Objectives: To investigate whether the earliest retrograde activation during sinus rhythm -guided for left posterior fascicular ventricular tachycardia ablation further contributes to the identification of critical sites of VT reentry and whether this translates into a more effective ablation outcome in a cohort of patients undergoing VT ablation. Methods: This study retrospectively analyzed 86 consecutive patients (mean age 36.3AE5.9 years) referred for catheter ablation of electrocardiographically documented LPF VT. Programmed stimulation was performed to induce tachycardia, while mapping and ablation was aided by use of a 3D electroanatomical mapping system. Catheter ablation targeted the earliest potential suggestive of retrograde activation within the posterior Purkinje fiber network (retro-PP) recorded along the posterior mid-septal left ventricle during SR if LPF VT was noninducible. Results: 80 patients (45 men; mean age 34AE9 years) had inducible VTs. The mean tachycardia cycle length was 315AE33 ms. Overall, 75/86 (87%) patients underwent successful catheter ablation in SR targeting the earliest retro-PR. In none of the patients, ablation resulted in LPF block. No procedure-related complications occurred. Ablation was successful in all. After a median follow-up period of 2.9 (0.8-5.9) years, 81/86 (94%) patients were free from recurrent VT. Conclusions: In patients presenting with LPF VT, ablation of the earliest retro-PP along the posterior mid-septal LV during SR results in excellent long-term outcome during a median follow-up period of almost 2.9 years.

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