications with 300 seconds (IQR184-435) RF duration were delivered. Bipolar ablation was associated with significantly higher baseline impedance (138 vs 104 Ω, p<0.001). Despite lower average delivered power (30 vs 45 W, p<0.001), bipolar ablation resulted in a greater absolute impedance drop (20.9 vs 8.0 Ω, p<0.001) and greater relative impedance reduction (13.4% vs 8.4%, p<0.001). Maximum temperature and contact force did not differ between groups (Figure 2). No acute periprocedural complications, including steam popping, occurred. Conclusion In this first in vivo comparative analysis, Bi-RFA demonstrated significantly higher baseline impedance than Uni-RFA. Despite lower delivered power, bipolar ablation achieved significantly greater absolute and relative impedance reduction.