Evaluation of Non-Invasive Isochronal Late Activation Mapping in Scar Related VT with Electrocardiographic Imaging against Contact Mapping.

Abstract

Background: Deceleration zones (DZ) represent important ablation targets in scar-related ventricular tachycardias (VT). Novel Electrocardiographic Imaging (ECGI) techniques could identify DZs instantly and non-invasively.

Objective: Evaluate a novel ECGI last deflection detection algorithm for non-invasive isochronal late activation substrate mapping (iLAM) in scar-related VT procedures against electroanatomical mapping (EAM) METHODS: Prospectively recruited scar-related VT ablation patients underwent contact and ECGI mapping. SR or RV-paced baseline maps were acquired, temporal signal averaging performed and unipolar electrograms (EGM) reconstructed. Local activation time was annotated to the last negative deflection (LD) before T-wave. iLAMs were generated by dividing activation maps in 8 and 12 isochronal zones. Number and location of ECGI late activation areas (LAA) and ECGI-DZ were compared to EAM on a segmental basis.

Results: 47 patients (27.7% ischemic, 72.3% non-ischemic) were studied, epicardial data was acquired in 30 (63.8%). No significant difference in the absolute LAAs were identified on ECGI versus EAM (p=0.161), latest EGM was significantly later on EAM. ECGI late activation mapping yielded a sensitivity of 68% and specificity of 95%. EAM identified DZs in 91.5%, ECGI in 93.6% of patients (p 0.5). ECGI detected significant more DZs per map than EAM (2.5±1.2 vs 1.2±0.8, p <0.001) but less steep activation gradients (p 0.002). Sensitivity for ECGI-DZ mapping was 46.8%, specificity 90.6% in the context of a high number of total segments, and pre-emptive exclusion of interpolated/artificial DZ (identified in 95.7%).

Conclusion: ECGI with LD detects late activation zones in the majority of cases with a moderate sensitivity. Yet, detailed functional substrate mapping including accurate localisation of local DZs remains challenging with low sensitivity precluding its clinical use for this indication in its current form.