Termination Without Global Propagation in Re-Entrant Ventricular Tachycardia: Electrophysiologic Characteristics and 3D-Electroanatomical Mapping Analysis.

Background: Termination of ventricular tachycardia (VT) by a pacing stimulus that does not generate a QRS complex (termination without global propagation [TWGP]) can be a marker for a critical re-entry circuit isthmus. However, the electrophysiologic and anatomic features of these sites and their relation to VT substrate defined by 3-dimensional electroanatomical maps (3D-EAM) remain unknown.

Objectives: This retrospective study aimed to characterize TWGP sites and their relation to VT substrate identified by 3D-EAM.

Methods: A total of 632 consecutive cases of catheter ablation for scar-related VT at 2 University medical centers were reviewed to identify TWGP.

Results: TWGP was observed 12 times at 11 different sites in 10 patients (5 ischemic cardiomyopathy). The TWGP stimulus fell immediately before or synchronous with the QRS in all cases, and evidence of local capture despite absence of a QRS complex was observed 6 times. In 5 sites, pacing after VT termination produced a QRS different than the VT. Four sites were in dense scar areas (<0.1 mV), and 6 in abnormal low voltage zone (0.1-1.5 mV). Additional mapping or ablation that abolished VT were consistent with the TWGP site being in a VT isthmus. A substrate marker for VT of late potentials, evoked delayed potentials, or slow conduction was present at 6 of 11 TWGP sites.

Conclusions: TWGP may be a marker for detecting a re-entry circuit isthmus that has escaped detection based on electrogram or pace mapping-based substrate mapping.