Modification of deceleration zones and late potentials after ventricular tachycardias substrate ablation
Authors: China P , Quinto L , Vio R , Vitale R , Marras E , Forlin E , Themistoclakis S 
Published: May 2024

Abstract

Introduction
Characterization of ventricular substrate is crucial during ventricular tachycardias (VT) ablation. Isochronal Late Activation Mapping (ILAM) is a recently introduced visualization tool that permit to identify areas of slow conduction (deceleration zones, DZs), these seems to well correlate with VT isthmuses. However, there are limited data about changes in this substrate after catheter ablations.

Purpose
To evaluate changes that occur to DZs and late potentials (LPs) after repeated ablative lesion sets.

Methods
High density voltage map and ILAM of the left ventricles (LV) during paced rhythm were performed in all cases. LV activation map was divided into 8 isochrones and DZ was defined as the presence of 3 isochrones within 1 cm-radius. LPs were defined as EGMs with late and fragmented components after the QRS. PES was performed at the beginning and at the end of the procedure. Each RF lesion set were applied with force-sensing irrigation catheter (target LSI 6-6.5) to abolish all the DZs and LPs discovered at baseline. After the first lesion set a re-map was performed looking for persistent DZs or LPs in the same LV segment (residual) or the appearance in a new ones (shift) in a 17-segment LV model; additional RF lesions and maps were performed only if DZs or LPs were still present in the last map.

Results
Of 28 VT cases considered, 9 patients with detailed LV maps and subsequent remaps were analyzed. Median age was 66 yo, 8 males, 7/9 with ischemic heart disease. In 7/9 patients clinical VTs were also induced and mapped. At baseline ILAM maps identified 24 DZs; after the first lesion set, 9 DZs were still appreciable at the same localization and 9 shifts to another LV segment (e.g. fig1). In 100% of patients at least one DZ was still appreciable at the first remap, while in 78% of patients a shift of the previous one was noted. At remap after a second lesion set 9 DZs were still present (3 residual, 6 shifts) in 33% of pts. Finally after a third lesion set only 2 DZs were still present in the same segment and then abolished. Furthermore, at baseline LPs were present in 28 LV segments, and after the first lesion set LPs were still present in 15 segments (9 residual, 6 new LPs). At first remap 78% of patients still showed LPs. After a second lesion set LPs were still visible in 6 segments (3 residual, 3 shift) in 22% of patients. In the third remap only in 2 segments could still be appreciated (1 residual, 1 shift) and finally were all abolished (summary in fig2). In 5/7 patients the clinical VT isthmus were identified in a DZ at baseline. At median FU of 6 months 7/9 patients has no VT recurrences, while there was one non-cardiovascular death.

Conclusions
Frequently DZs and LPs persistence is observed after first sets of lesions and additional RF deliveries are required for complete abolition. Remapping often demonstrates that both DZs and LPs move to other adjacent LV segments, likely where they were previously masked.Fig1Fig2