Background: In scar-related ventricular tachycardia (VT) ablation, conduction slowing area (CSA) has gained interest as a promising ablation target.
Objective: To investigate the relationship between the presence of CSA and VT isthmus detection.
Methods: A total of 22 (62 years, 4 females) patients who underwent VT ablation with high density sinus rhythm substrate mapping and pace mapping (PM) were enrolled. Isochronal late activation maps (ILAMs) were reconstructed for the analysis; all electrograms were annotated to the latest offset and total activation window was divided into 8 isochronal zones. CSA was defined as ≥ 70% narrowing of adjacent isochronal spacing. ILAMs were classified into 2 patterns with (type 1) or without (type 2) CSA, and compared whether pace map-based isthmus was identified.
Results: A total of 35 ILAMs were reconstructed; simultaneous endo- and epicardial mapping in the same procedure in 12 patients, LV or RV endocardial mapping in 7, and epicardial mapping in 4. Eighteen of 22 patients (82%) demonstrated type 1 ILAMs on at least one mapping surface, while 4 (18%) demonstrated type 2 only. VT isthmuses were identified in 22 of 28 target VTs (76%), and all but 1 isthmuses were on the type 1 ILAMs with the isthmus location closely related to the CSA. Patients with type1 CSA demonstrated better acute success (p < 0.01) and better mid-term (17months) free-from recurrence (p < 0.01).
Conclusion: CSA on ILAMs implied higher isthmus detection rate with better ablation outcome, while absence of CSA implied no identifiable arrhythmogenic substrate on the mapping surface. Presence of conduction slowing area can be a predictor of successful ablation on the mapping surface.