Evaluation of noninvasive isochronal late activation mapping in scar-related ventricular tachycardia with electrocardiographic imaging against contact mapping

BACKGROUND: Deceleration zones (DZs) represent important ablation targets in scar-related ventricular tachycardias (VTs). Novel electrocardiographic imaging (ECGI) techniques could identify DZs instantly and noninvasively. OBJECTIVE: We aimed to evaluate a novel ECGI last deflection detection algorithm for noninvasive isochronal late activation substrate mapping in scar-related VT procedures and compare against electroanatomic mapping (EAM) as gold-standard. METHODS: Prospectively recruited scar-related VT ablation patients underwent contact and ECGI mapping. Sinus rhythm or right ventricular paced baseline maps were acquired, temporal signal averaging was performed, and unipolar electrograms were reconstructed. Local activation time was annotated to the last negative deflection before T wave. Isochronal late activation substrate maps were generated by dividing activation maps in 8 and 12 isochronal zones. Number and location of ECGI late activating areas and ECGI DZs were compared with EAM on a segmental basis. RESULTS: Forty-seven patients (27.7% ischemic, 72.3% nonischemic) were studied; epicardial data was acquired in 30 (63.8%). No significant difference in the absolute late activating areas was identified on ECGI vs EAM (P = .161); latest electrogram was significantly later on EAM. ECGI yielded a sensitivity of 68% and specificity of 95% to detect late activation using EAM as gold-standard. EAM identified DZs in 91.5% and ECGI in 93.6% of patients (P = .5). ECGI detected significantly more DZs per map than EAM (2.5 ± 1.2 vs 1.2 ± 0.8; P < .001) but with less steep activation gradients (P = .002). Sensitivity for ECGI DZ mapping was 46.8% and specificity was 90.6% in the context of a high number of total segments and preemptive exclusion of interpolated and artificial DZs (identified in 95.7%). CONCLUSION: ECGI with last negative deflection detects late activation zones in most cases with a moderate sensitivity. Detailed functional substrate mapping including accurate localization of local DZs remains challenging, with low sensitivity, precluding its clinical use for this indication in its current form.