Temporal dynamics of deceleration zones during S3 isochronal mapping-guided VT ablation
P Bhagirath, T Rosseel, M Regany, F R Graterol, E Y A Ayauja-Lopez, R Pittorru, N Pierucci, S Vazquez-Calvo, E Guasch, L Mont, J Brugada, J M Tolosana, J B Guichard, A Porta-Sanchez, I Roca-LuqueAbstract
Background
Isochronal Late Activation Mapping (ILAM) identifies deceleration zones (DZs) as functional markers of slow conduction within ventricular scar and key targets for substrate-guided ventricular tachycardia (VT) ablation. However, the temporal behavior of DZs and the influence of pacing protocol on their detection remain insufficiently characterized. Previous work using conventional S1 pacing demonstrated that approximately 21% of DZs were not evident at baseline but appeared or shifted upon remapping, suggesting that single-drive pacing underestimates the functional substrate. The S3 pacing protocol may enhance slow-conduction provocation and enable more complete substrate delineation.
Objective
To characterize the evolution of DZs during substrate-based VT ablation using the S3 ILAM protocol and to quantify newly emergent or migrated DZs across sequential remaps.
Methods
Consecutive VT ablation procedures performed with the S3 ILAM protocol were analysed. Baseline and post-ablation maps were compared to classify DZs as abolished, persistent, migrated, or newly emerged. Migrated or newly emerged zones were collectively defined as dynamic DZs.
Results
A total of 48 baseline DZs were identified across 20 ablation procedures (2.4 ± 1.0 per case). After the first ablation set, 31 DZs (65%) were abolished, 13 (27%) persisted, 3 (6%) newly appeared, and 1 (2%) migrated, resulting in 92% of zones abolished or unchanged between mappings. Persistent DZs were mainly located in basal and septal regions, while newly emergent DZs appeared in basal-inferior and mid-anterior segments. Compared with S1-based mapping, the S3 protocol markedly reduced the rate of new or dynamic DZs, suggesting a more exhaustive functional substrate definition during initial mapping.
Conclusion
The S3 pacing protocol for ILAM yielded a very low proportion of newly emergent or migrated deceleration zones compared with conventional S1 pacing. By extending the pacing drive and unmasking concealed conduction delay, S3 ILAM provides a functionally more complete representation of the arrhythmogenic substrate and may reduce the need for iterative remapping during VT ablation.Three Patterns of Deceleration Zone