Variant of ventricular outflow tract ventricular arrhythmias requiring ablation from multiple sites: Intramural origin

Background: The optimal site of ablation of idiopathic left ventricular outflow tract (LVOT) ventricular arrhythmias (VAs) is challenging as activation mapping can reveal similar activation times in different anatomical sites, suggesting an intramural origin. Objective: We sought to assess whether in patients with intramural VAs and with multiple early activation sites (EASs), sequential ablation of all the early EASs could improve acute and long-term clinical outcomes. Methods: A total of 116 patients undergoing catheter ablation for symptomatic LVOT VAs were enrolled in this study. Thirty-nine patients (34%) were referred for a redo procedure, whereas the remaining presented for a first procedure. Mapping was performed manually in 86 cases (74%) and with a magnetic robotic system (Niobe, Stereotaxis, St. Louis, MO) in the remainder of the cases. Results: Of the 116 patients, 15 (13%) were found to have multiple sites of equally early activation. In patients with multiple EASs, the mean pre-QRS activation time was significantly less than in patients with a single EASs (−26 ± 3 ms vs −38 ± 6 ms; P <.005). Sequential ablation of all the EASs was possible in 14 patients (93%), resulting in complete arrhythmia suppression. After a mean follow-up of 21 ± 5 months, all patients with successful ablation of all multiple early EASs remained free from clinical VAs. Conclusion: Intramural LVOT VAs manifesting with multiple EASs require ablation at all sites to achieve acute and long-term success, particularly if none of the EASs is > -30ms pre-QRS activation time.