Functional Assessment of Ventricular Tachycardia Circuits and Their Underlying Substrate Using Automated Conduction Velocity Mapping.

Abstract

This study sought to describe the utility of automated conduction velocity mapping (ACVM) in ventricular tachycardia (VT) ablation. Identification of areas of slowed conduction velocity (CV) is critical to our understanding of VT circuits and their underlying substrate. Recently, an ACVM called Coherent Mapping (Biosense Webster Inc) has been developed for atrial mapping. However, its utility in VT mapping has not been described. Patients with paired high-density VT activation and substrate maps were included. ACVM was applied to paired VT activation and substrate maps to assess regional CV and activation patterns. A combination of ACVM, traditional local activation time maps, electrogram analysis, and off-line calculated CV using triangulation were used to characterize zones of slowed conduction during VT and in substrate mapping. Fifteen patients were included in the study. In all cases, ACVM identified slow CV within the putative VT isthmus, which colocalized to the VT isthmus identified with entrainment. The dimensions of the VT isthmus with local activation time mapping were 37.8 ± 13.7mm long and 8.7 ± 4.2mm wide. In comparison, ACVM produced an isthmus that was shorter (length: 25.1 ± 10.6mm; mean difference: 12.8; 95%CI: 7.5-18.0; P< 0.01) and wider (width: 18.8 ± 8.1mm; mean difference: 10.1; 95%CI: 6.1-14.2; P< 0.01). In VT, the CV using triangulation at the entrance (8.0 ± 3.6cm/s) and midisthmus (8.1 ± 4.3cm/s) was not significantly different (P = 0.92) but was significantly faster at the exit (16.2 ± 9.7cm/s; P< 0.01). In the paired substrate analysis, traditional local activation time isochronal mapping identified 6.3 ± 2.0 deceleration zones. In contrast, ACVM identified a median of 0 deceleration zones (IQR: 0-1; P< 0.01). ACVM is a novel complementary tool that can be used to accurately resolve complex VT circuits and identify slow conduction zones in VT but has limited accuracy in identifying slowed conduction during substrate-based mapping.