Long-term outcomes of ventricular tachycardia substrate ablation incorporating hidden slow conduction analysis

Background: Ventricular tachycardia substrate ablation (VTSA) incorporating hidden slow conduction (HSC) analysis allows further arrhythmic substrate identification.

Objective: The purpose of this study was to analyze whether the elimination of HSC electrograms (HSC-EGMs) during VTSA results in better short- and long-term outcomes.

Methods: Consecutive patients (N = 70; 63% ischemic; mean age 64 ± 14.6 years) undergoing VTSA were prospectively included. Bipolar EGMs with >3 deflections and duration <133 ms were considered as potential HSC-EGMs. Whenever a potential HSC-EGM was identified, double or triple ventricular extrastimuli were delivered. If a local potential showed up as a delayed component, it was annotated as HSC-EGM. Ablation was delivered at conducting channel entrances and HSC-EGMs. Radiofrequency time, ventricular tachycardia (VT) inducibility after VTSA, and VT/ventricular fibrillation recurrence at 24 months after the procedure were compared with data from a historical control group.

Results: A total of 5076 EGMs were analyzed; 1029 (20.2%) qualified as potential HSC-EGMs, and 475 of them were tagged as HSC-EGMs. Scars in patients with HSC-EGMs (n = 43 [61.4%]) were smaller (32.2 [17-58] cm² vs 85 [41-92.4] cm²; P = .006) and more heterogeneous (core/scar area ratio 0.15 [0.05-0.44] vs 0.44 [0.33-0.57]; P = .017); 32.4% of HSC-EGMs were located in normal voltage tissue. Patients undergoing VTSA incorporating HSC analysis required less radiofrequency time (15.6 [8-23.1] vs 23.9 [14.9-30.8]; P < .001) and had a lower rate of VT inducibility after VTSA (28.6% vs 52.9%; P = .003) than did the historical controls. Patients undergoing VTSA incorporating HSC analysis showed a higher 2-year VT/ventricular fibrillation-free survival (75.7% vs 58.8%; log-rank, P = .046) after VTSA.

Conclusion: VTSA incorporating HSC analysis allowed further arrhythmic substrate identification (especially in the border zone and normal voltage areas) and was associated with increased VTSA efficiency and better short- and long-term outcomes.