Key result
Lower bipolar voltage thresholds identify slow conduction isthmuses within dense scar in ~90% of patients.
Why the study?
Traditional voltage thresholds were set with older technology, whereas HD multipolar mapping suggests critical slow conduction channels may exist within conventionally inert dense scar.
Does using modified, lower bipolar voltage thresholds via HD catheters improve the identification of slow conduction channels within dense scar in patients undergoing VT ablation?
Observational (n=10)
Does using modified, lower bipolar voltage thresholds via HD catheters improve the identification of slow conduction channels within dense scar in patients undergoing VT ablation?
Using modified, lower bipolar voltage thresholds (0.05-0.5 mV) with high-density mapping catheters can unmask critical slow conduction channels within conventionally defined dense scar during VT ablation.
May inform scar-based VT ablation; leaves open need for larger prospective validation.
Background/Introduction Substrate modification via voltage mapping during SR is crucial for VT ablation. Traditional bipolar thresholds define scar (BZ: 0.5–1.5 mV; DS: <0.5 mV), but were set with older technology. HD multipolar mapping catheters significantly improve resolution, suggesting critical slow conduction channels (isthmuses) may exist within the conventionally inert dense scar. Purpose This pilot study assesses the feasibility and efficacy of using modified, lower bipolar voltage thresholds via HD catheters to localize slow conduction areas and critical VT isthmuses, even within the conventional dense scar. Methods EAM of the left ventricle was performed in consecutive patients undergoing VT ablation (Carto 3, Optrell HD catheter). Mapping used SR or RV-paced rhythm. Conventional thresholds were initially used. If the suspected VT exit was in a deep scar, a modified scale was applied, culminating in 0.05–0.5 mV. Gold standard for slow conduction was the presence of LAVAs, LPs, and deceleration zones. Results The series included 10 patients (70% M / 30% F; mean age 58.5 years). The arrhythmogenic substrate was primarily ischemic cardiomyopathy (70%). Substrate mapping showed endocardial involvement in 5 (50%) patients, epicardial involvement in 3 (30%), and both endo-epicardial involvement in 3 (30%). In 9 cases, the suspected VT exit was localized within the conventionally defined dense scar area. By utilizing the most aggressive modified scale (0.05 to 0.5 mV), we were able to clearly identify the area of slow conduction on isochronal maps, which correlated accurately with the critical isthmus of the inducible VT circuit. Specifically, this modified threshold allowed for the unmasking of low-amplitude, delayed electrograms within the traditional "electrically silent" dense scar region. During follow-up, VT recurrence was observed in 2 (20%) patients, but 0 deaths were recorded. Conclusion(s) The enhanced resolution of HD mapping challenges the historical definition of dense scar. Our pilot data demonstrate that utilizing modified, lower voltage thresholds during SR is feasible and necessary to accurately identify surviving myocyte bundles serving as slow conduction isthmuses within dense scar. New voltage cutoffs are required to redefine the VT substrate in the HD mapping era.Central Fiugre
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Gigli et al. (2026) conducted an observational in Ventricular tachycardia (n=10). Modified multipolar voltage map thresholds (0.05-0.5 mV) vs. Conventional bipolar thresholds was evaluated on Identification of slow conduction areas and critical VT isthmuses. Using modified, lower bipolar voltage thresholds (0.05-0.5 mV) during high-density mapping successfully identified slow conduction isthmuses within conventional dense scar in 9 of 10 patients.
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