Abstract Body (Do not enter title and authors here): Background:
Idiopathic left posterior fascicular ventricular tachycardia (LPF-VT) is commonly treated with radiofrequency ablation (RFA), where non-inducibility of VT post-ablation is the conventional procedural endpoint. However, the occurrence of repetitive ventricular responses (RVR)—defined as ablation-induced, non-sustained ventricular tachycardia (NSVT) with morphology matching the clinical VT—may indicate real-time lesion effectiveness, even during sinus rhythm. This study aimed to assess whether RVR serves as a reliable predictor of successful ablation and long-term outcomes.

Methods:
This retrospective study included 38 consecutive patients (mean age 30 ± 9 years; 84% male) with inducible LPF-VT who underwent RFA during sinus rhythm. Ablation targeted low-amplitude Purkinje-like potentials in the left posterior septum. RVR was defined as ≥3 beats of NSVT provoked by RF energy and matching the clinical VT QRS morphology. Patients were stratified based on the presence or absence of RVR. Procedural success (non-inducibility post-RFA) and VT recurrence during a mean 24-month follow-up were compared.

Results:
RVR was observed in 27 of 38 patients (71%). Acute procedural success was achieved in all patients. VT recurrence was significantly lower in the RVR-positive group (2 of 27; 7.4%) compared to the RVR-negative group (4 of 11; 36.4%). All RVR episodes showed QRS morphology identical to the clinical VT. Two transient complications (one ventricular fibrillation, one polymorphic VT) occurred without long-term sequelae. These findings align with the “thermal mapping” concept, suggesting RVR may reflect effective lesion formation.

Conclusion:
Repetitive ventricular responses during RFA of LPF-VT are associated with improved long-term outcomes and lower recurrence rates. When the induced NSVT matches the clinical VT morphology, RVR may serve as a valuable adjunctive intra-procedural marker of successful ablation. Incorporating RVR as a procedural indicator may enhance ablation guidance in patients with LPF-VT.