Functional Substrate Mapping in Ablation for Scar-Related Ventricular Tachycardia

Notably, most ventricular tachycardia (VT) episodes in patients with VT attributable to structural heart disease are not hemodynamically tolerated. Therefore, techniques for substrate mapping during stable intrinsic or paced rhythm have been developed that eliminate the need to induce VT. Moreover, advances in catheter technology, enabling high-density multi-electrode mapping of abnormal electrograms, have improved the ability of electrophysiologists to identify the substrate responsible for scar-related VT. In addition to the conventional identification of late potentials and local abnormal ventricular activity (LAVA), several substrate imaging approaches have been developed, including the identification of sites of conduction slowing via isochronal late activation mapping and the modification of wavefronts by changing the pacing site. Further, a new near-field algorithm provides a degree of objectivity to the previously subjective annotations of local potential timing. Additionally, changes in the substrate within the scar, specifically the induction of a line of block and subsequent alteration of a LAVA by decremental conduction, can identify functional abnormal ventricular activity that contributes to the development and maintenance of VT and can further improve the accuracy of substrate mapping. Novel cardiac magnetic resonance imaging and computed tomography analyses, facilitated by specialized software, also provide information for non-invasive estimation of the VT isthmus location. Therefore, continued clinical implementation of these techniques and technologies has the potential to improve safety, reduce the complexity, and expand the number of patients who can safely undergo VT ablation.