Limitation of Unipolar Electrograms in Guiding Successful RFCA of Idiopathic Ventricular Arrhythmias Associated With Discrete Pre‐Potential

OBJECTIVES: Activation mapping for idiopathic ventricular arrhythmias (IVAs) typically relies on identifying the earliest bipolar electrograms and unipolar electrograms characterized by an initial QS morphology preceding the intrinsic deflection. However, the utility of unipolar electrogram morphology, particularly when associated with discrete pre-potentials, in guiding IVA mapping is not well understood. METHODS: We retrospectively analyzed 537 patients who underwent successful radiofrequency catheter ablation (RFCA) for IVAs between March 2016 and August 2023. Among them, 23 patients (4.3%) exhibited discrete bipolar pre-potentials with an isoelectric line between the end of the discrete pre-potential and the onset of the QRS complex during IVAs at the successful RFCA site. These cases were included in this study. RESULTS: The time interval from the onset of the discrete pre-potential to the onset of the QRS complex was 66.4 ± 18.3 ms. The duration of the isoelectric line between the end of the discrete pre-potential and the onset of the QRS complex was 36.9 ± 13.6 ms. Unipolar electrograms associated with discrete pre-potentials exhibited an initial negative morphology in only 13 out of 23 patients (56.5%). In contrast, initial positive and isoelectric configurations in unipolar electrograms were observed in two patients (8.7%) and eight patients (34.8%), respectively. Perfect pace mapping was obtained in 21 patients (91.3%). RFCA was successful at the earliest site of the pre-potential within 3.5 ± 1.5 s in all 23 patients. During the 2.4 ± 1.2 years follow-up period, only one patient (4.3%) experienced a recurrence of clinical IVAs, with no complications reported during RFCA or follow-up. CONCLUSIONS: Unipolar electrograms show limited reliability in guiding the identification of IVAs origins compared to bipolar electrograms associated with discrete pre-potentials.