Post-infarct VT substrate ablation based on evoked delayed potential elimination as well-defined target : results from a prospective multicenter study
Authors: Evertz R , De Riva Silva M , Lukac P , Dekker L , Ouss A , Blauw Y , Mulder BA , Ter Bekke R , Vernooy K , Wijnmaalen AP , Kimura Y , Zeppenfeld K 
Published: May 2022

Abstract

Funding Acknowledgements
Type of funding sources: None.

Background
Substrate ablation is superior to approaches that target clinical and tolerated VTs in patients with post-myocardial infarction (MI) VT. Different substrate modification strategies have been reported. However, proposed ablation targets are prone to operator interpretation (e.g. abnormal electrograms). Accordingly, ablation results can also be operator dependent. Evoked delayed potentials (EDP) are a well-defined target. Elimination of EDP has been effective to prevent VT recurrence in a retrospective, single center cohort.

Aim
(1)To evaluate the outcome of EDP ablation in a prospective cohort of patients included on an intention-to-treat principle and (2)to assess the outcome of EDP ablation following one uniform protocol when performed in centers without prior experience with this strategy.

Methods
Consecutive patients referred for post-MI VT ablation were prospectively enrolled in one center with extensive experience in EDP ablation and 5 centers with no prior experience. Substrate mapping focused on EDP identification followed a uniform protocol across all centers. In brief, all electrograms located within the infarct area were analyzed during sinus rhythm, RV pacing at a fixed rate and during the application of one short-coupled RV extra (S2). Sites showing low-voltage, nearfield electrograms with &gt;10ms delay or block in response to S2 were categorized as EDP and targeted for ablation. After ablation, re-mapping to confirm EDP elimination and a complete stimulation protocol (up to 4 extra’s from RV and LV) were performed.

Results
131 patients (69±10 years, 87% men, 42% anterior MI, LVEF 33±11%, 70% NYHA II-III, 43% on amiodarone, 52% ≥1 ICD shock, 34% with electrical storm or incessant VT) were included. Multipolar catheters or catheters with micro-electrodes in the tip were used in 53%. The extra-stimulation protocol was systematically conducted in 127 (97% ) patients and in 121 (92%), EDPs were identified. EDPs were successfully eliminated in 117/121 (97%) patients. After 23 (IQR 14-35) min of RF, 101 (77%) patients were rendered non-inducible. Median procedural duration was 213 (IQR 180-267) min. During follow-up of 14 (IQR 8-19) months, 36 (27%) patients had VT recurrence and 14 (11%) died or received a LVAD. VT-free survival was 78% (CI95% 71-85) and 71% (CI95% 63-80) at 6 and 12 months follow-up. Of note, VT-free survival at 12 month was not significantly different between patients undergoing the procedure in centers with and without prior experience in EDP ablation (76% (CI95% 62-90) vs. 69% (CI95% 59-80); P=0.269).

Conclusion
In a large prospective cohort of patients with post-MI VT, substrate ablation based on EDP elimination resulted in excellent long-term outcome. Of importance, procedural outcomes were similar in centers with or without experience in EDP ablation, indicating that this approach can be easily reproduced by operators previously not familiar with the technique.