Unipolar local activation time outperforms bipolar electrograms for localizing outflow tract premature ventricular contractions

Background Electrograms mapping is commonly used to guide the ablation of focal arrhythmias. However, its utility in guiding premature ventricular contractions (PVCs) ablation may be limited when the arrhythmic focus is intramural. We proposed a novel mapping strategy based on unipolar local activation time (UNI-WAVEFRONT, defined by −dV/dT) and compared its performance with conventional bipolar electrogram (BiEGM) mapping. Purpose To evaluate whether a unipolar local activation time–based strategy improves localization efficiency for outflow tract PVCs. Methods This single-center retrospective study included consecutive patients undergoing catheter ablation for RVOT-shaped PVC between March 2022 and December 2024. The RVOT-shaped PVCs were defined QS or rS in V1 lead. Patients treated during the first 3 months were assigned to the derivation cohort, in which the optimal cut-off value of the dV/dTmax-to-notch interval was determined using receiver operating characteristic analysis. Patients in the validation cohort were anatomically classified as V-RVOT group and V-RVOT plus groups. Within each subgroup, patients were stratified by mapping strategy (BiEGM vs. dV/dT). dV/dTmax-to-notch interval was defined as the time interval between the maximum negative dv/dt of the unipolar electrogram and the first notch of the unipolar signal. Propensity score matching was performed within each anatomical subgroup to reduce selection bias. Results 688 patients were enrolled. In the derivation cohort, a dV/dTmax-to-notch interval of 10 ms optimally discriminated RVOT from RVOT-plus origins (AUC 1.000; 95% confidence interval [CI], 1.000–1.000). In the validation cohort, the dV/dT-guided strategy significantly reduced procedural duration in both subgroups. In the V-RVOT group, procedure time decreased from 60.07 ± 27.04 to 41.96 ± 18.08 minutes (P < 0.0001; 95% CI 12.42–23.81). In the V-RVOT-plus group, procedure time decreased from 89.38 ± 35.74 to 64.67 ± 25.22 minutes (P < 0.0001; 95% CI 10.83–38.61). PVC recurrence rates were comparable between mapping strategies in both subgroups. Conclusions UNI-WAVEFRONT (−dV/dT) mapping improves procedural efficiency in outflow tract PVC ablation. A dV/dTmax-to-notch interval >10 ms suggests an intramural origin. This strategy significantly shortens procedural time without compromising clinical outcomes.Fig1.Flowchart of patient selection.