Abstract
Isolated late activation mappings (ILAMs) can identify possible ventricular tachycardia (VT) isthmus during sinus rhythm (SR). The interference of far-field potentials at the deceleration zone (DZ) may cause misleading results. Electrogram peak frequency (PF) has the potential to discriminate between far-field and near-field signals. We aimed to identify the VT isthmus by applying PF over SR substrate maps. Ten patients with scar-related VT (ischemic/nonischemic cardiomyopathy 6/4) were studied. VT isthmuses were identified based on the activation maps, entrainment, and ablation results during tachycardia. The accuracy of PF maps in detecting potential VT isthmuses during SR before ablation was assessed. Twelve VT isthmuses were identified. The bipolar mean voltage and PF of isthmus areas over the pre-ablation SR map were 0.25 ± 0.12 mV and 307.5 ± 54.3 Hz, respectively. All isthmuses were within low voltage zones (LVZ) with PF of more than 250Hz. Before ablation, 11 of 25 (44.0%) DZs identified from ILAM by annotating the last deflection EGMs in LVZ were compatible with VT isthmuses (mean PF 311.0 ± 66.0Hz); mean PF of DZs which were not isthmus locations was 177.6 ± 51.5 Hz. There were 12 of 15 (80.0%) DZs on ILAMs constructed by annotating PF EGMs compatible with VT isthmuses. VT isthmus is mostly located in LVZ (<0.5 mV) with PF value over 250Hz from pre-ablation SR maps. The DZs during SR with a low PF could be bystanders. Identifying DZs by annotating EGMs with PF, rather than last deflections, is better to discriminate critical VT substrates.
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