Introduction: Various ECG algorithms have been proposed to identify the origin of idiopathic outflow tract (OT)-ventricular arrhythmia (VA). However, electrocardiographic features of failed and recurrent right ventricular outflow tract (RVOT) ablation of idiopathic OT-VAs have not been clearly elucidated. Methods and results: A total of 264 consecutive patients (mean age: 44.0 ± 13.0 years, 96 male) undergoing RVOT ablation for OT-VAs with a transition ≥V3, including 241 patients (91.6%) with initially successful procedures and 23 patients (8.4%) with failed ablation. Detailed clinical characteristics and ECG features were analyzed and compared between the two groups. VAs with failed RVOT ablation had larger peak deflection index (PDI), longer V2 R wave duration (V2Rd), smaller V2 S wave amplitude, higher R/S ratio in V2, higher V3 R wave amplitude, and larger V2 transition ratio than those with successful ablation. Multivariate analysis demonstrated that PDI, V2Rd, V2 transition ratio, and pacemapping score acquired during mapping independently predicted failed ablation (P = 0.01, P = 0.01, P = 0.01, and P < 0.001, respectively). In 31 recurrent cases (12.8%) after initially successful ablation, multivariate Cox regression analysis showed that only the earliest activation time acquired during mapping predicted the recurrences after successful ablation (P = 0.001). The recurrent cases displayed different ECG features comparing with those with failed ablation. Conclusion: The electrocardiographic features of failed RVOT ablation of idiopathic OT-VAs with a transition ≥V3 were characterized by PDI, V2Rd, V2 transition ratio, and pacemapping score acquired during mapping, unlike the recurrent RVOT ablation.
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